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Change the owner of "$JBOSS_CONSOLE_LOG" to "$JBOSS_USER"

chown $JBOSS_USER $JBOSS_CONSOLE_LOG

['chown']

Output a Bash command to accomplish the following task. Task: Change the owner of "$JBOSS_CONSOLE_LOG" to "$JBOSS_USER" Bash Command:<START>chown $JBOSS_USER $JBOSS_CONSOLE_LOG<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner of "$JBOSS_CONSOLE_LOG" to "$JBOSS_USER" Bash Command:<START>chown $JBOSS_USER $JBOSS_CONSOLE_LOG<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of "$JBOSS_CONSOLE_LOG" to "$JBOSS_USER" Bash Command:<START>chown $JBOSS_USER $JBOSS_CONSOLE_LOG<END>

Change the owner of "/var/www/html/mysite/images/" to "nobody"

sudo chown nobody /var/www/html/mysite/images/

['chown', 'sudo']

Output a Bash command to accomplish the following task. Task: Change the owner of "/var/www/html/mysite/images/" to "nobody" Bash Command:<START>sudo chown nobody /var/www/html/mysite/images/<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n # sudo\n\n> Executes a single command as the superuser or another user.\n> More information: <https://www.sudo.ws/sudo.html>.\n\n- Run a command as the superuser:\n\n`sudo {{less /var/log/syslog}}`\n\n- Edit a file as the superuser with your default editor:\n\n`sudo --edit {{/etc/fstab}}`\n\n- Run a command as another user and/or group:\n\n`sudo --user={{user}} --group={{group}} {{id -a}}`\n\n- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):\n\n`sudo !!`\n\n- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login`\n\n- Launch the default shell with superuser privileges without changing the environment:\n\n`sudo --shell`\n\n- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login --user={{user}}`\n\n- List the allowed (and forbidden) commands for the invoking user:\n\n`sudo --list`\n Task: Change the owner of "/var/www/html/mysite/images/" to "nobody" Bash Command:<START>sudo chown nobody /var/www/html/mysite/images/<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sudo(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sudo(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON SUDO(8) System Manager's Manual SUDO(8) NAME top sudo, sudoedit execute a command as another user SYNOPSIS top sudo -h | -K | -k | -V sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command [arg ...]] sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] [VAR=value] [-i | -s] [command [arg ...]] sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] file ... DESCRIPTION top allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy. supports a plugin architecture for security policies, auditing, and input/output logging. Third parties can develop and distribute their own plugins to work seamlessly with the front- end. The default security policy is sudoers, which is configured via the file /etc/sudoers, or via LDAP. See the Plugins section for more information. The security policy determines what privileges, if any, a user has to run . The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific; the default password prompt timeout for the sudoers security policy is 5 minutes. Security policies may support credential caching to allow the user to run again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running with the -v option, a user can update the cached credentials without running a command. On systems where is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced. When invoked as sudoedit, the -e option (described below), is implied. Security policies and audit plugins may log successful and failed attempts to run . If an I/O plugin is configured, the running command's input and output may be logged as well. The options are as follows: -A, --askpass Normally, if requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example: # Path to askpass helper program Path askpass /usr/X11R6/bin/ssh-askpass If no askpass program is available, will exit with an error. -B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used. -b, --background Run the given command in the background. It is not possible to use shell job control to manipulate background processes started by . Most interactive commands will fail to work properly in background mode. -C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, will close all open file descriptors other than standard input, standard output, and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option. -D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory. -E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment. --preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times. -e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken: 1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used. 3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy: Symbolic links may not be edited (version 1.8.15 and higher). Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher). Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher). Users are never allowed to edit device special files. If the specified file does not exist, it will be created. Unlike most commands run by sudo, the editor is run with the invoking user's environment unmodified. If the temporary file becomes empty after editing, the user will be prompted before it is installed. If, for some reason, is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file. -g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the # character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the # be escaped with a backslash (\). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use. -H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior. -h, --help Display a short help message to the standard output and exit. -h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. The sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host. -i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login- specific resource files such as .profile, .bash_profile, or .login will be read by the shell. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use. -K, --remove-timestamp Similar to the -k option, except that it removes every cached credential for the user, regardless of the terminal or parent process ID. The next time is run, a password must be entered if the security policy requires authentication. It is not possible to use the -K option in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching. -k, --reset-timestamp When used without a command, invalidates the user's cached credentials for the current session. The next time is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with commands run in a different terminal session. See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke permissions from a .logout file. When used in conjunction with a command or an option that may require a password, this option will cause to ignore the user's cached credentials. As a result, will prompt for a password (if one is required by the security policy) and will not update the user's cached credentials. Not all security policies support credential caching. -l, --list If no command is specified, list the privileges for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format. If a command is specified and is permitted by the security policy for the invoking user (or the, user specified by the -U option) on the current host, the fully-qualified path to the command is displayed along with any args. If -l is specified more than once (and the security policy supports it), the matching rule is displayed in a verbose format along with the command. If a command is specified but not allowed by the policy, will exit with a status value of 1. -N, --no-update Do not update the user's cached credentials, even if the user successfully authenticates. Unlike the -k flag, existing cached credentials are used if they are valid. To detect when the user's cached credentials are valid (or when no authentication is required), the following can be used: sudo -Nnv Not all security policies support credential caching. -n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, will display an error message and exit. -P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user. -p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent (%) escape sequences are supported by the sudoers policy: %H expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in sudoers(5)) %h expanded to the local host name without the domain name %p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5)) %U expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified) %u expanded to the invoking user's login name %% two consecutive % characters are collapsed into a single % character The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers. -R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory. -S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device. -s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. -U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. When using the sudoers policy, the -U option is restricted to the root user and users with either the list priviege for the specified user or the ability to run any command as root or user on the current host. -T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the user's ability to set timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled. -u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the # character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the # be escaped with a backslash (\). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this. -V, --version Print the version string as well as the version string of any configured plugins. If the invoking user is already root, the -V option will display the options passed to configure when was built; plugins may display additional information such as default options. -v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials. -- The -- is used to delimit the end of the options. Subsequent options are passed to the command. Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input. Environment variables to be set for the command may also be passed as options to in the form VAR=value, for example LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be subject to restrictions imposed by the security policy plugin. The sudoers policy subjects environment variables passed as options to the same restrictions as existing environment variables with one important difference. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information. COMMAND EXECUTION top When executes a command, the security policy specifies the execution environment for the command. Typically, the real and effective user and group and IDs are set to match those of the target user, as specified in the password database, and the group vector is initialized based on the group database (unless the -P option was specified). The following parameters may be specified by security policy: real and effective user-ID real and effective group-ID supplementary group-IDs the environment list current working directory file creation mode mask (umask) scheduling priority (aka nice value) Process model There are two distinct ways can run a command. If an I/O logging plugin is configured to log terminal I/O, or if the security policy explicitly requests it, a new pseudo-terminal (pty) is allocated and fork(2) is used to create a second process, referred to as the monitor. The monitor creates a new terminal session with itself as the leader and the pty as its controlling terminal, calls fork(2) again, sets up the execution environment as described above, and then uses the execve(2) system call to run the command in the child process. The monitor exists to relay job control signals between the user's terminal and the pty the command is being run in. This makes it possible to suspend and resume the command normally. Without the monitor, the command would be in what POSIX terms an orphaned process group and it would not receive any job control signals from the kernel. When the command exits or is terminated by a signal, the monitor passes the command's exit status to the main process and exits. After receiving the command's exit status, the main process passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugin, and exits. This mode is the default for sudo versions 1.9.14 and above when using the sudoers policy. If no pty is used, calls fork(2), sets up the execution environment as described above, and uses the execve(2) system call to run the command in the child process. The main process waits until the command has completed, then passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugins, and exits. As a special case, if the policy plugin does not define a close function, will execute the command directly instead of calling fork(2) first. The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled. Both pam_session and pam_setcred are enabled by default on systems using PAM. This mode is the default for sudo versions prior to 1.9.14 when using the sudoers policy. On systems that use PAM, the security policy's close function is responsible for closing the PAM session. It may also log the command's exit status. Signal handling When the command is run as a child of the process, will relay signals it receives to the command. The SIGINT and SIGQUIT signals are only relayed when the command is being run in a new pty or when the signal was sent by a user process, not the kernel. This prevents the command from receiving SIGINT twice each time the user enters control-C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by . As a special case, will not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) utility sends SIGTERM to all non-system processes other than itself before rebooting the system. This prevents from relaying the SIGTERM signal it received back to reboot(8), which might then exit before the system was actually rebooted, leaving it in a half-dead state similar to single user mode. Note, however, that this check only applies to the command run by and not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via may cause the system to end up in this undefined state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the command and the calling process). Plugins Plugins may be specified via Plugin directives in the sudo.conf(5) file. They may be loaded as dynamic shared objects (on systems that support them), or compiled directly into the binary. If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, will use sudoers(5) for the policy, auditing, and I/O logging plugins. See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for more information about the plugin architecture. EXIT VALUE top Upon successful execution of a command, the exit status from will be the exit status of the program that was executed. If the command terminated due to receipt of a signal, will send itself the same signal that terminated the command. If the -l option was specified without a command, will exit with a value of 0 if the user is allowed to run and they authenticated successfully (as required by the security policy). If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by the security policy, otherwise it will be 1. If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, exits with a value of 1. In the latter case, the error string is printed to the standard error. If cannot stat(2) one or more entries in the user's PATH, an error is printed to the standard error. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat(2) to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. SECURITY NOTES top tries to be safe when executing external commands. To prevent command spoofing, checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the program that executes. Users should never be granted privileges to execute files that are writable by the user or that reside in a directory that is writable by the user. If the user can modify or replace the command there is no way to limit what additional commands they can run. By default, will only log the command it explicitly runs. If a user runs a command such as sudo su or sudo sh, subsequent commands run from that shell are not subject to sudo's security policy. The same is true for commands that offer shell escapes (including most editors). If I/O logging is enabled, subsequent commands will have their input and/or output logged, but there will not be traditional logs for those commands. Because of this, care must be taken when giving users access to commands via to verify that the command does not inadvertently give the user an effective root shell. For information on ways to address this, see the Preventing shell escapes section in sudoers(5). To prevent the disclosure of potentially sensitive information, disables core dumps by default while it is executing (they are re-enabled for the command that is run). This historical practice dates from a time when most operating systems allowed set-user-ID processes to dump core by default. To aid in debugging crashes, you may wish to re-enable core dumps by setting disable_coredump to false in the sudo.conf(5) file as follows: Set disable_coredump false See the sudo.conf(5) manual for more information. ENVIRONMENT top utilizes the following environment variables. The security policy has control over the actual content of the command's environment. EDITOR Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set. MAIL Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is present in the env_keep list). HOME Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the env_keep list. LOGNAME Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list). PATH May be overridden by the security policy. SHELL Used to determine shell to run with -s option. SUDO_ASKPASS Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified. SUDO_COMMAND Set to the command run by sudo, including any args. The args are truncated at 4096 characters to prevent a potential execution error. SUDO_EDITOR Default editor to use in -e (sudoedit) mode. SUDO_GID Set to the group-ID of the user who invoked sudo. SUDO_PROMPT Used as the default password prompt unless the -p option was specified. SUDO_PS1 If set, PS1 will be set to its value for the program being run. SUDO_UID Set to the user-ID of the user who invoked sudo. SUDO_USER Set to the login name of the user who invoked sudo. USER Set to the same value as LOGNAME, described above. VISUAL Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set. FILES top /etc/sudo.conf front-end configuration EXAMPLES top The following examples assume a properly configured security policy. To get a file listing of an unreadable directory: $ sudo ls /usr/local/protected To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root: $ sudo -u yaz ls ~yaz To edit the index.html file as user www: $ sudoedit -u www ~www/htdocs/index.html To view system logs only accessible to root and users in the adm group: $ sudo -g adm more /var/log/syslog To run an editor as jim with a different primary group: $ sudoedit -u jim -g audio ~jim/sound.txt To shut down a machine: $ sudo shutdown -r +15 "quick reboot" To make a usage listing of the directories in the /home partition. The commands are run in a sub-shell to allow the cd command and file redirection to work. $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" DIAGNOSTICS top Error messages produced by include: editing files in a writable directory is not permitted By default, sudoedit does not permit editing a file when any of the parent directories are writable by the invoking user. This avoids a race condition that could allow the user to overwrite an arbitrary file. See the sudoedit_checkdir option in sudoers(5) for more information. editing symbolic links is not permitted By default, sudoedit does not follow symbolic links when opening files. See the sudoedit_follow option in sudoers(5) for more information. effective uid is not 0, is sudo installed setuid root? was not run with root privileges. The binary must be owned by the root user and have the set-user-ID bit set. Also, it must not be located on a file system mounted with the nosuid option or on an NFS file system that maps uid 0 to an unprivileged uid. effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges? was not run with root privileges. The binary has the proper owner and permissions but it still did not run with root privileges. The most common reason for this is that the file system the binary is located on is mounted with the nosuid option or it is an NFS file system that maps uid 0 to an unprivileged uid. fatal error, unable to load plugins An error occurred while loading or initializing the plugins specified in sudo.conf(5). invalid environment variable name One or more environment variable names specified via the -E option contained an equal sign (=). The arguments to the -E option should be environment variable names without an associated value. no password was provided When tried to read the password, it did not receive any characters. This may happen if no terminal is available (or the -S option is specified) and the standard input has been redirected from /dev/null. a terminal is required to read the password needs to read the password but there is no mechanism available for it to do so. A terminal is not present to read the password from, has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the sudo.conf(5) file or the SUDO_ASKPASS environment variable. no writable temporary directory found sudoedit was unable to find a usable temporary directory in which to store its intermediate files. The no new privileges flag is set, which prevents sudo from running as root. was run by a process that has the Linux no new privileges flag is set. This causes the set-user-ID bit to be ignored when running an executable, which will prevent from functioning. The most likely cause for this is running within a container that sets this flag. Check the documentation to see if it is possible to configure the container such that the flag is not set. sudo must be owned by uid 0 and have the setuid bit set was not run with root privileges. The binary does not have the correct owner or permissions. It must be owned by the root user and have the set-user-ID bit set. sudoedit is not supported on this platform It is only possible to run sudoedit on systems that support setting the effective user-ID. timed out reading password The user did not enter a password before the password timeout (5 minutes by default) expired. you do not exist in the passwd database Your user-ID does not appear in the system passwd database. you may not specify environment variables in edit mode It is only possible to specify environment variables when running a command. When editing a file, the editor is run with the user's environment unmodified. SEE ALSO top su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8) HISTORY top See the HISTORY.md file in the distribution (https://www.sudo.ws/about/history/) for a brief history of sudo. AUTHORS top Many people have worked on over the years; this version consists of code written primarily by: Todd C. Miller See the CONTRIBUTORS.md file in the distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed to . CAVEATS top There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via . Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with the sudoers(5) plugin's noexec functionality. It is not meaningful to run the cd command directly via sudo, e.g., $ sudo cd /usr/local/protected since when the command exits the parent process (your shell) will still be the same. The -D option can be used to run a command in a specific directory. Running shell scripts via can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, set-user-ID shell scripts are generally safe). BUGS top If you believe you have found a bug in , you can submit a bug report at https://bugzilla.sudo.ws/ SUPPORT top Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives. DISCLAIMER top is provided AS IS and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE.md file distributed with or https://www.sudo.ws/about/license/ for complete details. COLOPHON top This page is part of the sudo (execute a command as another user) project. Information about the project can be found at https://www.sudo.ws/. If you have a bug report for this manual page, see https://bugzilla.sudo.ws/. This page was obtained from the project's upstream Git repository https://github.com/sudo-project/sudo on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Sudo 1.9.15p4 August 9, 2023 SUDO(8) Pages that refer to this page: homectl(1), journalctl(1), localectl(1), loginctl(1), machinectl(1), portablectl(1), setpriv(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), uid0(1), userdbctl(1), nsswitch.conf(5), credentials(7), systemd-tmpfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of "/var/www/html/mysite/images/" to "nobody" Bash Command:<START>sudo chown nobody /var/www/html/mysite/images/<END>

Change the owner of "/var/www/html/mysite/tmp_file_upload/" to "nobody"

sudo chown nobody /var/www/html/mysite/tmp_file_upload/

['chown', 'sudo']

Output a Bash command to accomplish the following task. Task: Change the owner of "/var/www/html/mysite/tmp_file_upload/" to "nobody" Bash Command:<START>sudo chown nobody /var/www/html/mysite/tmp_file_upload/<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n # sudo\n\n> Executes a single command as the superuser or another user.\n> More information: <https://www.sudo.ws/sudo.html>.\n\n- Run a command as the superuser:\n\n`sudo {{less /var/log/syslog}}`\n\n- Edit a file as the superuser with your default editor:\n\n`sudo --edit {{/etc/fstab}}`\n\n- Run a command as another user and/or group:\n\n`sudo --user={{user}} --group={{group}} {{id -a}}`\n\n- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):\n\n`sudo !!`\n\n- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login`\n\n- Launch the default shell with superuser privileges without changing the environment:\n\n`sudo --shell`\n\n- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login --user={{user}}`\n\n- List the allowed (and forbidden) commands for the invoking user:\n\n`sudo --list`\n Task: Change the owner of "/var/www/html/mysite/tmp_file_upload/" to "nobody" Bash Command:<START>sudo chown nobody /var/www/html/mysite/tmp_file_upload/<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sudo(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sudo(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON SUDO(8) System Manager's Manual SUDO(8) NAME top sudo, sudoedit execute a command as another user SYNOPSIS top sudo -h | -K | -k | -V sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command [arg ...]] sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] [VAR=value] [-i | -s] [command [arg ...]] sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] file ... DESCRIPTION top allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy. supports a plugin architecture for security policies, auditing, and input/output logging. Third parties can develop and distribute their own plugins to work seamlessly with the front- end. The default security policy is sudoers, which is configured via the file /etc/sudoers, or via LDAP. See the Plugins section for more information. The security policy determines what privileges, if any, a user has to run . The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific; the default password prompt timeout for the sudoers security policy is 5 minutes. Security policies may support credential caching to allow the user to run again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running with the -v option, a user can update the cached credentials without running a command. On systems where is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced. When invoked as sudoedit, the -e option (described below), is implied. Security policies and audit plugins may log successful and failed attempts to run . If an I/O plugin is configured, the running command's input and output may be logged as well. The options are as follows: -A, --askpass Normally, if requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example: # Path to askpass helper program Path askpass /usr/X11R6/bin/ssh-askpass If no askpass program is available, will exit with an error. -B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used. -b, --background Run the given command in the background. It is not possible to use shell job control to manipulate background processes started by . Most interactive commands will fail to work properly in background mode. -C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, will close all open file descriptors other than standard input, standard output, and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option. -D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory. -E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment. --preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times. -e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken: 1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used. 3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy: Symbolic links may not be edited (version 1.8.15 and higher). Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher). Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher). Users are never allowed to edit device special files. If the specified file does not exist, it will be created. Unlike most commands run by sudo, the editor is run with the invoking user's environment unmodified. If the temporary file becomes empty after editing, the user will be prompted before it is installed. If, for some reason, is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file. -g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the # character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the # be escaped with a backslash (\). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use. -H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior. -h, --help Display a short help message to the standard output and exit. -h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. The sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host. -i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login- specific resource files such as .profile, .bash_profile, or .login will be read by the shell. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use. -K, --remove-timestamp Similar to the -k option, except that it removes every cached credential for the user, regardless of the terminal or parent process ID. The next time is run, a password must be entered if the security policy requires authentication. It is not possible to use the -K option in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching. -k, --reset-timestamp When used without a command, invalidates the user's cached credentials for the current session. The next time is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with commands run in a different terminal session. See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke permissions from a .logout file. When used in conjunction with a command or an option that may require a password, this option will cause to ignore the user's cached credentials. As a result, will prompt for a password (if one is required by the security policy) and will not update the user's cached credentials. Not all security policies support credential caching. -l, --list If no command is specified, list the privileges for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format. If a command is specified and is permitted by the security policy for the invoking user (or the, user specified by the -U option) on the current host, the fully-qualified path to the command is displayed along with any args. If -l is specified more than once (and the security policy supports it), the matching rule is displayed in a verbose format along with the command. If a command is specified but not allowed by the policy, will exit with a status value of 1. -N, --no-update Do not update the user's cached credentials, even if the user successfully authenticates. Unlike the -k flag, existing cached credentials are used if they are valid. To detect when the user's cached credentials are valid (or when no authentication is required), the following can be used: sudo -Nnv Not all security policies support credential caching. -n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, will display an error message and exit. -P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user. -p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent (%) escape sequences are supported by the sudoers policy: %H expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in sudoers(5)) %h expanded to the local host name without the domain name %p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5)) %U expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified) %u expanded to the invoking user's login name %% two consecutive % characters are collapsed into a single % character The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers. -R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory. -S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device. -s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. -U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. When using the sudoers policy, the -U option is restricted to the root user and users with either the list priviege for the specified user or the ability to run any command as root or user on the current host. -T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the user's ability to set timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled. -u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the # character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the # be escaped with a backslash (\). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this. -V, --version Print the version string as well as the version string of any configured plugins. If the invoking user is already root, the -V option will display the options passed to configure when was built; plugins may display additional information such as default options. -v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials. -- The -- is used to delimit the end of the options. Subsequent options are passed to the command. Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input. Environment variables to be set for the command may also be passed as options to in the form VAR=value, for example LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be subject to restrictions imposed by the security policy plugin. The sudoers policy subjects environment variables passed as options to the same restrictions as existing environment variables with one important difference. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information. COMMAND EXECUTION top When executes a command, the security policy specifies the execution environment for the command. Typically, the real and effective user and group and IDs are set to match those of the target user, as specified in the password database, and the group vector is initialized based on the group database (unless the -P option was specified). The following parameters may be specified by security policy: real and effective user-ID real and effective group-ID supplementary group-IDs the environment list current working directory file creation mode mask (umask) scheduling priority (aka nice value) Process model There are two distinct ways can run a command. If an I/O logging plugin is configured to log terminal I/O, or if the security policy explicitly requests it, a new pseudo-terminal (pty) is allocated and fork(2) is used to create a second process, referred to as the monitor. The monitor creates a new terminal session with itself as the leader and the pty as its controlling terminal, calls fork(2) again, sets up the execution environment as described above, and then uses the execve(2) system call to run the command in the child process. The monitor exists to relay job control signals between the user's terminal and the pty the command is being run in. This makes it possible to suspend and resume the command normally. Without the monitor, the command would be in what POSIX terms an orphaned process group and it would not receive any job control signals from the kernel. When the command exits or is terminated by a signal, the monitor passes the command's exit status to the main process and exits. After receiving the command's exit status, the main process passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugin, and exits. This mode is the default for sudo versions 1.9.14 and above when using the sudoers policy. If no pty is used, calls fork(2), sets up the execution environment as described above, and uses the execve(2) system call to run the command in the child process. The main process waits until the command has completed, then passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugins, and exits. As a special case, if the policy plugin does not define a close function, will execute the command directly instead of calling fork(2) first. The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled. Both pam_session and pam_setcred are enabled by default on systems using PAM. This mode is the default for sudo versions prior to 1.9.14 when using the sudoers policy. On systems that use PAM, the security policy's close function is responsible for closing the PAM session. It may also log the command's exit status. Signal handling When the command is run as a child of the process, will relay signals it receives to the command. The SIGINT and SIGQUIT signals are only relayed when the command is being run in a new pty or when the signal was sent by a user process, not the kernel. This prevents the command from receiving SIGINT twice each time the user enters control-C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by . As a special case, will not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) utility sends SIGTERM to all non-system processes other than itself before rebooting the system. This prevents from relaying the SIGTERM signal it received back to reboot(8), which might then exit before the system was actually rebooted, leaving it in a half-dead state similar to single user mode. Note, however, that this check only applies to the command run by and not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via may cause the system to end up in this undefined state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the command and the calling process). Plugins Plugins may be specified via Plugin directives in the sudo.conf(5) file. They may be loaded as dynamic shared objects (on systems that support them), or compiled directly into the binary. If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, will use sudoers(5) for the policy, auditing, and I/O logging plugins. See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for more information about the plugin architecture. EXIT VALUE top Upon successful execution of a command, the exit status from will be the exit status of the program that was executed. If the command terminated due to receipt of a signal, will send itself the same signal that terminated the command. If the -l option was specified without a command, will exit with a value of 0 if the user is allowed to run and they authenticated successfully (as required by the security policy). If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by the security policy, otherwise it will be 1. If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, exits with a value of 1. In the latter case, the error string is printed to the standard error. If cannot stat(2) one or more entries in the user's PATH, an error is printed to the standard error. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat(2) to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. SECURITY NOTES top tries to be safe when executing external commands. To prevent command spoofing, checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the program that executes. Users should never be granted privileges to execute files that are writable by the user or that reside in a directory that is writable by the user. If the user can modify or replace the command there is no way to limit what additional commands they can run. By default, will only log the command it explicitly runs. If a user runs a command such as sudo su or sudo sh, subsequent commands run from that shell are not subject to sudo's security policy. The same is true for commands that offer shell escapes (including most editors). If I/O logging is enabled, subsequent commands will have their input and/or output logged, but there will not be traditional logs for those commands. Because of this, care must be taken when giving users access to commands via to verify that the command does not inadvertently give the user an effective root shell. For information on ways to address this, see the Preventing shell escapes section in sudoers(5). To prevent the disclosure of potentially sensitive information, disables core dumps by default while it is executing (they are re-enabled for the command that is run). This historical practice dates from a time when most operating systems allowed set-user-ID processes to dump core by default. To aid in debugging crashes, you may wish to re-enable core dumps by setting disable_coredump to false in the sudo.conf(5) file as follows: Set disable_coredump false See the sudo.conf(5) manual for more information. ENVIRONMENT top utilizes the following environment variables. The security policy has control over the actual content of the command's environment. EDITOR Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set. MAIL Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is present in the env_keep list). HOME Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the env_keep list. LOGNAME Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list). PATH May be overridden by the security policy. SHELL Used to determine shell to run with -s option. SUDO_ASKPASS Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified. SUDO_COMMAND Set to the command run by sudo, including any args. The args are truncated at 4096 characters to prevent a potential execution error. SUDO_EDITOR Default editor to use in -e (sudoedit) mode. SUDO_GID Set to the group-ID of the user who invoked sudo. SUDO_PROMPT Used as the default password prompt unless the -p option was specified. SUDO_PS1 If set, PS1 will be set to its value for the program being run. SUDO_UID Set to the user-ID of the user who invoked sudo. SUDO_USER Set to the login name of the user who invoked sudo. USER Set to the same value as LOGNAME, described above. VISUAL Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set. FILES top /etc/sudo.conf front-end configuration EXAMPLES top The following examples assume a properly configured security policy. To get a file listing of an unreadable directory: $ sudo ls /usr/local/protected To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root: $ sudo -u yaz ls ~yaz To edit the index.html file as user www: $ sudoedit -u www ~www/htdocs/index.html To view system logs only accessible to root and users in the adm group: $ sudo -g adm more /var/log/syslog To run an editor as jim with a different primary group: $ sudoedit -u jim -g audio ~jim/sound.txt To shut down a machine: $ sudo shutdown -r +15 "quick reboot" To make a usage listing of the directories in the /home partition. The commands are run in a sub-shell to allow the cd command and file redirection to work. $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" DIAGNOSTICS top Error messages produced by include: editing files in a writable directory is not permitted By default, sudoedit does not permit editing a file when any of the parent directories are writable by the invoking user. This avoids a race condition that could allow the user to overwrite an arbitrary file. See the sudoedit_checkdir option in sudoers(5) for more information. editing symbolic links is not permitted By default, sudoedit does not follow symbolic links when opening files. See the sudoedit_follow option in sudoers(5) for more information. effective uid is not 0, is sudo installed setuid root? was not run with root privileges. The binary must be owned by the root user and have the set-user-ID bit set. Also, it must not be located on a file system mounted with the nosuid option or on an NFS file system that maps uid 0 to an unprivileged uid. effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges? was not run with root privileges. The binary has the proper owner and permissions but it still did not run with root privileges. The most common reason for this is that the file system the binary is located on is mounted with the nosuid option or it is an NFS file system that maps uid 0 to an unprivileged uid. fatal error, unable to load plugins An error occurred while loading or initializing the plugins specified in sudo.conf(5). invalid environment variable name One or more environment variable names specified via the -E option contained an equal sign (=). The arguments to the -E option should be environment variable names without an associated value. no password was provided When tried to read the password, it did not receive any characters. This may happen if no terminal is available (or the -S option is specified) and the standard input has been redirected from /dev/null. a terminal is required to read the password needs to read the password but there is no mechanism available for it to do so. A terminal is not present to read the password from, has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the sudo.conf(5) file or the SUDO_ASKPASS environment variable. no writable temporary directory found sudoedit was unable to find a usable temporary directory in which to store its intermediate files. The no new privileges flag is set, which prevents sudo from running as root. was run by a process that has the Linux no new privileges flag is set. This causes the set-user-ID bit to be ignored when running an executable, which will prevent from functioning. The most likely cause for this is running within a container that sets this flag. Check the documentation to see if it is possible to configure the container such that the flag is not set. sudo must be owned by uid 0 and have the setuid bit set was not run with root privileges. The binary does not have the correct owner or permissions. It must be owned by the root user and have the set-user-ID bit set. sudoedit is not supported on this platform It is only possible to run sudoedit on systems that support setting the effective user-ID. timed out reading password The user did not enter a password before the password timeout (5 minutes by default) expired. you do not exist in the passwd database Your user-ID does not appear in the system passwd database. you may not specify environment variables in edit mode It is only possible to specify environment variables when running a command. When editing a file, the editor is run with the user's environment unmodified. SEE ALSO top su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8) HISTORY top See the HISTORY.md file in the distribution (https://www.sudo.ws/about/history/) for a brief history of sudo. AUTHORS top Many people have worked on over the years; this version consists of code written primarily by: Todd C. Miller See the CONTRIBUTORS.md file in the distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed to . CAVEATS top There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via . Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with the sudoers(5) plugin's noexec functionality. It is not meaningful to run the cd command directly via sudo, e.g., $ sudo cd /usr/local/protected since when the command exits the parent process (your shell) will still be the same. The -D option can be used to run a command in a specific directory. Running shell scripts via can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, set-user-ID shell scripts are generally safe). BUGS top If you believe you have found a bug in , you can submit a bug report at https://bugzilla.sudo.ws/ SUPPORT top Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives. DISCLAIMER top is provided AS IS and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE.md file distributed with or https://www.sudo.ws/about/license/ for complete details. COLOPHON top This page is part of the sudo (execute a command as another user) project. Information about the project can be found at https://www.sudo.ws/. If you have a bug report for this manual page, see https://bugzilla.sudo.ws/. This page was obtained from the project's upstream Git repository https://github.com/sudo-project/sudo on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Sudo 1.9.15p4 August 9, 2023 SUDO(8) Pages that refer to this page: homectl(1), journalctl(1), localectl(1), loginctl(1), machinectl(1), portablectl(1), setpriv(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), uid0(1), userdbctl(1), nsswitch.conf(5), credentials(7), systemd-tmpfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of "/var/www/html/mysite/tmp_file_upload/" to "nobody" Bash Command:<START>sudo chown nobody /var/www/html/mysite/tmp_file_upload/<END>

Change the owner of "destination_dir" to "user"

chown user destination_dir

['chown']

Output a Bash command to accomplish the following task. Task: Change the owner of "destination_dir" to "user" Bash Command:<START>chown user destination_dir<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner of "destination_dir" to "user" Bash Command:<START>chown user destination_dir<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of "destination_dir" to "user" Bash Command:<START>chown user destination_dir<END>

Change the owner of "process" to "root"

sudo chown root process

['chown', 'sudo']

Output a Bash command to accomplish the following task. Task: Change the owner of "process" to "root" Bash Command:<START>sudo chown root process<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n # sudo\n\n> Executes a single command as the superuser or another user.\n> More information: <https://www.sudo.ws/sudo.html>.\n\n- Run a command as the superuser:\n\n`sudo {{less /var/log/syslog}}`\n\n- Edit a file as the superuser with your default editor:\n\n`sudo --edit {{/etc/fstab}}`\n\n- Run a command as another user and/or group:\n\n`sudo --user={{user}} --group={{group}} {{id -a}}`\n\n- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):\n\n`sudo !!`\n\n- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login`\n\n- Launch the default shell with superuser privileges without changing the environment:\n\n`sudo --shell`\n\n- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login --user={{user}}`\n\n- List the allowed (and forbidden) commands for the invoking user:\n\n`sudo --list`\n Task: Change the owner of "process" to "root" Bash Command:<START>sudo chown root process<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sudo(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sudo(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON SUDO(8) System Manager's Manual SUDO(8) NAME top sudo, sudoedit execute a command as another user SYNOPSIS top sudo -h | -K | -k | -V sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command [arg ...]] sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] [VAR=value] [-i | -s] [command [arg ...]] sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] file ... DESCRIPTION top allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy. supports a plugin architecture for security policies, auditing, and input/output logging. Third parties can develop and distribute their own plugins to work seamlessly with the front- end. The default security policy is sudoers, which is configured via the file /etc/sudoers, or via LDAP. See the Plugins section for more information. The security policy determines what privileges, if any, a user has to run . The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific; the default password prompt timeout for the sudoers security policy is 5 minutes. Security policies may support credential caching to allow the user to run again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running with the -v option, a user can update the cached credentials without running a command. On systems where is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced. When invoked as sudoedit, the -e option (described below), is implied. Security policies and audit plugins may log successful and failed attempts to run . If an I/O plugin is configured, the running command's input and output may be logged as well. The options are as follows: -A, --askpass Normally, if requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example: # Path to askpass helper program Path askpass /usr/X11R6/bin/ssh-askpass If no askpass program is available, will exit with an error. -B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used. -b, --background Run the given command in the background. It is not possible to use shell job control to manipulate background processes started by . Most interactive commands will fail to work properly in background mode. -C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, will close all open file descriptors other than standard input, standard output, and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option. -D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory. -E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment. --preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times. -e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken: 1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used. 3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy: Symbolic links may not be edited (version 1.8.15 and higher). Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher). Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher). Users are never allowed to edit device special files. If the specified file does not exist, it will be created. Unlike most commands run by sudo, the editor is run with the invoking user's environment unmodified. If the temporary file becomes empty after editing, the user will be prompted before it is installed. If, for some reason, is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file. -g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the # character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the # be escaped with a backslash (\). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use. -H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior. -h, --help Display a short help message to the standard output and exit. -h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. The sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host. -i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login- specific resource files such as .profile, .bash_profile, or .login will be read by the shell. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use. -K, --remove-timestamp Similar to the -k option, except that it removes every cached credential for the user, regardless of the terminal or parent process ID. The next time is run, a password must be entered if the security policy requires authentication. It is not possible to use the -K option in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching. -k, --reset-timestamp When used without a command, invalidates the user's cached credentials for the current session. The next time is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with commands run in a different terminal session. See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke permissions from a .logout file. When used in conjunction with a command or an option that may require a password, this option will cause to ignore the user's cached credentials. As a result, will prompt for a password (if one is required by the security policy) and will not update the user's cached credentials. Not all security policies support credential caching. -l, --list If no command is specified, list the privileges for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format. If a command is specified and is permitted by the security policy for the invoking user (or the, user specified by the -U option) on the current host, the fully-qualified path to the command is displayed along with any args. If -l is specified more than once (and the security policy supports it), the matching rule is displayed in a verbose format along with the command. If a command is specified but not allowed by the policy, will exit with a status value of 1. -N, --no-update Do not update the user's cached credentials, even if the user successfully authenticates. Unlike the -k flag, existing cached credentials are used if they are valid. To detect when the user's cached credentials are valid (or when no authentication is required), the following can be used: sudo -Nnv Not all security policies support credential caching. -n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, will display an error message and exit. -P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user. -p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent (%) escape sequences are supported by the sudoers policy: %H expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in sudoers(5)) %h expanded to the local host name without the domain name %p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5)) %U expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified) %u expanded to the invoking user's login name %% two consecutive % characters are collapsed into a single % character The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers. -R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory. -S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device. -s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. -U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. When using the sudoers policy, the -U option is restricted to the root user and users with either the list priviege for the specified user or the ability to run any command as root or user on the current host. -T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the user's ability to set timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled. -u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the # character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the # be escaped with a backslash (\). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this. -V, --version Print the version string as well as the version string of any configured plugins. If the invoking user is already root, the -V option will display the options passed to configure when was built; plugins may display additional information such as default options. -v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials. -- The -- is used to delimit the end of the options. Subsequent options are passed to the command. Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input. Environment variables to be set for the command may also be passed as options to in the form VAR=value, for example LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be subject to restrictions imposed by the security policy plugin. The sudoers policy subjects environment variables passed as options to the same restrictions as existing environment variables with one important difference. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information. COMMAND EXECUTION top When executes a command, the security policy specifies the execution environment for the command. Typically, the real and effective user and group and IDs are set to match those of the target user, as specified in the password database, and the group vector is initialized based on the group database (unless the -P option was specified). The following parameters may be specified by security policy: real and effective user-ID real and effective group-ID supplementary group-IDs the environment list current working directory file creation mode mask (umask) scheduling priority (aka nice value) Process model There are two distinct ways can run a command. If an I/O logging plugin is configured to log terminal I/O, or if the security policy explicitly requests it, a new pseudo-terminal (pty) is allocated and fork(2) is used to create a second process, referred to as the monitor. The monitor creates a new terminal session with itself as the leader and the pty as its controlling terminal, calls fork(2) again, sets up the execution environment as described above, and then uses the execve(2) system call to run the command in the child process. The monitor exists to relay job control signals between the user's terminal and the pty the command is being run in. This makes it possible to suspend and resume the command normally. Without the monitor, the command would be in what POSIX terms an orphaned process group and it would not receive any job control signals from the kernel. When the command exits or is terminated by a signal, the monitor passes the command's exit status to the main process and exits. After receiving the command's exit status, the main process passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugin, and exits. This mode is the default for sudo versions 1.9.14 and above when using the sudoers policy. If no pty is used, calls fork(2), sets up the execution environment as described above, and uses the execve(2) system call to run the command in the child process. The main process waits until the command has completed, then passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugins, and exits. As a special case, if the policy plugin does not define a close function, will execute the command directly instead of calling fork(2) first. The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled. Both pam_session and pam_setcred are enabled by default on systems using PAM. This mode is the default for sudo versions prior to 1.9.14 when using the sudoers policy. On systems that use PAM, the security policy's close function is responsible for closing the PAM session. It may also log the command's exit status. Signal handling When the command is run as a child of the process, will relay signals it receives to the command. The SIGINT and SIGQUIT signals are only relayed when the command is being run in a new pty or when the signal was sent by a user process, not the kernel. This prevents the command from receiving SIGINT twice each time the user enters control-C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by . As a special case, will not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) utility sends SIGTERM to all non-system processes other than itself before rebooting the system. This prevents from relaying the SIGTERM signal it received back to reboot(8), which might then exit before the system was actually rebooted, leaving it in a half-dead state similar to single user mode. Note, however, that this check only applies to the command run by and not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via may cause the system to end up in this undefined state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the command and the calling process). Plugins Plugins may be specified via Plugin directives in the sudo.conf(5) file. They may be loaded as dynamic shared objects (on systems that support them), or compiled directly into the binary. If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, will use sudoers(5) for the policy, auditing, and I/O logging plugins. See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for more information about the plugin architecture. EXIT VALUE top Upon successful execution of a command, the exit status from will be the exit status of the program that was executed. If the command terminated due to receipt of a signal, will send itself the same signal that terminated the command. If the -l option was specified without a command, will exit with a value of 0 if the user is allowed to run and they authenticated successfully (as required by the security policy). If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by the security policy, otherwise it will be 1. If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, exits with a value of 1. In the latter case, the error string is printed to the standard error. If cannot stat(2) one or more entries in the user's PATH, an error is printed to the standard error. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat(2) to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. SECURITY NOTES top tries to be safe when executing external commands. To prevent command spoofing, checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the program that executes. Users should never be granted privileges to execute files that are writable by the user or that reside in a directory that is writable by the user. If the user can modify or replace the command there is no way to limit what additional commands they can run. By default, will only log the command it explicitly runs. If a user runs a command such as sudo su or sudo sh, subsequent commands run from that shell are not subject to sudo's security policy. The same is true for commands that offer shell escapes (including most editors). If I/O logging is enabled, subsequent commands will have their input and/or output logged, but there will not be traditional logs for those commands. Because of this, care must be taken when giving users access to commands via to verify that the command does not inadvertently give the user an effective root shell. For information on ways to address this, see the Preventing shell escapes section in sudoers(5). To prevent the disclosure of potentially sensitive information, disables core dumps by default while it is executing (they are re-enabled for the command that is run). This historical practice dates from a time when most operating systems allowed set-user-ID processes to dump core by default. To aid in debugging crashes, you may wish to re-enable core dumps by setting disable_coredump to false in the sudo.conf(5) file as follows: Set disable_coredump false See the sudo.conf(5) manual for more information. ENVIRONMENT top utilizes the following environment variables. The security policy has control over the actual content of the command's environment. EDITOR Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set. MAIL Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is present in the env_keep list). HOME Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the env_keep list. LOGNAME Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list). PATH May be overridden by the security policy. SHELL Used to determine shell to run with -s option. SUDO_ASKPASS Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified. SUDO_COMMAND Set to the command run by sudo, including any args. The args are truncated at 4096 characters to prevent a potential execution error. SUDO_EDITOR Default editor to use in -e (sudoedit) mode. SUDO_GID Set to the group-ID of the user who invoked sudo. SUDO_PROMPT Used as the default password prompt unless the -p option was specified. SUDO_PS1 If set, PS1 will be set to its value for the program being run. SUDO_UID Set to the user-ID of the user who invoked sudo. SUDO_USER Set to the login name of the user who invoked sudo. USER Set to the same value as LOGNAME, described above. VISUAL Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set. FILES top /etc/sudo.conf front-end configuration EXAMPLES top The following examples assume a properly configured security policy. To get a file listing of an unreadable directory: $ sudo ls /usr/local/protected To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root: $ sudo -u yaz ls ~yaz To edit the index.html file as user www: $ sudoedit -u www ~www/htdocs/index.html To view system logs only accessible to root and users in the adm group: $ sudo -g adm more /var/log/syslog To run an editor as jim with a different primary group: $ sudoedit -u jim -g audio ~jim/sound.txt To shut down a machine: $ sudo shutdown -r +15 "quick reboot" To make a usage listing of the directories in the /home partition. The commands are run in a sub-shell to allow the cd command and file redirection to work. $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" DIAGNOSTICS top Error messages produced by include: editing files in a writable directory is not permitted By default, sudoedit does not permit editing a file when any of the parent directories are writable by the invoking user. This avoids a race condition that could allow the user to overwrite an arbitrary file. See the sudoedit_checkdir option in sudoers(5) for more information. editing symbolic links is not permitted By default, sudoedit does not follow symbolic links when opening files. See the sudoedit_follow option in sudoers(5) for more information. effective uid is not 0, is sudo installed setuid root? was not run with root privileges. The binary must be owned by the root user and have the set-user-ID bit set. Also, it must not be located on a file system mounted with the nosuid option or on an NFS file system that maps uid 0 to an unprivileged uid. effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges? was not run with root privileges. The binary has the proper owner and permissions but it still did not run with root privileges. The most common reason for this is that the file system the binary is located on is mounted with the nosuid option or it is an NFS file system that maps uid 0 to an unprivileged uid. fatal error, unable to load plugins An error occurred while loading or initializing the plugins specified in sudo.conf(5). invalid environment variable name One or more environment variable names specified via the -E option contained an equal sign (=). The arguments to the -E option should be environment variable names without an associated value. no password was provided When tried to read the password, it did not receive any characters. This may happen if no terminal is available (or the -S option is specified) and the standard input has been redirected from /dev/null. a terminal is required to read the password needs to read the password but there is no mechanism available for it to do so. A terminal is not present to read the password from, has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the sudo.conf(5) file or the SUDO_ASKPASS environment variable. no writable temporary directory found sudoedit was unable to find a usable temporary directory in which to store its intermediate files. The no new privileges flag is set, which prevents sudo from running as root. was run by a process that has the Linux no new privileges flag is set. This causes the set-user-ID bit to be ignored when running an executable, which will prevent from functioning. The most likely cause for this is running within a container that sets this flag. Check the documentation to see if it is possible to configure the container such that the flag is not set. sudo must be owned by uid 0 and have the setuid bit set was not run with root privileges. The binary does not have the correct owner or permissions. It must be owned by the root user and have the set-user-ID bit set. sudoedit is not supported on this platform It is only possible to run sudoedit on systems that support setting the effective user-ID. timed out reading password The user did not enter a password before the password timeout (5 minutes by default) expired. you do not exist in the passwd database Your user-ID does not appear in the system passwd database. you may not specify environment variables in edit mode It is only possible to specify environment variables when running a command. When editing a file, the editor is run with the user's environment unmodified. SEE ALSO top su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8) HISTORY top See the HISTORY.md file in the distribution (https://www.sudo.ws/about/history/) for a brief history of sudo. AUTHORS top Many people have worked on over the years; this version consists of code written primarily by: Todd C. Miller See the CONTRIBUTORS.md file in the distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed to . CAVEATS top There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via . Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with the sudoers(5) plugin's noexec functionality. It is not meaningful to run the cd command directly via sudo, e.g., $ sudo cd /usr/local/protected since when the command exits the parent process (your shell) will still be the same. The -D option can be used to run a command in a specific directory. Running shell scripts via can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, set-user-ID shell scripts are generally safe). BUGS top If you believe you have found a bug in , you can submit a bug report at https://bugzilla.sudo.ws/ SUPPORT top Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives. DISCLAIMER top is provided AS IS and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE.md file distributed with or https://www.sudo.ws/about/license/ for complete details. COLOPHON top This page is part of the sudo (execute a command as another user) project. Information about the project can be found at https://www.sudo.ws/. If you have a bug report for this manual page, see https://bugzilla.sudo.ws/. This page was obtained from the project's upstream Git repository https://github.com/sudo-project/sudo on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Sudo 1.9.15p4 August 9, 2023 SUDO(8) Pages that refer to this page: homectl(1), journalctl(1), localectl(1), loginctl(1), machinectl(1), portablectl(1), setpriv(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), uid0(1), userdbctl(1), nsswitch.conf(5), credentials(7), systemd-tmpfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of "process" to "root" Bash Command:<START>sudo chown root process<END>

Change the owner of all ".txt" files in directory tree "/mydir" to "root"

find /mydir -type f -name "*.txt" -execdir chown root {} ';'

['find', 'chown']

Output a Bash command to accomplish the following task. Task: Change the owner of all ".txt" files in directory tree "/mydir" to "root" Bash Command:<START>find /mydir -type f -name "*.txt" -execdir chown root {} ';'<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner of all ".txt" files in directory tree "/mydir" to "root" Bash Command:<START>find /mydir -type f -name "*.txt" -execdir chown root {} ';'<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of all ".txt" files in directory tree "/mydir" to "root" Bash Command:<START>find /mydir -type f -name "*.txt" -execdir chown root {} ';'<END>

Change the owner of all files in "/empty_dir/" to "root" using at most 10 files at a time

ls /empty_dir/ | xargs -L10 chown root

['ls', 'xargs', 'chown']

Output a Bash command to accomplish the following task. Task: Change the owner of all files in "/empty_dir/" to "root" using at most 10 files at a time Bash Command:<START>ls /empty_dir/ | xargs -L10 chown root<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # ls\n\n> List directory contents.\n> More information: <https://www.gnu.org/software/coreutils/ls>.\n\n- List files one per line:\n\n`ls -1`\n\n- List all files, including hidden files:\n\n`ls -a`\n\n- List all files, with trailing `/` added to directory names:\n\n`ls -F`\n\n- Long format list (permissions, ownership, size, and modification date) of all files:\n\n`ls -la`\n\n- Long format list with size displayed using human-readable units (KiB, MiB, GiB):\n\n`ls -lh`\n\n- Long format list sorted by size (descending) recursively:\n\n`ls -lSR`\n\n- Long format list of all files, sorted by modification date (oldest first):\n\n`ls -ltr`\n\n- Only list directories:\n\n`ls -d */`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner of all files in "/empty_dir/" to "root" using at most 10 files at a time Bash Command:<START>ls /empty_dir/ | xargs -L10 chown root<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: ls(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training ls(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON LS(1) User Commands LS(1) NAME top ls - list directory contents SYNOPSIS top ls [OPTION]... [FILE]... DESCRIPTION top List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort is specified. Mandatory arguments to long options are mandatory for short options too. -a, --all do not ignore entries starting with . -A, --almost-all do not list implied . and .. --author with -l, print the author of each file -b, --escape print C-style escapes for nongraphic characters --block-size=SIZE with -l, scale sizes by SIZE when printing them; e.g., '--block-size=M'; see SIZE format below -B, --ignore-backups do not list implied entries ending with ~ -c with -lt: sort by, and show, ctime (time of last change of file status information); with -l: show ctime and sort by name; otherwise: sort by ctime, newest first -C list entries by columns --color[=WHEN] color the output WHEN; more info below -d, --directory list directories themselves, not their contents -D, --dired generate output designed for Emacs' dired mode -f list all entries in directory order -F, --classify[=WHEN] append indicator (one of */=>@|) to entries WHEN --file-type likewise, except do not append '*' --format=WORD across -x, commas -m, horizontal -x, long -l, single-column -1, verbose -l, vertical -C --full-time like -l --time-style=full-iso -g like -l, but do not list owner --group-directories-first group directories before files; can be augmented with a --sort option, but any use of --sort=none (-U) disables grouping -G, --no-group in a long listing, don't print group names -h, --human-readable with -l and -s, print sizes like 1K 234M 2G etc. --si likewise, but use powers of 1000 not 1024 -H, --dereference-command-line follow symbolic links listed on the command line --dereference-command-line-symlink-to-dir follow each command line symbolic link that points to a directory --hide=PATTERN do not list implied entries matching shell PATTERN (overridden by -a or -A) --hyperlink[=WHEN] hyperlink file names WHEN --indicator-style=WORD append indicator with style WORD to entry names: none (default), slash (-p), file-type (--file-type), classify (-F) -i, --inode print the index number of each file -I, --ignore=PATTERN do not list implied entries matching shell PATTERN -k, --kibibytes default to 1024-byte blocks for file system usage; used only with -s and per directory totals -l use a long listing format -L, --dereference when showing file information for a symbolic link, show information for the file the link references rather than for the link itself -m fill width with a comma separated list of entries -n, --numeric-uid-gid like -l, but list numeric user and group IDs -N, --literal print entry names without quoting -o like -l, but do not list group information -p, --indicator-style=slash append / indicator to directories -q, --hide-control-chars print ? instead of nongraphic characters --show-control-chars show nongraphic characters as-is (the default, unless program is 'ls' and output is a terminal) -Q, --quote-name enclose entry names in double quotes --quoting-style=WORD use quoting style WORD for entry names: literal, locale, shell, shell-always, shell-escape, shell-escape-always, c, escape (overrides QUOTING_STYLE environment variable) -r, --reverse reverse order while sorting -R, --recursive list subdirectories recursively -s, --size print the allocated size of each file, in blocks -S sort by file size, largest first --sort=WORD sort by WORD instead of name: none (-U), size (-S), time (-t), version (-v), extension (-X), width --time=WORD select which timestamp used to display or sort; access time (-u): atime, access, use; metadata change time (-c): ctime, status; modified time (default): mtime, modification; birth time: birth, creation; with -l, WORD determines which time to show; with --sort=time, sort by WORD (newest first) --time-style=TIME_STYLE time/date format with -l; see TIME_STYLE below -t sort by time, newest first; see --time -T, --tabsize=COLS assume tab stops at each COLS instead of 8 -u with -lt: sort by, and show, access time; with -l: show access time and sort by name; otherwise: sort by access time, newest first -U do not sort; list entries in directory order -v natural sort of (version) numbers within text -w, --width=COLS set output width to COLS. 0 means no limit -x list entries by lines instead of by columns -X sort alphabetically by entry extension -Z, --context print any security context of each file --zero end each output line with NUL, not newline -1 list one file per line --help display this help and exit --version output version information and exit The SIZE argument is an integer and optional unit (example: 10K is 10*1024). Units are K,M,G,T,P,E,Z,Y,R,Q (powers of 1024) or KB,MB,... (powers of 1000). Binary prefixes can be used, too: KiB=K, MiB=M, and so on. The TIME_STYLE argument can be full-iso, long-iso, iso, locale, or +FORMAT. FORMAT is interpreted like in date(1). If FORMAT is FORMAT1<newline>FORMAT2, then FORMAT1 applies to non-recent files and FORMAT2 to recent files. TIME_STYLE prefixed with 'posix-' takes effect only outside the POSIX locale. Also the TIME_STYLE environment variable sets the default style to use. The WHEN argument defaults to 'always' and can also be 'auto' or 'never'. Using color to distinguish file types is disabled both by default and with --color=never. With --color=auto, ls emits color codes only when standard output is connected to a terminal. The LS_COLORS environment variable can change the settings. Use the dircolors(1) command to set it. Exit status: 0 if OK, 1 if minor problems (e.g., cannot access subdirectory), 2 if serious trouble (e.g., cannot access command-line argument). AUTHOR top Written by Richard M. Stallman and David MacKenzie. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top dircolors(1) Full documentation <https://www.gnu.org/software/coreutils/ls> or available locally via: info '(coreutils) ls invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 LS(1) Pages that refer to this page: column(1), find(1), namei(1), stat(2), statx(2), glob(3), strverscmp(3), core(5), dir_colors(5), passwd(5), proc(5), mq_overview(7), symlink(7), lsblk(8), lsof(8), setfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of all files in "/empty_dir/" to "root" using at most 10 files at a time Bash Command:<START>ls /empty_dir/ | xargs -L10 chown root<END>

Change the owner of all files in "/empty_dir/" to "root" using at most 10 files at a time

ls /empty_dir/ | xargs -n10 chown root

['ls', 'xargs', 'chown']

Output a Bash command to accomplish the following task. Task: Change the owner of all files in "/empty_dir/" to "root" using at most 10 files at a time Bash Command:<START>ls /empty_dir/ | xargs -n10 chown root<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # ls\n\n> List directory contents.\n> More information: <https://www.gnu.org/software/coreutils/ls>.\n\n- List files one per line:\n\n`ls -1`\n\n- List all files, including hidden files:\n\n`ls -a`\n\n- List all files, with trailing `/` added to directory names:\n\n`ls -F`\n\n- Long format list (permissions, ownership, size, and modification date) of all files:\n\n`ls -la`\n\n- Long format list with size displayed using human-readable units (KiB, MiB, GiB):\n\n`ls -lh`\n\n- Long format list sorted by size (descending) recursively:\n\n`ls -lSR`\n\n- Long format list of all files, sorted by modification date (oldest first):\n\n`ls -ltr`\n\n- Only list directories:\n\n`ls -d */`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner of all files in "/empty_dir/" to "root" using at most 10 files at a time Bash Command:<START>ls /empty_dir/ | xargs -n10 chown root<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: ls(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training ls(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON LS(1) User Commands LS(1) NAME top ls - list directory contents SYNOPSIS top ls [OPTION]... [FILE]... DESCRIPTION top List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort is specified. Mandatory arguments to long options are mandatory for short options too. -a, --all do not ignore entries starting with . -A, --almost-all do not list implied . and .. --author with -l, print the author of each file -b, --escape print C-style escapes for nongraphic characters --block-size=SIZE with -l, scale sizes by SIZE when printing them; e.g., '--block-size=M'; see SIZE format below -B, --ignore-backups do not list implied entries ending with ~ -c with -lt: sort by, and show, ctime (time of last change of file status information); with -l: show ctime and sort by name; otherwise: sort by ctime, newest first -C list entries by columns --color[=WHEN] color the output WHEN; more info below -d, --directory list directories themselves, not their contents -D, --dired generate output designed for Emacs' dired mode -f list all entries in directory order -F, --classify[=WHEN] append indicator (one of */=>@|) to entries WHEN --file-type likewise, except do not append '*' --format=WORD across -x, commas -m, horizontal -x, long -l, single-column -1, verbose -l, vertical -C --full-time like -l --time-style=full-iso -g like -l, but do not list owner --group-directories-first group directories before files; can be augmented with a --sort option, but any use of --sort=none (-U) disables grouping -G, --no-group in a long listing, don't print group names -h, --human-readable with -l and -s, print sizes like 1K 234M 2G etc. --si likewise, but use powers of 1000 not 1024 -H, --dereference-command-line follow symbolic links listed on the command line --dereference-command-line-symlink-to-dir follow each command line symbolic link that points to a directory --hide=PATTERN do not list implied entries matching shell PATTERN (overridden by -a or -A) --hyperlink[=WHEN] hyperlink file names WHEN --indicator-style=WORD append indicator with style WORD to entry names: none (default), slash (-p), file-type (--file-type), classify (-F) -i, --inode print the index number of each file -I, --ignore=PATTERN do not list implied entries matching shell PATTERN -k, --kibibytes default to 1024-byte blocks for file system usage; used only with -s and per directory totals -l use a long listing format -L, --dereference when showing file information for a symbolic link, show information for the file the link references rather than for the link itself -m fill width with a comma separated list of entries -n, --numeric-uid-gid like -l, but list numeric user and group IDs -N, --literal print entry names without quoting -o like -l, but do not list group information -p, --indicator-style=slash append / indicator to directories -q, --hide-control-chars print ? instead of nongraphic characters --show-control-chars show nongraphic characters as-is (the default, unless program is 'ls' and output is a terminal) -Q, --quote-name enclose entry names in double quotes --quoting-style=WORD use quoting style WORD for entry names: literal, locale, shell, shell-always, shell-escape, shell-escape-always, c, escape (overrides QUOTING_STYLE environment variable) -r, --reverse reverse order while sorting -R, --recursive list subdirectories recursively -s, --size print the allocated size of each file, in blocks -S sort by file size, largest first --sort=WORD sort by WORD instead of name: none (-U), size (-S), time (-t), version (-v), extension (-X), width --time=WORD select which timestamp used to display or sort; access time (-u): atime, access, use; metadata change time (-c): ctime, status; modified time (default): mtime, modification; birth time: birth, creation; with -l, WORD determines which time to show; with --sort=time, sort by WORD (newest first) --time-style=TIME_STYLE time/date format with -l; see TIME_STYLE below -t sort by time, newest first; see --time -T, --tabsize=COLS assume tab stops at each COLS instead of 8 -u with -lt: sort by, and show, access time; with -l: show access time and sort by name; otherwise: sort by access time, newest first -U do not sort; list entries in directory order -v natural sort of (version) numbers within text -w, --width=COLS set output width to COLS. 0 means no limit -x list entries by lines instead of by columns -X sort alphabetically by entry extension -Z, --context print any security context of each file --zero end each output line with NUL, not newline -1 list one file per line --help display this help and exit --version output version information and exit The SIZE argument is an integer and optional unit (example: 10K is 10*1024). Units are K,M,G,T,P,E,Z,Y,R,Q (powers of 1024) or KB,MB,... (powers of 1000). Binary prefixes can be used, too: KiB=K, MiB=M, and so on. The TIME_STYLE argument can be full-iso, long-iso, iso, locale, or +FORMAT. FORMAT is interpreted like in date(1). If FORMAT is FORMAT1<newline>FORMAT2, then FORMAT1 applies to non-recent files and FORMAT2 to recent files. TIME_STYLE prefixed with 'posix-' takes effect only outside the POSIX locale. Also the TIME_STYLE environment variable sets the default style to use. The WHEN argument defaults to 'always' and can also be 'auto' or 'never'. Using color to distinguish file types is disabled both by default and with --color=never. With --color=auto, ls emits color codes only when standard output is connected to a terminal. The LS_COLORS environment variable can change the settings. Use the dircolors(1) command to set it. Exit status: 0 if OK, 1 if minor problems (e.g., cannot access subdirectory), 2 if serious trouble (e.g., cannot access command-line argument). AUTHOR top Written by Richard M. Stallman and David MacKenzie. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top dircolors(1) Full documentation <https://www.gnu.org/software/coreutils/ls> or available locally via: info '(coreutils) ls invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 LS(1) Pages that refer to this page: column(1), find(1), namei(1), stat(2), statx(2), glob(3), strverscmp(3), core(5), dir_colors(5), passwd(5), proc(5), mq_overview(7), symlink(7), lsblk(8), lsof(8), setfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of all files in "/empty_dir/" to "root" using at most 10 files at a time Bash Command:<START>ls /empty_dir/ | xargs -n10 chown root<END>

Change the owner of all files in the current directory tree excluding those who match "./var/foo*" to "www-data"

find . -not -iwholename './var/foo*' -exec chown www-data '{}' \;

['find', 'chown']

Output a Bash command to accomplish the following task. Task: Change the owner of all files in the current directory tree excluding those who match "./var/foo*" to "www-data" Bash Command:<START>find . -not -iwholename './var/foo*' -exec chown www-data '{}' \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner of all files in the current directory tree excluding those who match "./var/foo*" to "www-data" Bash Command:<START>find . -not -iwholename './var/foo*' -exec chown www-data '{}' \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of all files in the current directory tree excluding those who match "./var/foo*" to "www-data" Bash Command:<START>find . -not -iwholename './var/foo*' -exec chown www-data '{}' \;<END>

Change the owner of all files in the directory tree "dir_to_start" excluding directory "dir_to_exclude" to "owner"

find dir_to_start -name dir_to_exclude -prune -o -print0 | xargs -0 chown owner

['find', 'xargs', 'chown']

Output a Bash command to accomplish the following task. Task: Change the owner of all files in the directory tree "dir_to_start" excluding directory "dir_to_exclude" to "owner" Bash Command:<START>find dir_to_start -name dir_to_exclude -prune -o -print0 | xargs -0 chown owner<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner of all files in the directory tree "dir_to_start" excluding directory "dir_to_exclude" to "owner" Bash Command:<START>find dir_to_start -name dir_to_exclude -prune -o -print0 | xargs -0 chown owner<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of all files in the directory tree "dir_to_start" excluding directory "dir_to_exclude" to "owner" Bash Command:<START>find dir_to_start -name dir_to_exclude -prune -o -print0 | xargs -0 chown owner<END>

Change the owner of all files in the directory tree "dir_to_start" excluding file "file_to_exclude" to "owner"

find dir_to_start -not -name "file_to_exclude" -print0 | xargs -0 chown owner

['find', 'xargs', 'chown']

Output a Bash command to accomplish the following task. Task: Change the owner of all files in the directory tree "dir_to_start" excluding file "file_to_exclude" to "owner" Bash Command:<START>find dir_to_start -not -name "file_to_exclude" -print0 | xargs -0 chown owner<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner of all files in the directory tree "dir_to_start" excluding file "file_to_exclude" to "owner" Bash Command:<START>find dir_to_start -not -name "file_to_exclude" -print0 | xargs -0 chown owner<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner of all files in the directory tree "dir_to_start" excluding file "file_to_exclude" to "owner" Bash Command:<START>find dir_to_start -not -name "file_to_exclude" -print0 | xargs -0 chown owner<END>

Change the owner to "hduser" and group to "hadoop" of "{directory path}"

sudo chown hduser:hadoop {directory path}

['chown', 'sudo']

Output a Bash command to accomplish the following task. Task: Change the owner to "hduser" and group to "hadoop" of "{directory path}" Bash Command:<START>sudo chown hduser:hadoop {directory path}<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n # sudo\n\n> Executes a single command as the superuser or another user.\n> More information: <https://www.sudo.ws/sudo.html>.\n\n- Run a command as the superuser:\n\n`sudo {{less /var/log/syslog}}`\n\n- Edit a file as the superuser with your default editor:\n\n`sudo --edit {{/etc/fstab}}`\n\n- Run a command as another user and/or group:\n\n`sudo --user={{user}} --group={{group}} {{id -a}}`\n\n- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):\n\n`sudo !!`\n\n- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login`\n\n- Launch the default shell with superuser privileges without changing the environment:\n\n`sudo --shell`\n\n- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login --user={{user}}`\n\n- List the allowed (and forbidden) commands for the invoking user:\n\n`sudo --list`\n Task: Change the owner to "hduser" and group to "hadoop" of "{directory path}" Bash Command:<START>sudo chown hduser:hadoop {directory path}<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sudo(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sudo(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON SUDO(8) System Manager's Manual SUDO(8) NAME top sudo, sudoedit execute a command as another user SYNOPSIS top sudo -h | -K | -k | -V sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command [arg ...]] sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] [VAR=value] [-i | -s] [command [arg ...]] sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] file ... DESCRIPTION top allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy. supports a plugin architecture for security policies, auditing, and input/output logging. Third parties can develop and distribute their own plugins to work seamlessly with the front- end. The default security policy is sudoers, which is configured via the file /etc/sudoers, or via LDAP. See the Plugins section for more information. The security policy determines what privileges, if any, a user has to run . The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific; the default password prompt timeout for the sudoers security policy is 5 minutes. Security policies may support credential caching to allow the user to run again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running with the -v option, a user can update the cached credentials without running a command. On systems where is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced. When invoked as sudoedit, the -e option (described below), is implied. Security policies and audit plugins may log successful and failed attempts to run . If an I/O plugin is configured, the running command's input and output may be logged as well. The options are as follows: -A, --askpass Normally, if requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example: # Path to askpass helper program Path askpass /usr/X11R6/bin/ssh-askpass If no askpass program is available, will exit with an error. -B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used. -b, --background Run the given command in the background. It is not possible to use shell job control to manipulate background processes started by . Most interactive commands will fail to work properly in background mode. -C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, will close all open file descriptors other than standard input, standard output, and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option. -D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory. -E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment. --preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times. -e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken: 1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used. 3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy: Symbolic links may not be edited (version 1.8.15 and higher). Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher). Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher). Users are never allowed to edit device special files. If the specified file does not exist, it will be created. Unlike most commands run by sudo, the editor is run with the invoking user's environment unmodified. If the temporary file becomes empty after editing, the user will be prompted before it is installed. If, for some reason, is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file. -g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the # character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the # be escaped with a backslash (\). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use. -H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior. -h, --help Display a short help message to the standard output and exit. -h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. The sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host. -i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login- specific resource files such as .profile, .bash_profile, or .login will be read by the shell. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use. -K, --remove-timestamp Similar to the -k option, except that it removes every cached credential for the user, regardless of the terminal or parent process ID. The next time is run, a password must be entered if the security policy requires authentication. It is not possible to use the -K option in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching. -k, --reset-timestamp When used without a command, invalidates the user's cached credentials for the current session. The next time is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with commands run in a different terminal session. See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke permissions from a .logout file. When used in conjunction with a command or an option that may require a password, this option will cause to ignore the user's cached credentials. As a result, will prompt for a password (if one is required by the security policy) and will not update the user's cached credentials. Not all security policies support credential caching. -l, --list If no command is specified, list the privileges for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format. If a command is specified and is permitted by the security policy for the invoking user (or the, user specified by the -U option) on the current host, the fully-qualified path to the command is displayed along with any args. If -l is specified more than once (and the security policy supports it), the matching rule is displayed in a verbose format along with the command. If a command is specified but not allowed by the policy, will exit with a status value of 1. -N, --no-update Do not update the user's cached credentials, even if the user successfully authenticates. Unlike the -k flag, existing cached credentials are used if they are valid. To detect when the user's cached credentials are valid (or when no authentication is required), the following can be used: sudo -Nnv Not all security policies support credential caching. -n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, will display an error message and exit. -P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user. -p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent (%) escape sequences are supported by the sudoers policy: %H expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in sudoers(5)) %h expanded to the local host name without the domain name %p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5)) %U expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified) %u expanded to the invoking user's login name %% two consecutive % characters are collapsed into a single % character The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers. -R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory. -S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device. -s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. -U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. When using the sudoers policy, the -U option is restricted to the root user and users with either the list priviege for the specified user or the ability to run any command as root or user on the current host. -T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the user's ability to set timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled. -u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the # character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the # be escaped with a backslash (\). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this. -V, --version Print the version string as well as the version string of any configured plugins. If the invoking user is already root, the -V option will display the options passed to configure when was built; plugins may display additional information such as default options. -v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials. -- The -- is used to delimit the end of the options. Subsequent options are passed to the command. Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input. Environment variables to be set for the command may also be passed as options to in the form VAR=value, for example LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be subject to restrictions imposed by the security policy plugin. The sudoers policy subjects environment variables passed as options to the same restrictions as existing environment variables with one important difference. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information. COMMAND EXECUTION top When executes a command, the security policy specifies the execution environment for the command. Typically, the real and effective user and group and IDs are set to match those of the target user, as specified in the password database, and the group vector is initialized based on the group database (unless the -P option was specified). The following parameters may be specified by security policy: real and effective user-ID real and effective group-ID supplementary group-IDs the environment list current working directory file creation mode mask (umask) scheduling priority (aka nice value) Process model There are two distinct ways can run a command. If an I/O logging plugin is configured to log terminal I/O, or if the security policy explicitly requests it, a new pseudo-terminal (pty) is allocated and fork(2) is used to create a second process, referred to as the monitor. The monitor creates a new terminal session with itself as the leader and the pty as its controlling terminal, calls fork(2) again, sets up the execution environment as described above, and then uses the execve(2) system call to run the command in the child process. The monitor exists to relay job control signals between the user's terminal and the pty the command is being run in. This makes it possible to suspend and resume the command normally. Without the monitor, the command would be in what POSIX terms an orphaned process group and it would not receive any job control signals from the kernel. When the command exits or is terminated by a signal, the monitor passes the command's exit status to the main process and exits. After receiving the command's exit status, the main process passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugin, and exits. This mode is the default for sudo versions 1.9.14 and above when using the sudoers policy. If no pty is used, calls fork(2), sets up the execution environment as described above, and uses the execve(2) system call to run the command in the child process. The main process waits until the command has completed, then passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugins, and exits. As a special case, if the policy plugin does not define a close function, will execute the command directly instead of calling fork(2) first. The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled. Both pam_session and pam_setcred are enabled by default on systems using PAM. This mode is the default for sudo versions prior to 1.9.14 when using the sudoers policy. On systems that use PAM, the security policy's close function is responsible for closing the PAM session. It may also log the command's exit status. Signal handling When the command is run as a child of the process, will relay signals it receives to the command. The SIGINT and SIGQUIT signals are only relayed when the command is being run in a new pty or when the signal was sent by a user process, not the kernel. This prevents the command from receiving SIGINT twice each time the user enters control-C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by . As a special case, will not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) utility sends SIGTERM to all non-system processes other than itself before rebooting the system. This prevents from relaying the SIGTERM signal it received back to reboot(8), which might then exit before the system was actually rebooted, leaving it in a half-dead state similar to single user mode. Note, however, that this check only applies to the command run by and not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via may cause the system to end up in this undefined state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the command and the calling process). Plugins Plugins may be specified via Plugin directives in the sudo.conf(5) file. They may be loaded as dynamic shared objects (on systems that support them), or compiled directly into the binary. If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, will use sudoers(5) for the policy, auditing, and I/O logging plugins. See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for more information about the plugin architecture. EXIT VALUE top Upon successful execution of a command, the exit status from will be the exit status of the program that was executed. If the command terminated due to receipt of a signal, will send itself the same signal that terminated the command. If the -l option was specified without a command, will exit with a value of 0 if the user is allowed to run and they authenticated successfully (as required by the security policy). If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by the security policy, otherwise it will be 1. If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, exits with a value of 1. In the latter case, the error string is printed to the standard error. If cannot stat(2) one or more entries in the user's PATH, an error is printed to the standard error. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat(2) to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. SECURITY NOTES top tries to be safe when executing external commands. To prevent command spoofing, checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the program that executes. Users should never be granted privileges to execute files that are writable by the user or that reside in a directory that is writable by the user. If the user can modify or replace the command there is no way to limit what additional commands they can run. By default, will only log the command it explicitly runs. If a user runs a command such as sudo su or sudo sh, subsequent commands run from that shell are not subject to sudo's security policy. The same is true for commands that offer shell escapes (including most editors). If I/O logging is enabled, subsequent commands will have their input and/or output logged, but there will not be traditional logs for those commands. Because of this, care must be taken when giving users access to commands via to verify that the command does not inadvertently give the user an effective root shell. For information on ways to address this, see the Preventing shell escapes section in sudoers(5). To prevent the disclosure of potentially sensitive information, disables core dumps by default while it is executing (they are re-enabled for the command that is run). This historical practice dates from a time when most operating systems allowed set-user-ID processes to dump core by default. To aid in debugging crashes, you may wish to re-enable core dumps by setting disable_coredump to false in the sudo.conf(5) file as follows: Set disable_coredump false See the sudo.conf(5) manual for more information. ENVIRONMENT top utilizes the following environment variables. The security policy has control over the actual content of the command's environment. EDITOR Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set. MAIL Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is present in the env_keep list). HOME Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the env_keep list. LOGNAME Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list). PATH May be overridden by the security policy. SHELL Used to determine shell to run with -s option. SUDO_ASKPASS Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified. SUDO_COMMAND Set to the command run by sudo, including any args. The args are truncated at 4096 characters to prevent a potential execution error. SUDO_EDITOR Default editor to use in -e (sudoedit) mode. SUDO_GID Set to the group-ID of the user who invoked sudo. SUDO_PROMPT Used as the default password prompt unless the -p option was specified. SUDO_PS1 If set, PS1 will be set to its value for the program being run. SUDO_UID Set to the user-ID of the user who invoked sudo. SUDO_USER Set to the login name of the user who invoked sudo. USER Set to the same value as LOGNAME, described above. VISUAL Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set. FILES top /etc/sudo.conf front-end configuration EXAMPLES top The following examples assume a properly configured security policy. To get a file listing of an unreadable directory: $ sudo ls /usr/local/protected To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root: $ sudo -u yaz ls ~yaz To edit the index.html file as user www: $ sudoedit -u www ~www/htdocs/index.html To view system logs only accessible to root and users in the adm group: $ sudo -g adm more /var/log/syslog To run an editor as jim with a different primary group: $ sudoedit -u jim -g audio ~jim/sound.txt To shut down a machine: $ sudo shutdown -r +15 "quick reboot" To make a usage listing of the directories in the /home partition. The commands are run in a sub-shell to allow the cd command and file redirection to work. $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" DIAGNOSTICS top Error messages produced by include: editing files in a writable directory is not permitted By default, sudoedit does not permit editing a file when any of the parent directories are writable by the invoking user. This avoids a race condition that could allow the user to overwrite an arbitrary file. See the sudoedit_checkdir option in sudoers(5) for more information. editing symbolic links is not permitted By default, sudoedit does not follow symbolic links when opening files. See the sudoedit_follow option in sudoers(5) for more information. effective uid is not 0, is sudo installed setuid root? was not run with root privileges. The binary must be owned by the root user and have the set-user-ID bit set. Also, it must not be located on a file system mounted with the nosuid option or on an NFS file system that maps uid 0 to an unprivileged uid. effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges? was not run with root privileges. The binary has the proper owner and permissions but it still did not run with root privileges. The most common reason for this is that the file system the binary is located on is mounted with the nosuid option or it is an NFS file system that maps uid 0 to an unprivileged uid. fatal error, unable to load plugins An error occurred while loading or initializing the plugins specified in sudo.conf(5). invalid environment variable name One or more environment variable names specified via the -E option contained an equal sign (=). The arguments to the -E option should be environment variable names without an associated value. no password was provided When tried to read the password, it did not receive any characters. This may happen if no terminal is available (or the -S option is specified) and the standard input has been redirected from /dev/null. a terminal is required to read the password needs to read the password but there is no mechanism available for it to do so. A terminal is not present to read the password from, has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the sudo.conf(5) file or the SUDO_ASKPASS environment variable. no writable temporary directory found sudoedit was unable to find a usable temporary directory in which to store its intermediate files. The no new privileges flag is set, which prevents sudo from running as root. was run by a process that has the Linux no new privileges flag is set. This causes the set-user-ID bit to be ignored when running an executable, which will prevent from functioning. The most likely cause for this is running within a container that sets this flag. Check the documentation to see if it is possible to configure the container such that the flag is not set. sudo must be owned by uid 0 and have the setuid bit set was not run with root privileges. The binary does not have the correct owner or permissions. It must be owned by the root user and have the set-user-ID bit set. sudoedit is not supported on this platform It is only possible to run sudoedit on systems that support setting the effective user-ID. timed out reading password The user did not enter a password before the password timeout (5 minutes by default) expired. you do not exist in the passwd database Your user-ID does not appear in the system passwd database. you may not specify environment variables in edit mode It is only possible to specify environment variables when running a command. When editing a file, the editor is run with the user's environment unmodified. SEE ALSO top su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8) HISTORY top See the HISTORY.md file in the distribution (https://www.sudo.ws/about/history/) for a brief history of sudo. AUTHORS top Many people have worked on over the years; this version consists of code written primarily by: Todd C. Miller See the CONTRIBUTORS.md file in the distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed to . CAVEATS top There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via . Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with the sudoers(5) plugin's noexec functionality. It is not meaningful to run the cd command directly via sudo, e.g., $ sudo cd /usr/local/protected since when the command exits the parent process (your shell) will still be the same. The -D option can be used to run a command in a specific directory. Running shell scripts via can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, set-user-ID shell scripts are generally safe). BUGS top If you believe you have found a bug in , you can submit a bug report at https://bugzilla.sudo.ws/ SUPPORT top Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives. DISCLAIMER top is provided AS IS and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE.md file distributed with or https://www.sudo.ws/about/license/ for complete details. COLOPHON top This page is part of the sudo (execute a command as another user) project. Information about the project can be found at https://www.sudo.ws/. If you have a bug report for this manual page, see https://bugzilla.sudo.ws/. This page was obtained from the project's upstream Git repository https://github.com/sudo-project/sudo on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Sudo 1.9.15p4 August 9, 2023 SUDO(8) Pages that refer to this page: homectl(1), journalctl(1), localectl(1), loginctl(1), machinectl(1), portablectl(1), setpriv(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), uid0(1), userdbctl(1), nsswitch.conf(5), credentials(7), systemd-tmpfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner to "hduser" and group to "hadoop" of "{directory path}" Bash Command:<START>sudo chown hduser:hadoop {directory path}<END>

Change the owner to "owner" and group to "nobody" of "public_html"

chown owner:nobody public_html

['chown']

Output a Bash command to accomplish the following task. Task: Change the owner to "owner" and group to "nobody" of "public_html" Bash Command:<START>chown owner:nobody public_html<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner to "owner" and group to "nobody" of "public_html" Bash Command:<START>chown owner:nobody public_html<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner to "owner" and group to "nobody" of "public_html" Bash Command:<START>chown owner:nobody public_html<END>

Change the owner to "root" and group to "specialusers" of "dir1"

chown root:specialusers dir1

['chown']

Output a Bash command to accomplish the following task. Task: Change the owner to "root" and group to "specialusers" of "dir1" Bash Command:<START>chown root:specialusers dir1<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner to "root" and group to "specialusers" of "dir1" Bash Command:<START>chown root:specialusers dir1<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner to "root" and group to "specialusers" of "dir1" Bash Command:<START>chown root:specialusers dir1<END>

Change the owner to "user" and group to "group" of files "file ..."

chown user:group file ...

['file', 'chown']

Output a Bash command to accomplish the following task. Task: Change the owner to "user" and group to "group" of files "file ..." Bash Command:<START>chown user:group file ...<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # file\n\n> Determine file type.\n> More information: <https://manned.org/file>.\n\n- Give a description of the type of the specified file. Works fine for files with no file extension:\n\n`file {{path/to/file}}`\n\n- Look inside a zipped file and determine the file type(s) inside:\n\n`file -z {{foo.zip}}`\n\n- Allow file to work with special or device files:\n\n`file -s {{path/to/file}}`\n\n- Don't stop at first file type match; keep going until the end of the file:\n\n`file -k {{path/to/file}}`\n\n- Determine the MIME encoding type of a file:\n\n`file -i {{path/to/file}}`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the owner to "user" and group to "group" of files "file ..." Bash Command:<START>chown user:group file ...<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: file(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training file(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | FILES | EXIT STATUS | EXAMPLES | SEE ALSO | STANDARDS CONFORMANCE | SECURITY | MAGIC DIRECTORY | HISTORY | LEGAL NOTICE | BUGS | TODO | AVAILABILITY | COLOPHON FILE(1) General Commands Manual FILE(1) NAME top file determine file type SYNOPSIS top [-bcdEhiklLNnprsSvzZ0] [--apple] [--exclude-quiet] [--extension] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile] [-m magicfiles] [-P name=value] file ... -C [-m magicfiles] [--help] DESCRIPTION top This manual page documents version 5.45 of the command. tests each argument in an attempt to classify it. There are three sets of tests, performed in this order: filesystem tests, magic tests, and language tests. The first test that succeeds causes the file type to be printed. The type printed will usually contain one of the words text (the file contains only printing characters and a few common control characters and is probably safe to read on an ASCII terminal), executable (the file contains the result of compiling a program in a form understandable to some UNIX kernel or another), or data meaning anything else (data is usually binary or non- printable). Exceptions are well-known file formats (core files, tar archives) that are known to contain binary data. When modifying magic files or the program itself, make sure to preserve these keywords. Users depend on knowing that all the readable files in a directory have the word text printed. Don't do as Berkeley did and change shell commands text to shell script. The filesystem tests are based on examining the return from a stat(2) system call. The program checks to see if the file is empty, or if it's some sort of special file. Any known file types appropriate to the system you are running on (sockets, symbolic links, or named pipes (FIFOs) on those systems that implement them) are intuited if they are defined in the system header file <sys/stat.h>. The magic tests are used to check for files with data in particular fixed formats. The canonical example of this is a binary executable (compiled program) a.out file, whose format is defined in <elf.h>, <a.out.h> and possibly <exec.h> in the standard include directory. These files have a magic number stored in a particular place near the beginning of the file that tells the UNIX operating system that the file is a binary executable, and which of several types thereof. The concept of a magic number has been applied by extension to data files. Any file with some invariant identifier at a small fixed offset into the file can usually be described in this way. The information identifying these files is read from the compiled magic file /usr/local/share/misc/magic.mgc, or the files in the directory /usr/local/share/misc/magic if the compiled file does not exist. In addition, if $HOME/.magic.mgc or $HOME/.magic exists, it will be used in preference to the system magic files. If a file does not match any of the entries in the magic file, it is examined to see if it seems to be a text file. ASCII, ISO-8859-x, non-ISO 8-bit extended-ASCII character sets (such as those used on Macintosh and IBM PC systems), UTF-8-encoded Unicode, UTF-16-encoded Unicode, and EBCDIC character sets can be distinguished by the different ranges and sequences of bytes that constitute printable text in each set. If a file passes any of these tests, its character set is reported. ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified as text because they will be mostly readable on nearly any terminal; UTF-16 and EBCDIC are only character data because, while they contain text, it is text that will require translation before it can be read. In addition, will attempt to determine other characteristics of text-type files. If the lines of a file are terminated by CR, CRLF, or NEL, instead of the Unix-standard LF, this will be reported. Files that contain embedded escape sequences or overstriking will also be identified. Once has determined the character set used in a text-type file, it will attempt to determine in what language the file is written. The language tests look for particular strings (cf. <names.h>) that can appear anywhere in the first few blocks of a file. For example, the keyword .br indicates that the file is most likely a troff(1) input file, just as the keyword struct indicates a C program. These tests are less reliable than the previous two groups, so they are performed last. The language test routines also test for some miscellany (such as tar(1) archives, JSON files). Any file that cannot be identified as having been written in any of the character sets listed above is simply said to be data. OPTIONS top --apple Causes the command to output the file type and creator code as used by older MacOS versions. The code consists of eight letters, the first describing the file type, the latter the creator. This option works properly only for file formats that have the apple-style output defined. -b, --brief Do not prepend filenames to output lines (brief mode). -C, --compile Write a magic.mgc output file that contains a pre-parsed version of the magic file or directory. -c, --checking-printout Cause a checking printout of the parsed form of the magic file. This is usually used in conjunction with the -m option to debug a new magic file before installing it. -d Prints internal debugging information to stderr. -E On filesystem errors (file not found etc), instead of handling the error as regular output as POSIX mandates and keep going, issue an error message and exit. -e, --exclude testname Exclude the test named in testname from the list of tests made to determine the file type. Valid test names are: apptype EMX application type (only on EMX). ascii Various types of text files (this test will try to guess the text encoding, irrespective of the setting of the encoding option). encoding Different text encodings for soft magic tests. tokens Ignored for backwards compatibility. cdf Prints details of Compound Document Files. compress Checks for, and looks inside, compressed files. csv Checks Comma Separated Value files. elf Prints ELF file details, provided soft magic tests are enabled and the elf magic is found. json Examines JSON (RFC-7159) files by parsing them for compliance. soft Consults magic files. simh Examines SIMH tape files. tar Examines tar files by verifying the checksum of the 512 byte tar header. Excluding this test can provide more detailed content description by using the soft magic method. text A synonym for ascii. --exclude-quiet Like --exclude but ignore tests that does not know about. This is intended for compatibility with older versions of . --extension Print a slash-separated list of valid extensions for the file type found. -F, --separator separator Use the specified string as the separator between the filename and the file result returned. Defaults to :. -f, --files-from namefile Read the names of the files to be examined from namefile (one per line) before the argument list. Either namefile or at least one filename argument must be present; to test the standard input, use - as a filename argument. Please note that namefile is unwrapped and the enclosed filenames are processed when this option is encountered and before any further options processing is done. This allows one to process multiple lists of files with different command line arguments on the same invocation. Thus if you want to set the delimiter, you need to do it before you specify the list of files, like: -F @ -f namefile, instead of: -f namefile -F @. -h, --no-dereference This option causes symlinks not to be followed (on systems that support symbolic links). This is the default if the environment variable POSIXLY_CORRECT is not defined. -i, --mime Causes the command to output mime type strings rather than the more traditional human readable ones. Thus it may say text/plain; charset=us-ascii rather than ASCII text. --mime-type, --mime-encoding Like -i, but print only the specified element(s). -k, --keep-going Don't stop at the first match, keep going. Subsequent matches will be have the string \012- prepended. (If you want a newline, see the -r option.) The magic pattern with the highest strength (see the -l option) comes first. -l, --list Shows a list of patterns and their strength sorted descending by magic(4) strength which is used for the matching (see also the -k option). -L, --dereference This option causes symlinks to be followed, as the like- named option in ls(1) (on systems that support symbolic links). This is the default if the environment variable POSIXLY_CORRECT is defined. -m, --magic-file magicfiles Specify an alternate list of files and directories containing magic. This can be a single item, or a colon- separated list. If a compiled magic file is found alongside a file or directory, it will be used instead. -N, --no-pad Don't pad filenames so that they align in the output. -n, --no-buffer Force stdout to be flushed after checking each file. This is only useful if checking a list of files. It is intended to be used by programs that want filetype output from a pipe. -p, --preserve-date On systems that support utime(3) or utimes(2), attempt to preserve the access time of files analyzed, to pretend that never read them. -P, --parameter name=value Set various parameter limits. Name Default Explanation bytes 1M max number of bytes to read from file elf_notes 256 max ELF notes processed elf_phnum 2K max ELF program sections processed elf_shnum 32K max ELF sections processed elf_shsize 128MB max ELF section size processed encoding 65K max number of bytes to determine encoding indir 50 recursion limit for indirect magic name 50 use count limit for name/use magic regex 8K length limit for regex searches -r, --raw Don't translate unprintable characters to \ooo. Normally translates unprintable characters to their octal representation. -s, --special-files Normally, only attempts to read and determine the type of argument files which stat(2) reports are ordinary files. This prevents problems, because reading special files may have peculiar consequences. Specifying the -s option causes to also read argument files which are block or character special files. This is useful for determining the filesystem types of the data in raw disk partitions, which are block special files. This option also causes to disregard the file size as reported by stat(2) since on some systems it reports a zero size for raw disk partitions. -S, --no-sandbox On systems where libseccomp (https://github.com/seccomp/libseccomp ) is available, the -S option disables sandboxing which is enabled by default. This option is needed for to execute external decompressing programs, i.e. when the -z option is specified and the built-in decompressors are not available. On systems where sandboxing is not available, this option has no effect. -v, --version Print the version of the program and exit. -z, --uncompress Try to look inside compressed files. -Z, --uncompress-noreport Try to look inside compressed files, but report information about the contents only not the compression. -0, --print0 Output a null character \0 after the end of the filename. Nice to cut(1) the output. This does not affect the separator, which is still printed. If this option is repeated more than once, then prints just the filename followed by a NUL followed by the description (or ERROR: text) followed by a second NUL for each entry. --help Print a help message and exit. ENVIRONMENT top The environment variable MAGIC can be used to set the default magic file name. If that variable is set, then will not attempt to open $HOME/.magic. adds .mgc to the value of this variable as appropriate. The environment variable POSIXLY_CORRECT controls (on systems that support symbolic links), whether will attempt to follow symlinks or not. If set, then follows symlink, otherwise it does not. This is also controlled by the -L and -h options. FILES top /usr/local/share/misc/magic.mgc Default compiled list of magic. /usr/local/share/misc/magic Directory containing default magic files. EXIT STATUS top will exit with 0 if the operation was successful or >0 if an error was encountered. The following errors cause diagnostic messages, but don't affect the program exit code (as POSIX requires), unless -E is specified: A file cannot be found There is no permission to read a file The file type cannot be determined EXAMPLES top $ file file.c file /dev/{wd0a,hda} file.c: C program text file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), stripped /dev/wd0a: block special (0/0) /dev/hda: block special (3/0) $ file -s /dev/wd0{b,d} /dev/wd0b: data /dev/wd0d: x86 boot sector $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} /dev/hda: x86 boot sector /dev/hda1: Linux/i386 ext2 filesystem /dev/hda2: x86 boot sector /dev/hda3: x86 boot sector, extended partition table /dev/hda4: Linux/i386 ext2 filesystem /dev/hda5: Linux/i386 swap file /dev/hda6: Linux/i386 swap file /dev/hda7: Linux/i386 swap file /dev/hda8: Linux/i386 swap file /dev/hda9: empty /dev/hda10: empty $ file -i file.c file /dev/{wd0a,hda} file.c: text/x-c file: application/x-executable /dev/hda: application/x-not-regular-file /dev/wd0a: application/x-not-regular-file SEE ALSO top hexdump(1), od(1), strings(1), magic(4) STANDARDS CONFORMANCE top This program is believed to exceed the System V Interface Definition of FILE(CMD), as near as one can determine from the vague language contained therein. Its behavior is mostly compatible with the System V program of the same name. This version knows more magic, however, so it will produce different (albeit more accurate) output in many cases. The one significant difference between this version and System V is that this version treats any white space as a delimiter, so that spaces in pattern strings must be escaped. For example, >10 string language impress (imPRESS data) in an existing magic file would have to be changed to >10 string language\ impress (imPRESS data) In addition, in this version, if a pattern string contains a backslash, it must be escaped. For example 0 string \begindata Andrew Toolkit document in an existing magic file would have to be changed to 0 string \\begindata Andrew Toolkit document SunOS releases 3.2 and later from Sun Microsystems include a command derived from the System V one, but with some extensions. This version differs from Sun's only in minor ways. It includes the extension of the & operator, used as, for example, >16 long&0x7fffffff >0 not stripped SECURITY top On systems where libseccomp (https://github.com/seccomp/libseccomp ) is available, is enforces limiting system calls to only the ones necessary for the operation of the program. This enforcement does not provide any security benefit when is asked to decompress input files running external programs with the -z option. To enable execution of external decompressors, one needs to disable sandboxing using the -S option. MAGIC DIRECTORY top The magic file entries have been collected from various sources, mainly USENET, and contributed by various authors. Christos Zoulas (address below) will collect additional or corrected magic file entries. A consolidation of magic file entries will be distributed periodically. The order of entries in the magic file is significant. Depending on what system you are using, the order that they are put together may be incorrect. If your old command uses a magic file, keep the old magic file around for comparison purposes (rename it to /usr/local/share/misc/magic.orig). HISTORY top There has been a command in every UNIX since at least Research Version 4 (man page dated November, 1973). The System V version introduced one significant major change: the external list of magic types. This slowed the program down slightly but made it a lot more flexible. This program, based on the System V version, was written by Ian Darwin ian@darwinsys.com without looking at anybody else's source code. John Gilmore revised the code extensively, making it better than the first version. Geoff Collyer found several inadequacies and provided some magic file entries. Contributions of the & operator by Rob McMahon, cudcv@warwick.ac.uk, 1989. Guy Harris, guy@netapp.com, made many changes from 1993 to the present. Primary development and maintenance from 1990 to the present by Christos Zoulas christos@astron.com. Altered by Chris Lowth chris@lowth.com, 2000: handle the -i option to output mime type strings, using an alternative magic file and internal logic. Altered by Eric Fischer enf@pobox.com, July, 2000, to identify character codes and attempt to identify the languages of non- ASCII files. Altered by Reuben Thomas rrt@sc3d.org, 2007-2011, to improve MIME support, merge MIME and non-MIME magic, support directories as well as files of magic, apply many bug fixes, update and fix a lot of magic, improve the build system, improve the documentation, and rewrite the Python bindings in pure Python. The list of contributors to the magic directory (magic files) is too long to include here. You know who you are; thank you. Many contributors are listed in the source files. LEGAL NOTICE top Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. Covered by the standard Berkeley Software Distribution copyright; see the file COPYING in the source distribution. The files tar.h and is_tar.c were written by John Gilmore from his public-domain tar(1) program, and are not covered by the above license. BUGS top Please report bugs and send patches to the bug tracker at https://bugs.astron.com/ or the mailing list at file@astron.com (visit https://mailman.astron.com/mailman/listinfo/file first to subscribe). TODO top Fix output so that tests for MIME and APPLE flags are not needed all over the place, and actual output is only done in one place. This needs a design. Suggestion: push possible outputs on to a list, then pick the last-pushed (most specific, one hopes) value at the end, or use a default if the list is empty. This should not slow down evaluation. The handling of MAGIC_CONTINUE and printing \012- between entries is clumsy and complicated; refactor and centralize. Some of the encoding logic is hard-coded in encoding.c and can be moved to the magic files if we had a !:charset annotation. Continue to squash all magic bugs. See Debian BTS for a good source. Store arbitrarily long strings, for example for %s patterns, so that they can be printed out. Fixes Debian bug #271672. This can be done by allocating strings in a string pool, storing the string pool at the end of the magic file and converting all the string pointers to relative offsets from the string pool. Add syntax for relative offsets after current level (Debian bug #466037). Make file -ki work, i.e. give multiple MIME types. Add a zip library so we can peek inside Office2007 documents to print more details about their contents. Add an option to print URLs for the sources of the file descriptions. Combine script searches and add a way to map executable names to MIME types (e.g. have a magic value for !:mime which causes the resulting string to be looked up in a table). This would avoid adding the same magic repeatedly for each new hash-bang interpreter. When a file descriptor is available, we can skip and adjust the buffer instead of the hacky buffer management we do now. Fix name and use to check for consistency at compile time (duplicate name, use pointing to undefined name ). Make name / use more efficient by keeping a sorted list of names. Special-case ^ to flip endianness in the parser so that it does not have to be escaped, and document it. If the offsets specified internally in the file exceed the buffer size ( HOWMANY variable in file.h), then we don't seek to that offset, but we give up. It would be better if buffer managements was done when the file descriptor is available so we can seek around the file. One must be careful though because this has performance and thus security considerations, because one can slow down things by repeatedly seeking. There is support now for keeping separate buffers and having offsets from the end of the file, but the internal buffer management still needs an overhaul. AVAILABILITY top You can obtain the original author's latest version by anonymous FTP on ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz. COLOPHON top This page is part of the file (a file type guesser) project. Information about the project can be found at http://www.darwinsys.com/file/. If you have a bug report for this manual page, see http://bugs.gw.com/my_view_page.php. This page was obtained from the project's upstream Git read-only mirror of the CVS repository https://github.com/glensc/file on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU May 21, 2023 FILE(1) Pages that refer to this page: dh_installmanpages(1), dh_strip(1), ippeveprinter(1), pmcd(1), scr_dump(5), term(5), suffixes(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the owner to "user" and group to "group" of files "file ..." Bash Command:<START>chown user:group file ...<END>

Change the ownership of "/etc/udev/rules.d/51-android.rules" to "root"

sudo chown root. /etc/udev/rules.d/51-android.rules

['chown', 'sudo']

Output a Bash command to accomplish the following task. Task: Change the ownership of "/etc/udev/rules.d/51-android.rules" to "root" Bash Command:<START>sudo chown root. /etc/udev/rules.d/51-android.rules<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n # sudo\n\n> Executes a single command as the superuser or another user.\n> More information: <https://www.sudo.ws/sudo.html>.\n\n- Run a command as the superuser:\n\n`sudo {{less /var/log/syslog}}`\n\n- Edit a file as the superuser with your default editor:\n\n`sudo --edit {{/etc/fstab}}`\n\n- Run a command as another user and/or group:\n\n`sudo --user={{user}} --group={{group}} {{id -a}}`\n\n- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):\n\n`sudo !!`\n\n- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login`\n\n- Launch the default shell with superuser privileges without changing the environment:\n\n`sudo --shell`\n\n- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login --user={{user}}`\n\n- List the allowed (and forbidden) commands for the invoking user:\n\n`sudo --list`\n Task: Change the ownership of "/etc/udev/rules.d/51-android.rules" to "root" Bash Command:<START>sudo chown root. /etc/udev/rules.d/51-android.rules<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sudo(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sudo(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON SUDO(8) System Manager's Manual SUDO(8) NAME top sudo, sudoedit execute a command as another user SYNOPSIS top sudo -h | -K | -k | -V sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command [arg ...]] sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] [VAR=value] [-i | -s] [command [arg ...]] sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] file ... DESCRIPTION top allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy. supports a plugin architecture for security policies, auditing, and input/output logging. Third parties can develop and distribute their own plugins to work seamlessly with the front- end. The default security policy is sudoers, which is configured via the file /etc/sudoers, or via LDAP. See the Plugins section for more information. The security policy determines what privileges, if any, a user has to run . The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific; the default password prompt timeout for the sudoers security policy is 5 minutes. Security policies may support credential caching to allow the user to run again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running with the -v option, a user can update the cached credentials without running a command. On systems where is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced. When invoked as sudoedit, the -e option (described below), is implied. Security policies and audit plugins may log successful and failed attempts to run . If an I/O plugin is configured, the running command's input and output may be logged as well. The options are as follows: -A, --askpass Normally, if requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example: # Path to askpass helper program Path askpass /usr/X11R6/bin/ssh-askpass If no askpass program is available, will exit with an error. -B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used. -b, --background Run the given command in the background. It is not possible to use shell job control to manipulate background processes started by . Most interactive commands will fail to work properly in background mode. -C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, will close all open file descriptors other than standard input, standard output, and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option. -D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory. -E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment. --preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times. -e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken: 1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used. 3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy: Symbolic links may not be edited (version 1.8.15 and higher). Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher). Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher). Users are never allowed to edit device special files. If the specified file does not exist, it will be created. Unlike most commands run by sudo, the editor is run with the invoking user's environment unmodified. If the temporary file becomes empty after editing, the user will be prompted before it is installed. If, for some reason, is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file. -g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the # character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the # be escaped with a backslash (\). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use. -H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior. -h, --help Display a short help message to the standard output and exit. -h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. The sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host. -i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login- specific resource files such as .profile, .bash_profile, or .login will be read by the shell. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use. -K, --remove-timestamp Similar to the -k option, except that it removes every cached credential for the user, regardless of the terminal or parent process ID. The next time is run, a password must be entered if the security policy requires authentication. It is not possible to use the -K option in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching. -k, --reset-timestamp When used without a command, invalidates the user's cached credentials for the current session. The next time is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with commands run in a different terminal session. See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke permissions from a .logout file. When used in conjunction with a command or an option that may require a password, this option will cause to ignore the user's cached credentials. As a result, will prompt for a password (if one is required by the security policy) and will not update the user's cached credentials. Not all security policies support credential caching. -l, --list If no command is specified, list the privileges for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format. If a command is specified and is permitted by the security policy for the invoking user (or the, user specified by the -U option) on the current host, the fully-qualified path to the command is displayed along with any args. If -l is specified more than once (and the security policy supports it), the matching rule is displayed in a verbose format along with the command. If a command is specified but not allowed by the policy, will exit with a status value of 1. -N, --no-update Do not update the user's cached credentials, even if the user successfully authenticates. Unlike the -k flag, existing cached credentials are used if they are valid. To detect when the user's cached credentials are valid (or when no authentication is required), the following can be used: sudo -Nnv Not all security policies support credential caching. -n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, will display an error message and exit. -P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user. -p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent (%) escape sequences are supported by the sudoers policy: %H expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in sudoers(5)) %h expanded to the local host name without the domain name %p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5)) %U expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified) %u expanded to the invoking user's login name %% two consecutive % characters are collapsed into a single % character The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers. -R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory. -S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device. -s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. -U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. When using the sudoers policy, the -U option is restricted to the root user and users with either the list priviege for the specified user or the ability to run any command as root or user on the current host. -T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the user's ability to set timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled. -u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the # character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the # be escaped with a backslash (\). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this. -V, --version Print the version string as well as the version string of any configured plugins. If the invoking user is already root, the -V option will display the options passed to configure when was built; plugins may display additional information such as default options. -v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials. -- The -- is used to delimit the end of the options. Subsequent options are passed to the command. Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input. Environment variables to be set for the command may also be passed as options to in the form VAR=value, for example LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be subject to restrictions imposed by the security policy plugin. The sudoers policy subjects environment variables passed as options to the same restrictions as existing environment variables with one important difference. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information. COMMAND EXECUTION top When executes a command, the security policy specifies the execution environment for the command. Typically, the real and effective user and group and IDs are set to match those of the target user, as specified in the password database, and the group vector is initialized based on the group database (unless the -P option was specified). The following parameters may be specified by security policy: real and effective user-ID real and effective group-ID supplementary group-IDs the environment list current working directory file creation mode mask (umask) scheduling priority (aka nice value) Process model There are two distinct ways can run a command. If an I/O logging plugin is configured to log terminal I/O, or if the security policy explicitly requests it, a new pseudo-terminal (pty) is allocated and fork(2) is used to create a second process, referred to as the monitor. The monitor creates a new terminal session with itself as the leader and the pty as its controlling terminal, calls fork(2) again, sets up the execution environment as described above, and then uses the execve(2) system call to run the command in the child process. The monitor exists to relay job control signals between the user's terminal and the pty the command is being run in. This makes it possible to suspend and resume the command normally. Without the monitor, the command would be in what POSIX terms an orphaned process group and it would not receive any job control signals from the kernel. When the command exits or is terminated by a signal, the monitor passes the command's exit status to the main process and exits. After receiving the command's exit status, the main process passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugin, and exits. This mode is the default for sudo versions 1.9.14 and above when using the sudoers policy. If no pty is used, calls fork(2), sets up the execution environment as described above, and uses the execve(2) system call to run the command in the child process. The main process waits until the command has completed, then passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugins, and exits. As a special case, if the policy plugin does not define a close function, will execute the command directly instead of calling fork(2) first. The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled. Both pam_session and pam_setcred are enabled by default on systems using PAM. This mode is the default for sudo versions prior to 1.9.14 when using the sudoers policy. On systems that use PAM, the security policy's close function is responsible for closing the PAM session. It may also log the command's exit status. Signal handling When the command is run as a child of the process, will relay signals it receives to the command. The SIGINT and SIGQUIT signals are only relayed when the command is being run in a new pty or when the signal was sent by a user process, not the kernel. This prevents the command from receiving SIGINT twice each time the user enters control-C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by . As a special case, will not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) utility sends SIGTERM to all non-system processes other than itself before rebooting the system. This prevents from relaying the SIGTERM signal it received back to reboot(8), which might then exit before the system was actually rebooted, leaving it in a half-dead state similar to single user mode. Note, however, that this check only applies to the command run by and not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via may cause the system to end up in this undefined state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the command and the calling process). Plugins Plugins may be specified via Plugin directives in the sudo.conf(5) file. They may be loaded as dynamic shared objects (on systems that support them), or compiled directly into the binary. If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, will use sudoers(5) for the policy, auditing, and I/O logging plugins. See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for more information about the plugin architecture. EXIT VALUE top Upon successful execution of a command, the exit status from will be the exit status of the program that was executed. If the command terminated due to receipt of a signal, will send itself the same signal that terminated the command. If the -l option was specified without a command, will exit with a value of 0 if the user is allowed to run and they authenticated successfully (as required by the security policy). If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by the security policy, otherwise it will be 1. If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, exits with a value of 1. In the latter case, the error string is printed to the standard error. If cannot stat(2) one or more entries in the user's PATH, an error is printed to the standard error. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat(2) to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. SECURITY NOTES top tries to be safe when executing external commands. To prevent command spoofing, checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the program that executes. Users should never be granted privileges to execute files that are writable by the user or that reside in a directory that is writable by the user. If the user can modify or replace the command there is no way to limit what additional commands they can run. By default, will only log the command it explicitly runs. If a user runs a command such as sudo su or sudo sh, subsequent commands run from that shell are not subject to sudo's security policy. The same is true for commands that offer shell escapes (including most editors). If I/O logging is enabled, subsequent commands will have their input and/or output logged, but there will not be traditional logs for those commands. Because of this, care must be taken when giving users access to commands via to verify that the command does not inadvertently give the user an effective root shell. For information on ways to address this, see the Preventing shell escapes section in sudoers(5). To prevent the disclosure of potentially sensitive information, disables core dumps by default while it is executing (they are re-enabled for the command that is run). This historical practice dates from a time when most operating systems allowed set-user-ID processes to dump core by default. To aid in debugging crashes, you may wish to re-enable core dumps by setting disable_coredump to false in the sudo.conf(5) file as follows: Set disable_coredump false See the sudo.conf(5) manual for more information. ENVIRONMENT top utilizes the following environment variables. The security policy has control over the actual content of the command's environment. EDITOR Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set. MAIL Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is present in the env_keep list). HOME Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the env_keep list. LOGNAME Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list). PATH May be overridden by the security policy. SHELL Used to determine shell to run with -s option. SUDO_ASKPASS Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified. SUDO_COMMAND Set to the command run by sudo, including any args. The args are truncated at 4096 characters to prevent a potential execution error. SUDO_EDITOR Default editor to use in -e (sudoedit) mode. SUDO_GID Set to the group-ID of the user who invoked sudo. SUDO_PROMPT Used as the default password prompt unless the -p option was specified. SUDO_PS1 If set, PS1 will be set to its value for the program being run. SUDO_UID Set to the user-ID of the user who invoked sudo. SUDO_USER Set to the login name of the user who invoked sudo. USER Set to the same value as LOGNAME, described above. VISUAL Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set. FILES top /etc/sudo.conf front-end configuration EXAMPLES top The following examples assume a properly configured security policy. To get a file listing of an unreadable directory: $ sudo ls /usr/local/protected To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root: $ sudo -u yaz ls ~yaz To edit the index.html file as user www: $ sudoedit -u www ~www/htdocs/index.html To view system logs only accessible to root and users in the adm group: $ sudo -g adm more /var/log/syslog To run an editor as jim with a different primary group: $ sudoedit -u jim -g audio ~jim/sound.txt To shut down a machine: $ sudo shutdown -r +15 "quick reboot" To make a usage listing of the directories in the /home partition. The commands are run in a sub-shell to allow the cd command and file redirection to work. $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" DIAGNOSTICS top Error messages produced by include: editing files in a writable directory is not permitted By default, sudoedit does not permit editing a file when any of the parent directories are writable by the invoking user. This avoids a race condition that could allow the user to overwrite an arbitrary file. See the sudoedit_checkdir option in sudoers(5) for more information. editing symbolic links is not permitted By default, sudoedit does not follow symbolic links when opening files. See the sudoedit_follow option in sudoers(5) for more information. effective uid is not 0, is sudo installed setuid root? was not run with root privileges. The binary must be owned by the root user and have the set-user-ID bit set. Also, it must not be located on a file system mounted with the nosuid option or on an NFS file system that maps uid 0 to an unprivileged uid. effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges? was not run with root privileges. The binary has the proper owner and permissions but it still did not run with root privileges. The most common reason for this is that the file system the binary is located on is mounted with the nosuid option or it is an NFS file system that maps uid 0 to an unprivileged uid. fatal error, unable to load plugins An error occurred while loading or initializing the plugins specified in sudo.conf(5). invalid environment variable name One or more environment variable names specified via the -E option contained an equal sign (=). The arguments to the -E option should be environment variable names without an associated value. no password was provided When tried to read the password, it did not receive any characters. This may happen if no terminal is available (or the -S option is specified) and the standard input has been redirected from /dev/null. a terminal is required to read the password needs to read the password but there is no mechanism available for it to do so. A terminal is not present to read the password from, has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the sudo.conf(5) file or the SUDO_ASKPASS environment variable. no writable temporary directory found sudoedit was unable to find a usable temporary directory in which to store its intermediate files. The no new privileges flag is set, which prevents sudo from running as root. was run by a process that has the Linux no new privileges flag is set. This causes the set-user-ID bit to be ignored when running an executable, which will prevent from functioning. The most likely cause for this is running within a container that sets this flag. Check the documentation to see if it is possible to configure the container such that the flag is not set. sudo must be owned by uid 0 and have the setuid bit set was not run with root privileges. The binary does not have the correct owner or permissions. It must be owned by the root user and have the set-user-ID bit set. sudoedit is not supported on this platform It is only possible to run sudoedit on systems that support setting the effective user-ID. timed out reading password The user did not enter a password before the password timeout (5 minutes by default) expired. you do not exist in the passwd database Your user-ID does not appear in the system passwd database. you may not specify environment variables in edit mode It is only possible to specify environment variables when running a command. When editing a file, the editor is run with the user's environment unmodified. SEE ALSO top su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8) HISTORY top See the HISTORY.md file in the distribution (https://www.sudo.ws/about/history/) for a brief history of sudo. AUTHORS top Many people have worked on over the years; this version consists of code written primarily by: Todd C. Miller See the CONTRIBUTORS.md file in the distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed to . CAVEATS top There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via . Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with the sudoers(5) plugin's noexec functionality. It is not meaningful to run the cd command directly via sudo, e.g., $ sudo cd /usr/local/protected since when the command exits the parent process (your shell) will still be the same. The -D option can be used to run a command in a specific directory. Running shell scripts via can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, set-user-ID shell scripts are generally safe). BUGS top If you believe you have found a bug in , you can submit a bug report at https://bugzilla.sudo.ws/ SUPPORT top Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives. DISCLAIMER top is provided AS IS and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE.md file distributed with or https://www.sudo.ws/about/license/ for complete details. COLOPHON top This page is part of the sudo (execute a command as another user) project. Information about the project can be found at https://www.sudo.ws/. If you have a bug report for this manual page, see https://bugzilla.sudo.ws/. This page was obtained from the project's upstream Git repository https://github.com/sudo-project/sudo on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Sudo 1.9.15p4 August 9, 2023 SUDO(8) Pages that refer to this page: homectl(1), journalctl(1), localectl(1), loginctl(1), machinectl(1), portablectl(1), setpriv(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), uid0(1), userdbctl(1), nsswitch.conf(5), credentials(7), systemd-tmpfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the ownership of "/etc/udev/rules.d/51-android.rules" to "root" Bash Command:<START>sudo chown root. /etc/udev/rules.d/51-android.rules<END>

Change the ownership of "/home/bob" to "root"

sudo chown root /home/bob

['chown', 'sudo']

Output a Bash command to accomplish the following task. Task: Change the ownership of "/home/bob" to "root" Bash Command:<START>sudo chown root /home/bob<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n # sudo\n\n> Executes a single command as the superuser or another user.\n> More information: <https://www.sudo.ws/sudo.html>.\n\n- Run a command as the superuser:\n\n`sudo {{less /var/log/syslog}}`\n\n- Edit a file as the superuser with your default editor:\n\n`sudo --edit {{/etc/fstab}}`\n\n- Run a command as another user and/or group:\n\n`sudo --user={{user}} --group={{group}} {{id -a}}`\n\n- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):\n\n`sudo !!`\n\n- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login`\n\n- Launch the default shell with superuser privileges without changing the environment:\n\n`sudo --shell`\n\n- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login --user={{user}}`\n\n- List the allowed (and forbidden) commands for the invoking user:\n\n`sudo --list`\n Task: Change the ownership of "/home/bob" to "root" Bash Command:<START>sudo chown root /home/bob<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sudo(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sudo(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON SUDO(8) System Manager's Manual SUDO(8) NAME top sudo, sudoedit execute a command as another user SYNOPSIS top sudo -h | -K | -k | -V sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command [arg ...]] sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] [VAR=value] [-i | -s] [command [arg ...]] sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] file ... DESCRIPTION top allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy. supports a plugin architecture for security policies, auditing, and input/output logging. Third parties can develop and distribute their own plugins to work seamlessly with the front- end. The default security policy is sudoers, which is configured via the file /etc/sudoers, or via LDAP. See the Plugins section for more information. The security policy determines what privileges, if any, a user has to run . The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific; the default password prompt timeout for the sudoers security policy is 5 minutes. Security policies may support credential caching to allow the user to run again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running with the -v option, a user can update the cached credentials without running a command. On systems where is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced. When invoked as sudoedit, the -e option (described below), is implied. Security policies and audit plugins may log successful and failed attempts to run . If an I/O plugin is configured, the running command's input and output may be logged as well. The options are as follows: -A, --askpass Normally, if requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example: # Path to askpass helper program Path askpass /usr/X11R6/bin/ssh-askpass If no askpass program is available, will exit with an error. -B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used. -b, --background Run the given command in the background. It is not possible to use shell job control to manipulate background processes started by . Most interactive commands will fail to work properly in background mode. -C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, will close all open file descriptors other than standard input, standard output, and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option. -D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory. -E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment. --preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times. -e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken: 1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used. 3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy: Symbolic links may not be edited (version 1.8.15 and higher). Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher). Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher). Users are never allowed to edit device special files. If the specified file does not exist, it will be created. Unlike most commands run by sudo, the editor is run with the invoking user's environment unmodified. If the temporary file becomes empty after editing, the user will be prompted before it is installed. If, for some reason, is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file. -g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the # character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the # be escaped with a backslash (\). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use. -H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior. -h, --help Display a short help message to the standard output and exit. -h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. The sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host. -i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login- specific resource files such as .profile, .bash_profile, or .login will be read by the shell. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use. -K, --remove-timestamp Similar to the -k option, except that it removes every cached credential for the user, regardless of the terminal or parent process ID. The next time is run, a password must be entered if the security policy requires authentication. It is not possible to use the -K option in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching. -k, --reset-timestamp When used without a command, invalidates the user's cached credentials for the current session. The next time is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with commands run in a different terminal session. See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke permissions from a .logout file. When used in conjunction with a command or an option that may require a password, this option will cause to ignore the user's cached credentials. As a result, will prompt for a password (if one is required by the security policy) and will not update the user's cached credentials. Not all security policies support credential caching. -l, --list If no command is specified, list the privileges for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format. If a command is specified and is permitted by the security policy for the invoking user (or the, user specified by the -U option) on the current host, the fully-qualified path to the command is displayed along with any args. If -l is specified more than once (and the security policy supports it), the matching rule is displayed in a verbose format along with the command. If a command is specified but not allowed by the policy, will exit with a status value of 1. -N, --no-update Do not update the user's cached credentials, even if the user successfully authenticates. Unlike the -k flag, existing cached credentials are used if they are valid. To detect when the user's cached credentials are valid (or when no authentication is required), the following can be used: sudo -Nnv Not all security policies support credential caching. -n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, will display an error message and exit. -P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user. -p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent (%) escape sequences are supported by the sudoers policy: %H expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in sudoers(5)) %h expanded to the local host name without the domain name %p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5)) %U expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified) %u expanded to the invoking user's login name %% two consecutive % characters are collapsed into a single % character The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers. -R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory. -S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device. -s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. -U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. When using the sudoers policy, the -U option is restricted to the root user and users with either the list priviege for the specified user or the ability to run any command as root or user on the current host. -T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the user's ability to set timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled. -u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the # character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the # be escaped with a backslash (\). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this. -V, --version Print the version string as well as the version string of any configured plugins. If the invoking user is already root, the -V option will display the options passed to configure when was built; plugins may display additional information such as default options. -v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials. -- The -- is used to delimit the end of the options. Subsequent options are passed to the command. Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input. Environment variables to be set for the command may also be passed as options to in the form VAR=value, for example LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be subject to restrictions imposed by the security policy plugin. The sudoers policy subjects environment variables passed as options to the same restrictions as existing environment variables with one important difference. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information. COMMAND EXECUTION top When executes a command, the security policy specifies the execution environment for the command. Typically, the real and effective user and group and IDs are set to match those of the target user, as specified in the password database, and the group vector is initialized based on the group database (unless the -P option was specified). The following parameters may be specified by security policy: real and effective user-ID real and effective group-ID supplementary group-IDs the environment list current working directory file creation mode mask (umask) scheduling priority (aka nice value) Process model There are two distinct ways can run a command. If an I/O logging plugin is configured to log terminal I/O, or if the security policy explicitly requests it, a new pseudo-terminal (pty) is allocated and fork(2) is used to create a second process, referred to as the monitor. The monitor creates a new terminal session with itself as the leader and the pty as its controlling terminal, calls fork(2) again, sets up the execution environment as described above, and then uses the execve(2) system call to run the command in the child process. The monitor exists to relay job control signals between the user's terminal and the pty the command is being run in. This makes it possible to suspend and resume the command normally. Without the monitor, the command would be in what POSIX terms an orphaned process group and it would not receive any job control signals from the kernel. When the command exits or is terminated by a signal, the monitor passes the command's exit status to the main process and exits. After receiving the command's exit status, the main process passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugin, and exits. This mode is the default for sudo versions 1.9.14 and above when using the sudoers policy. If no pty is used, calls fork(2), sets up the execution environment as described above, and uses the execve(2) system call to run the command in the child process. The main process waits until the command has completed, then passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugins, and exits. As a special case, if the policy plugin does not define a close function, will execute the command directly instead of calling fork(2) first. The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled. Both pam_session and pam_setcred are enabled by default on systems using PAM. This mode is the default for sudo versions prior to 1.9.14 when using the sudoers policy. On systems that use PAM, the security policy's close function is responsible for closing the PAM session. It may also log the command's exit status. Signal handling When the command is run as a child of the process, will relay signals it receives to the command. The SIGINT and SIGQUIT signals are only relayed when the command is being run in a new pty or when the signal was sent by a user process, not the kernel. This prevents the command from receiving SIGINT twice each time the user enters control-C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by . As a special case, will not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) utility sends SIGTERM to all non-system processes other than itself before rebooting the system. This prevents from relaying the SIGTERM signal it received back to reboot(8), which might then exit before the system was actually rebooted, leaving it in a half-dead state similar to single user mode. Note, however, that this check only applies to the command run by and not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via may cause the system to end up in this undefined state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the command and the calling process). Plugins Plugins may be specified via Plugin directives in the sudo.conf(5) file. They may be loaded as dynamic shared objects (on systems that support them), or compiled directly into the binary. If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, will use sudoers(5) for the policy, auditing, and I/O logging plugins. See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for more information about the plugin architecture. EXIT VALUE top Upon successful execution of a command, the exit status from will be the exit status of the program that was executed. If the command terminated due to receipt of a signal, will send itself the same signal that terminated the command. If the -l option was specified without a command, will exit with a value of 0 if the user is allowed to run and they authenticated successfully (as required by the security policy). If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by the security policy, otherwise it will be 1. If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, exits with a value of 1. In the latter case, the error string is printed to the standard error. If cannot stat(2) one or more entries in the user's PATH, an error is printed to the standard error. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat(2) to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. SECURITY NOTES top tries to be safe when executing external commands. To prevent command spoofing, checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the program that executes. Users should never be granted privileges to execute files that are writable by the user or that reside in a directory that is writable by the user. If the user can modify or replace the command there is no way to limit what additional commands they can run. By default, will only log the command it explicitly runs. If a user runs a command such as sudo su or sudo sh, subsequent commands run from that shell are not subject to sudo's security policy. The same is true for commands that offer shell escapes (including most editors). If I/O logging is enabled, subsequent commands will have their input and/or output logged, but there will not be traditional logs for those commands. Because of this, care must be taken when giving users access to commands via to verify that the command does not inadvertently give the user an effective root shell. For information on ways to address this, see the Preventing shell escapes section in sudoers(5). To prevent the disclosure of potentially sensitive information, disables core dumps by default while it is executing (they are re-enabled for the command that is run). This historical practice dates from a time when most operating systems allowed set-user-ID processes to dump core by default. To aid in debugging crashes, you may wish to re-enable core dumps by setting disable_coredump to false in the sudo.conf(5) file as follows: Set disable_coredump false See the sudo.conf(5) manual for more information. ENVIRONMENT top utilizes the following environment variables. The security policy has control over the actual content of the command's environment. EDITOR Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set. MAIL Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is present in the env_keep list). HOME Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the env_keep list. LOGNAME Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list). PATH May be overridden by the security policy. SHELL Used to determine shell to run with -s option. SUDO_ASKPASS Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified. SUDO_COMMAND Set to the command run by sudo, including any args. The args are truncated at 4096 characters to prevent a potential execution error. SUDO_EDITOR Default editor to use in -e (sudoedit) mode. SUDO_GID Set to the group-ID of the user who invoked sudo. SUDO_PROMPT Used as the default password prompt unless the -p option was specified. SUDO_PS1 If set, PS1 will be set to its value for the program being run. SUDO_UID Set to the user-ID of the user who invoked sudo. SUDO_USER Set to the login name of the user who invoked sudo. USER Set to the same value as LOGNAME, described above. VISUAL Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set. FILES top /etc/sudo.conf front-end configuration EXAMPLES top The following examples assume a properly configured security policy. To get a file listing of an unreadable directory: $ sudo ls /usr/local/protected To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root: $ sudo -u yaz ls ~yaz To edit the index.html file as user www: $ sudoedit -u www ~www/htdocs/index.html To view system logs only accessible to root and users in the adm group: $ sudo -g adm more /var/log/syslog To run an editor as jim with a different primary group: $ sudoedit -u jim -g audio ~jim/sound.txt To shut down a machine: $ sudo shutdown -r +15 "quick reboot" To make a usage listing of the directories in the /home partition. The commands are run in a sub-shell to allow the cd command and file redirection to work. $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" DIAGNOSTICS top Error messages produced by include: editing files in a writable directory is not permitted By default, sudoedit does not permit editing a file when any of the parent directories are writable by the invoking user. This avoids a race condition that could allow the user to overwrite an arbitrary file. See the sudoedit_checkdir option in sudoers(5) for more information. editing symbolic links is not permitted By default, sudoedit does not follow symbolic links when opening files. See the sudoedit_follow option in sudoers(5) for more information. effective uid is not 0, is sudo installed setuid root? was not run with root privileges. The binary must be owned by the root user and have the set-user-ID bit set. Also, it must not be located on a file system mounted with the nosuid option or on an NFS file system that maps uid 0 to an unprivileged uid. effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges? was not run with root privileges. The binary has the proper owner and permissions but it still did not run with root privileges. The most common reason for this is that the file system the binary is located on is mounted with the nosuid option or it is an NFS file system that maps uid 0 to an unprivileged uid. fatal error, unable to load plugins An error occurred while loading or initializing the plugins specified in sudo.conf(5). invalid environment variable name One or more environment variable names specified via the -E option contained an equal sign (=). The arguments to the -E option should be environment variable names without an associated value. no password was provided When tried to read the password, it did not receive any characters. This may happen if no terminal is available (or the -S option is specified) and the standard input has been redirected from /dev/null. a terminal is required to read the password needs to read the password but there is no mechanism available for it to do so. A terminal is not present to read the password from, has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the sudo.conf(5) file or the SUDO_ASKPASS environment variable. no writable temporary directory found sudoedit was unable to find a usable temporary directory in which to store its intermediate files. The no new privileges flag is set, which prevents sudo from running as root. was run by a process that has the Linux no new privileges flag is set. This causes the set-user-ID bit to be ignored when running an executable, which will prevent from functioning. The most likely cause for this is running within a container that sets this flag. Check the documentation to see if it is possible to configure the container such that the flag is not set. sudo must be owned by uid 0 and have the setuid bit set was not run with root privileges. The binary does not have the correct owner or permissions. It must be owned by the root user and have the set-user-ID bit set. sudoedit is not supported on this platform It is only possible to run sudoedit on systems that support setting the effective user-ID. timed out reading password The user did not enter a password before the password timeout (5 minutes by default) expired. you do not exist in the passwd database Your user-ID does not appear in the system passwd database. you may not specify environment variables in edit mode It is only possible to specify environment variables when running a command. When editing a file, the editor is run with the user's environment unmodified. SEE ALSO top su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8) HISTORY top See the HISTORY.md file in the distribution (https://www.sudo.ws/about/history/) for a brief history of sudo. AUTHORS top Many people have worked on over the years; this version consists of code written primarily by: Todd C. Miller See the CONTRIBUTORS.md file in the distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed to . CAVEATS top There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via . Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with the sudoers(5) plugin's noexec functionality. It is not meaningful to run the cd command directly via sudo, e.g., $ sudo cd /usr/local/protected since when the command exits the parent process (your shell) will still be the same. The -D option can be used to run a command in a specific directory. Running shell scripts via can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, set-user-ID shell scripts are generally safe). BUGS top If you believe you have found a bug in , you can submit a bug report at https://bugzilla.sudo.ws/ SUPPORT top Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives. DISCLAIMER top is provided AS IS and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE.md file distributed with or https://www.sudo.ws/about/license/ for complete details. COLOPHON top This page is part of the sudo (execute a command as another user) project. Information about the project can be found at https://www.sudo.ws/. If you have a bug report for this manual page, see https://bugzilla.sudo.ws/. This page was obtained from the project's upstream Git repository https://github.com/sudo-project/sudo on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Sudo 1.9.15p4 August 9, 2023 SUDO(8) Pages that refer to this page: homectl(1), journalctl(1), localectl(1), loginctl(1), machinectl(1), portablectl(1), setpriv(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), uid0(1), userdbctl(1), nsswitch.conf(5), credentials(7), systemd-tmpfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the ownership of "/home/bob" to "root" Bash Command:<START>sudo chown root /home/bob<END>

Change the ownership of "file.sh" to "root"

sudo chown root file.sh

['chown', 'sudo']

Output a Bash command to accomplish the following task. Task: Change the ownership of "file.sh" to "root" Bash Command:<START>sudo chown root file.sh<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n # sudo\n\n> Executes a single command as the superuser or another user.\n> More information: <https://www.sudo.ws/sudo.html>.\n\n- Run a command as the superuser:\n\n`sudo {{less /var/log/syslog}}`\n\n- Edit a file as the superuser with your default editor:\n\n`sudo --edit {{/etc/fstab}}`\n\n- Run a command as another user and/or group:\n\n`sudo --user={{user}} --group={{group}} {{id -a}}`\n\n- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):\n\n`sudo !!`\n\n- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login`\n\n- Launch the default shell with superuser privileges without changing the environment:\n\n`sudo --shell`\n\n- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login --user={{user}}`\n\n- List the allowed (and forbidden) commands for the invoking user:\n\n`sudo --list`\n Task: Change the ownership of "file.sh" to "root" Bash Command:<START>sudo chown root file.sh<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sudo(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sudo(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON SUDO(8) System Manager's Manual SUDO(8) NAME top sudo, sudoedit execute a command as another user SYNOPSIS top sudo -h | -K | -k | -V sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command [arg ...]] sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] [VAR=value] [-i | -s] [command [arg ...]] sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] file ... DESCRIPTION top allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy. supports a plugin architecture for security policies, auditing, and input/output logging. Third parties can develop and distribute their own plugins to work seamlessly with the front- end. The default security policy is sudoers, which is configured via the file /etc/sudoers, or via LDAP. See the Plugins section for more information. The security policy determines what privileges, if any, a user has to run . The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific; the default password prompt timeout for the sudoers security policy is 5 minutes. Security policies may support credential caching to allow the user to run again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running with the -v option, a user can update the cached credentials without running a command. On systems where is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced. When invoked as sudoedit, the -e option (described below), is implied. Security policies and audit plugins may log successful and failed attempts to run . If an I/O plugin is configured, the running command's input and output may be logged as well. The options are as follows: -A, --askpass Normally, if requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example: # Path to askpass helper program Path askpass /usr/X11R6/bin/ssh-askpass If no askpass program is available, will exit with an error. -B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used. -b, --background Run the given command in the background. It is not possible to use shell job control to manipulate background processes started by . Most interactive commands will fail to work properly in background mode. -C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, will close all open file descriptors other than standard input, standard output, and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option. -D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory. -E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment. --preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times. -e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken: 1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used. 3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy: Symbolic links may not be edited (version 1.8.15 and higher). Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher). Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher). Users are never allowed to edit device special files. If the specified file does not exist, it will be created. Unlike most commands run by sudo, the editor is run with the invoking user's environment unmodified. If the temporary file becomes empty after editing, the user will be prompted before it is installed. If, for some reason, is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file. -g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the # character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the # be escaped with a backslash (\). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use. -H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior. -h, --help Display a short help message to the standard output and exit. -h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. The sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host. -i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login- specific resource files such as .profile, .bash_profile, or .login will be read by the shell. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use. -K, --remove-timestamp Similar to the -k option, except that it removes every cached credential for the user, regardless of the terminal or parent process ID. The next time is run, a password must be entered if the security policy requires authentication. It is not possible to use the -K option in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching. -k, --reset-timestamp When used without a command, invalidates the user's cached credentials for the current session. The next time is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with commands run in a different terminal session. See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke permissions from a .logout file. When used in conjunction with a command or an option that may require a password, this option will cause to ignore the user's cached credentials. As a result, will prompt for a password (if one is required by the security policy) and will not update the user's cached credentials. Not all security policies support credential caching. -l, --list If no command is specified, list the privileges for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format. If a command is specified and is permitted by the security policy for the invoking user (or the, user specified by the -U option) on the current host, the fully-qualified path to the command is displayed along with any args. If -l is specified more than once (and the security policy supports it), the matching rule is displayed in a verbose format along with the command. If a command is specified but not allowed by the policy, will exit with a status value of 1. -N, --no-update Do not update the user's cached credentials, even if the user successfully authenticates. Unlike the -k flag, existing cached credentials are used if they are valid. To detect when the user's cached credentials are valid (or when no authentication is required), the following can be used: sudo -Nnv Not all security policies support credential caching. -n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, will display an error message and exit. -P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user. -p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent (%) escape sequences are supported by the sudoers policy: %H expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in sudoers(5)) %h expanded to the local host name without the domain name %p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5)) %U expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified) %u expanded to the invoking user's login name %% two consecutive % characters are collapsed into a single % character The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers. -R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory. -S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device. -s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. -U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. When using the sudoers policy, the -U option is restricted to the root user and users with either the list priviege for the specified user or the ability to run any command as root or user on the current host. -T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the user's ability to set timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled. -u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the # character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the # be escaped with a backslash (\). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this. -V, --version Print the version string as well as the version string of any configured plugins. If the invoking user is already root, the -V option will display the options passed to configure when was built; plugins may display additional information such as default options. -v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials. -- The -- is used to delimit the end of the options. Subsequent options are passed to the command. Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input. Environment variables to be set for the command may also be passed as options to in the form VAR=value, for example LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be subject to restrictions imposed by the security policy plugin. The sudoers policy subjects environment variables passed as options to the same restrictions as existing environment variables with one important difference. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information. COMMAND EXECUTION top When executes a command, the security policy specifies the execution environment for the command. Typically, the real and effective user and group and IDs are set to match those of the target user, as specified in the password database, and the group vector is initialized based on the group database (unless the -P option was specified). The following parameters may be specified by security policy: real and effective user-ID real and effective group-ID supplementary group-IDs the environment list current working directory file creation mode mask (umask) scheduling priority (aka nice value) Process model There are two distinct ways can run a command. If an I/O logging plugin is configured to log terminal I/O, or if the security policy explicitly requests it, a new pseudo-terminal (pty) is allocated and fork(2) is used to create a second process, referred to as the monitor. The monitor creates a new terminal session with itself as the leader and the pty as its controlling terminal, calls fork(2) again, sets up the execution environment as described above, and then uses the execve(2) system call to run the command in the child process. The monitor exists to relay job control signals between the user's terminal and the pty the command is being run in. This makes it possible to suspend and resume the command normally. Without the monitor, the command would be in what POSIX terms an orphaned process group and it would not receive any job control signals from the kernel. When the command exits or is terminated by a signal, the monitor passes the command's exit status to the main process and exits. After receiving the command's exit status, the main process passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugin, and exits. This mode is the default for sudo versions 1.9.14 and above when using the sudoers policy. If no pty is used, calls fork(2), sets up the execution environment as described above, and uses the execve(2) system call to run the command in the child process. The main process waits until the command has completed, then passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugins, and exits. As a special case, if the policy plugin does not define a close function, will execute the command directly instead of calling fork(2) first. The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled. Both pam_session and pam_setcred are enabled by default on systems using PAM. This mode is the default for sudo versions prior to 1.9.14 when using the sudoers policy. On systems that use PAM, the security policy's close function is responsible for closing the PAM session. It may also log the command's exit status. Signal handling When the command is run as a child of the process, will relay signals it receives to the command. The SIGINT and SIGQUIT signals are only relayed when the command is being run in a new pty or when the signal was sent by a user process, not the kernel. This prevents the command from receiving SIGINT twice each time the user enters control-C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by . As a special case, will not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) utility sends SIGTERM to all non-system processes other than itself before rebooting the system. This prevents from relaying the SIGTERM signal it received back to reboot(8), which might then exit before the system was actually rebooted, leaving it in a half-dead state similar to single user mode. Note, however, that this check only applies to the command run by and not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via may cause the system to end up in this undefined state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the command and the calling process). Plugins Plugins may be specified via Plugin directives in the sudo.conf(5) file. They may be loaded as dynamic shared objects (on systems that support them), or compiled directly into the binary. If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, will use sudoers(5) for the policy, auditing, and I/O logging plugins. See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for more information about the plugin architecture. EXIT VALUE top Upon successful execution of a command, the exit status from will be the exit status of the program that was executed. If the command terminated due to receipt of a signal, will send itself the same signal that terminated the command. If the -l option was specified without a command, will exit with a value of 0 if the user is allowed to run and they authenticated successfully (as required by the security policy). If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by the security policy, otherwise it will be 1. If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, exits with a value of 1. In the latter case, the error string is printed to the standard error. If cannot stat(2) one or more entries in the user's PATH, an error is printed to the standard error. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat(2) to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. SECURITY NOTES top tries to be safe when executing external commands. To prevent command spoofing, checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the program that executes. Users should never be granted privileges to execute files that are writable by the user or that reside in a directory that is writable by the user. If the user can modify or replace the command there is no way to limit what additional commands they can run. By default, will only log the command it explicitly runs. If a user runs a command such as sudo su or sudo sh, subsequent commands run from that shell are not subject to sudo's security policy. The same is true for commands that offer shell escapes (including most editors). If I/O logging is enabled, subsequent commands will have their input and/or output logged, but there will not be traditional logs for those commands. Because of this, care must be taken when giving users access to commands via to verify that the command does not inadvertently give the user an effective root shell. For information on ways to address this, see the Preventing shell escapes section in sudoers(5). To prevent the disclosure of potentially sensitive information, disables core dumps by default while it is executing (they are re-enabled for the command that is run). This historical practice dates from a time when most operating systems allowed set-user-ID processes to dump core by default. To aid in debugging crashes, you may wish to re-enable core dumps by setting disable_coredump to false in the sudo.conf(5) file as follows: Set disable_coredump false See the sudo.conf(5) manual for more information. ENVIRONMENT top utilizes the following environment variables. The security policy has control over the actual content of the command's environment. EDITOR Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set. MAIL Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is present in the env_keep list). HOME Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the env_keep list. LOGNAME Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list). PATH May be overridden by the security policy. SHELL Used to determine shell to run with -s option. SUDO_ASKPASS Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified. SUDO_COMMAND Set to the command run by sudo, including any args. The args are truncated at 4096 characters to prevent a potential execution error. SUDO_EDITOR Default editor to use in -e (sudoedit) mode. SUDO_GID Set to the group-ID of the user who invoked sudo. SUDO_PROMPT Used as the default password prompt unless the -p option was specified. SUDO_PS1 If set, PS1 will be set to its value for the program being run. SUDO_UID Set to the user-ID of the user who invoked sudo. SUDO_USER Set to the login name of the user who invoked sudo. USER Set to the same value as LOGNAME, described above. VISUAL Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set. FILES top /etc/sudo.conf front-end configuration EXAMPLES top The following examples assume a properly configured security policy. To get a file listing of an unreadable directory: $ sudo ls /usr/local/protected To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root: $ sudo -u yaz ls ~yaz To edit the index.html file as user www: $ sudoedit -u www ~www/htdocs/index.html To view system logs only accessible to root and users in the adm group: $ sudo -g adm more /var/log/syslog To run an editor as jim with a different primary group: $ sudoedit -u jim -g audio ~jim/sound.txt To shut down a machine: $ sudo shutdown -r +15 "quick reboot" To make a usage listing of the directories in the /home partition. The commands are run in a sub-shell to allow the cd command and file redirection to work. $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" DIAGNOSTICS top Error messages produced by include: editing files in a writable directory is not permitted By default, sudoedit does not permit editing a file when any of the parent directories are writable by the invoking user. This avoids a race condition that could allow the user to overwrite an arbitrary file. See the sudoedit_checkdir option in sudoers(5) for more information. editing symbolic links is not permitted By default, sudoedit does not follow symbolic links when opening files. See the sudoedit_follow option in sudoers(5) for more information. effective uid is not 0, is sudo installed setuid root? was not run with root privileges. The binary must be owned by the root user and have the set-user-ID bit set. Also, it must not be located on a file system mounted with the nosuid option or on an NFS file system that maps uid 0 to an unprivileged uid. effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges? was not run with root privileges. The binary has the proper owner and permissions but it still did not run with root privileges. The most common reason for this is that the file system the binary is located on is mounted with the nosuid option or it is an NFS file system that maps uid 0 to an unprivileged uid. fatal error, unable to load plugins An error occurred while loading or initializing the plugins specified in sudo.conf(5). invalid environment variable name One or more environment variable names specified via the -E option contained an equal sign (=). The arguments to the -E option should be environment variable names without an associated value. no password was provided When tried to read the password, it did not receive any characters. This may happen if no terminal is available (or the -S option is specified) and the standard input has been redirected from /dev/null. a terminal is required to read the password needs to read the password but there is no mechanism available for it to do so. A terminal is not present to read the password from, has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the sudo.conf(5) file or the SUDO_ASKPASS environment variable. no writable temporary directory found sudoedit was unable to find a usable temporary directory in which to store its intermediate files. The no new privileges flag is set, which prevents sudo from running as root. was run by a process that has the Linux no new privileges flag is set. This causes the set-user-ID bit to be ignored when running an executable, which will prevent from functioning. The most likely cause for this is running within a container that sets this flag. Check the documentation to see if it is possible to configure the container such that the flag is not set. sudo must be owned by uid 0 and have the setuid bit set was not run with root privileges. The binary does not have the correct owner or permissions. It must be owned by the root user and have the set-user-ID bit set. sudoedit is not supported on this platform It is only possible to run sudoedit on systems that support setting the effective user-ID. timed out reading password The user did not enter a password before the password timeout (5 minutes by default) expired. you do not exist in the passwd database Your user-ID does not appear in the system passwd database. you may not specify environment variables in edit mode It is only possible to specify environment variables when running a command. When editing a file, the editor is run with the user's environment unmodified. SEE ALSO top su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8) HISTORY top See the HISTORY.md file in the distribution (https://www.sudo.ws/about/history/) for a brief history of sudo. AUTHORS top Many people have worked on over the years; this version consists of code written primarily by: Todd C. Miller See the CONTRIBUTORS.md file in the distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed to . CAVEATS top There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via . Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with the sudoers(5) plugin's noexec functionality. It is not meaningful to run the cd command directly via sudo, e.g., $ sudo cd /usr/local/protected since when the command exits the parent process (your shell) will still be the same. The -D option can be used to run a command in a specific directory. Running shell scripts via can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, set-user-ID shell scripts are generally safe). BUGS top If you believe you have found a bug in , you can submit a bug report at https://bugzilla.sudo.ws/ SUPPORT top Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives. DISCLAIMER top is provided AS IS and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE.md file distributed with or https://www.sudo.ws/about/license/ for complete details. COLOPHON top This page is part of the sudo (execute a command as another user) project. Information about the project can be found at https://www.sudo.ws/. If you have a bug report for this manual page, see https://bugzilla.sudo.ws/. This page was obtained from the project's upstream Git repository https://github.com/sudo-project/sudo on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Sudo 1.9.15p4 August 9, 2023 SUDO(8) Pages that refer to this page: homectl(1), journalctl(1), localectl(1), loginctl(1), machinectl(1), portablectl(1), setpriv(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), uid0(1), userdbctl(1), nsswitch.conf(5), credentials(7), systemd-tmpfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the ownership of "file.sh" to "root" Bash Command:<START>sudo chown root file.sh<END>

Change the ownership of all aluno1's files in the current directory and below to aluno2

find . -user aluno1 -exec chown aluno2 {}

['find', 'chown']

Output a Bash command to accomplish the following task. Task: Change the ownership of all aluno1's files in the current directory and below to aluno2 Bash Command:<START>find . -user aluno1 -exec chown aluno2 {}<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the ownership of all aluno1's files in the current directory and below to aluno2 Bash Command:<START>find . -user aluno1 -exec chown aluno2 {}<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the ownership of all aluno1's files in the current directory and below to aluno2 Bash Command:<START>find . -user aluno1 -exec chown aluno2 {}<END>

Change the ownership of all files in the current directory tree from root to www-data

find -user root -exec chown www-data {} \;

['find', 'chown']

Output a Bash command to accomplish the following task. Task: Change the ownership of all files in the current directory tree from root to www-data Bash Command:<START>find -user root -exec chown www-data {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the ownership of all files in the current directory tree from root to www-data Bash Command:<START>find -user root -exec chown www-data {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the ownership of all files in the current directory tree from root to www-data Bash Command:<START>find -user root -exec chown www-data {} \;<END>

Change the ownership of all files in the current directory tree to myuser:a-common-group-name

find . -exec chown myuser:a-common-group-name {} +

['find', 'chown']

Output a Bash command to accomplish the following task. Task: Change the ownership of all files in the current directory tree to myuser:a-common-group-name Bash Command:<START>find . -exec chown myuser:a-common-group-name {} +<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the ownership of all files in the current directory tree to myuser:a-common-group-name Bash Command:<START>find . -exec chown myuser:a-common-group-name {} +<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the ownership of all files in the current directory tree to myuser:a-common-group-name Bash Command:<START>find . -exec chown myuser:a-common-group-name {} +<END>

Change the ownership to eva for all files/directories that belong to the user 'george' in the entire file system without traversing to other devices/partitions

find -x / -user george -print0 | xargs -0 chown eva

['find', 'xargs', 'chown']

Output a Bash command to accomplish the following task. Task: Change the ownership to eva for all files/directories that belong to the user 'george' in the entire file system without traversing to other devices/partitions Bash Command:<START>find -x / -user george -print0 | xargs -0 chown eva<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the ownership to eva for all files/directories that belong to the user 'george' in the entire file system without traversing to other devices/partitions Bash Command:<START>find -x / -user george -print0 | xargs -0 chown eva<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the ownership to eva for all files/directories that belong to the user 'george' in the entire file system without traversing to other devices/partitions Bash Command:<START>find -x / -user george -print0 | xargs -0 chown eva<END>

Change the ownership to the user daisy for all directories under current directory that are owned by harry

find . -type d -user harry -exec chown daisy {} \;

['find', 'chown']

Output a Bash command to accomplish the following task. Task: Change the ownership to the user daisy for all directories under current directory that are owned by harry Bash Command:<START>find . -type d -user harry -exec chown daisy {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the ownership to the user daisy for all directories under current directory that are owned by harry Bash Command:<START>find . -type d -user harry -exec chown daisy {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the ownership to the user daisy for all directories under current directory that are owned by harry Bash Command:<START>find . -type d -user harry -exec chown daisy {} \;<END>

Change the permission of all regular files under current directory tree to 644

find . -type f -exec chmod 644 {} \;

['find', 'chmod']

Output a Bash command to accomplish the following task. Task: Change the permission of all regular files under current directory tree to 644 Bash Command:<START>find . -type f -exec chmod 644 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chmod\n\n> Change the access permissions of a file or directory.\n> More information: <https://www.gnu.org/software/coreutils/chmod>.\n\n- Give the [u]ser who owns a file the right to e[x]ecute it:\n\n`chmod u+x {{path/to/file}}`\n\n- Give the [u]ser rights to [r]ead and [w]rite to a file/directory:\n\n`chmod u+rw {{path/to/file_or_directory}}`\n\n- Remove e[x]ecutable rights from the [g]roup:\n\n`chmod g-x {{path/to/file}}`\n\n- Give [a]ll users rights to [r]ead and e[x]ecute:\n\n`chmod a+rx {{path/to/file}}`\n\n- Give [o]thers (not in the file owner's group) the same rights as the [g]roup:\n\n`chmod o=g {{path/to/file}}`\n\n- Remove all rights from [o]thers:\n\n`chmod o= {{path/to/file}}`\n\n- Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:\n\n`chmod -R g+w,o+w {{path/to/directory}}`\n\n- Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:\n\n`chmod -R a+rX {{path/to/directory}}`\n Task: Change the permission of all regular files under current directory tree to 644 Bash Command:<START>find . -type f -exec chmod 644 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chmod(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chmod(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHMOD(1) User Commands CHMOD(1) NAME top chmod - change file mode bits SYNOPSIS top chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits. The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple symbolic modes can be given, separated by commas. A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users (a). If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected. The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these letters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values. chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links encountered during recursive directory traversals. SETUID AND SETGID BITS top chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. For directories chmod preserves set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s. To clear these bits for directories with a numeric mode requires an additional leading zero like 00755, leading minus like -6000, or leading equals like =755. RESTRICTED DELETION FLAG OR STICKY BIT top The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; this is called the sticky bit. OPTIONS top Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's mode instead of specifying MODE values. RFILE is always dereferenced if a symbolic link. -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(2) Full documentation <https://www.gnu.org/software/coreutils/chmod> or available locally via: info '(coreutils) chmod invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHMOD(1) Pages that refer to this page: bash(1), chacl(1), find(1), nfs4_setfacl(1), rsync(1), setfacl(1), chmod(2), fcntl(2), lp(4), rsyncd.conf(5), path_resolution(7), symlink(7), xattr(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the permission of all regular files under current directory tree to 644 Bash Command:<START>find . -type f -exec chmod 644 {} \;<END>

Change the permission to 0644 for all files under current directory

find . -type f -exec chmod 0644 {} +

['find', 'chmod']

Output a Bash command to accomplish the following task. Task: Change the permission to 0644 for all files under current directory Bash Command:<START>find . -type f -exec chmod 0644 {} +<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chmod\n\n> Change the access permissions of a file or directory.\n> More information: <https://www.gnu.org/software/coreutils/chmod>.\n\n- Give the [u]ser who owns a file the right to e[x]ecute it:\n\n`chmod u+x {{path/to/file}}`\n\n- Give the [u]ser rights to [r]ead and [w]rite to a file/directory:\n\n`chmod u+rw {{path/to/file_or_directory}}`\n\n- Remove e[x]ecutable rights from the [g]roup:\n\n`chmod g-x {{path/to/file}}`\n\n- Give [a]ll users rights to [r]ead and e[x]ecute:\n\n`chmod a+rx {{path/to/file}}`\n\n- Give [o]thers (not in the file owner's group) the same rights as the [g]roup:\n\n`chmod o=g {{path/to/file}}`\n\n- Remove all rights from [o]thers:\n\n`chmod o= {{path/to/file}}`\n\n- Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:\n\n`chmod -R g+w,o+w {{path/to/directory}}`\n\n- Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:\n\n`chmod -R a+rX {{path/to/directory}}`\n Task: Change the permission to 0644 for all files under current directory Bash Command:<START>find . -type f -exec chmod 0644 {} +<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chmod(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chmod(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHMOD(1) User Commands CHMOD(1) NAME top chmod - change file mode bits SYNOPSIS top chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits. The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple symbolic modes can be given, separated by commas. A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users (a). If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected. The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these letters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values. chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links encountered during recursive directory traversals. SETUID AND SETGID BITS top chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. For directories chmod preserves set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s. To clear these bits for directories with a numeric mode requires an additional leading zero like 00755, leading minus like -6000, or leading equals like =755. RESTRICTED DELETION FLAG OR STICKY BIT top The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; this is called the sticky bit. OPTIONS top Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's mode instead of specifying MODE values. RFILE is always dereferenced if a symbolic link. -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(2) Full documentation <https://www.gnu.org/software/coreutils/chmod> or available locally via: info '(coreutils) chmod invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHMOD(1) Pages that refer to this page: bash(1), chacl(1), find(1), nfs4_setfacl(1), rsync(1), setfacl(1), chmod(2), fcntl(2), lp(4), rsyncd.conf(5), path_resolution(7), symlink(7), xattr(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the permission to 0644 for all files under current directory Bash Command:<START>find . -type f -exec chmod 0644 {} +<END>

Change the permission to 0644 for all files under current directory

find . -type f -exec chmod 0644 {} \;

['find', 'chmod']

Output a Bash command to accomplish the following task. Task: Change the permission to 0644 for all files under current directory Bash Command:<START>find . -type f -exec chmod 0644 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chmod\n\n> Change the access permissions of a file or directory.\n> More information: <https://www.gnu.org/software/coreutils/chmod>.\n\n- Give the [u]ser who owns a file the right to e[x]ecute it:\n\n`chmod u+x {{path/to/file}}`\n\n- Give the [u]ser rights to [r]ead and [w]rite to a file/directory:\n\n`chmod u+rw {{path/to/file_or_directory}}`\n\n- Remove e[x]ecutable rights from the [g]roup:\n\n`chmod g-x {{path/to/file}}`\n\n- Give [a]ll users rights to [r]ead and e[x]ecute:\n\n`chmod a+rx {{path/to/file}}`\n\n- Give [o]thers (not in the file owner's group) the same rights as the [g]roup:\n\n`chmod o=g {{path/to/file}}`\n\n- Remove all rights from [o]thers:\n\n`chmod o= {{path/to/file}}`\n\n- Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:\n\n`chmod -R g+w,o+w {{path/to/directory}}`\n\n- Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:\n\n`chmod -R a+rX {{path/to/directory}}`\n Task: Change the permission to 0644 for all files under current directory Bash Command:<START>find . -type f -exec chmod 0644 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chmod(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chmod(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHMOD(1) User Commands CHMOD(1) NAME top chmod - change file mode bits SYNOPSIS top chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits. The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple symbolic modes can be given, separated by commas. A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users (a). If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected. The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these letters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values. chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links encountered during recursive directory traversals. SETUID AND SETGID BITS top chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. For directories chmod preserves set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s. To clear these bits for directories with a numeric mode requires an additional leading zero like 00755, leading minus like -6000, or leading equals like =755. RESTRICTED DELETION FLAG OR STICKY BIT top The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; this is called the sticky bit. OPTIONS top Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's mode instead of specifying MODE values. RFILE is always dereferenced if a symbolic link. -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(2) Full documentation <https://www.gnu.org/software/coreutils/chmod> or available locally via: info '(coreutils) chmod invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHMOD(1) Pages that refer to this page: bash(1), chacl(1), find(1), nfs4_setfacl(1), rsync(1), setfacl(1), chmod(2), fcntl(2), lp(4), rsyncd.conf(5), path_resolution(7), symlink(7), xattr(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the permission to 0644 for all files under current directory Bash Command:<START>find . -type f -exec chmod 0644 {} \;<END>

Change the permission to 0755 for all directories under current directory

find . -type d -exec chmod 0755 {} \;

['find', 'chmod']

Output a Bash command to accomplish the following task. Task: Change the permission to 0755 for all directories under current directory Bash Command:<START>find . -type d -exec chmod 0755 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chmod\n\n> Change the access permissions of a file or directory.\n> More information: <https://www.gnu.org/software/coreutils/chmod>.\n\n- Give the [u]ser who owns a file the right to e[x]ecute it:\n\n`chmod u+x {{path/to/file}}`\n\n- Give the [u]ser rights to [r]ead and [w]rite to a file/directory:\n\n`chmod u+rw {{path/to/file_or_directory}}`\n\n- Remove e[x]ecutable rights from the [g]roup:\n\n`chmod g-x {{path/to/file}}`\n\n- Give [a]ll users rights to [r]ead and e[x]ecute:\n\n`chmod a+rx {{path/to/file}}`\n\n- Give [o]thers (not in the file owner's group) the same rights as the [g]roup:\n\n`chmod o=g {{path/to/file}}`\n\n- Remove all rights from [o]thers:\n\n`chmod o= {{path/to/file}}`\n\n- Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:\n\n`chmod -R g+w,o+w {{path/to/directory}}`\n\n- Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:\n\n`chmod -R a+rX {{path/to/directory}}`\n Task: Change the permission to 0755 for all directories under current directory Bash Command:<START>find . -type d -exec chmod 0755 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chmod(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chmod(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHMOD(1) User Commands CHMOD(1) NAME top chmod - change file mode bits SYNOPSIS top chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits. The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple symbolic modes can be given, separated by commas. A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users (a). If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected. The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these letters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values. chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links encountered during recursive directory traversals. SETUID AND SETGID BITS top chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. For directories chmod preserves set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s. To clear these bits for directories with a numeric mode requires an additional leading zero like 00755, leading minus like -6000, or leading equals like =755. RESTRICTED DELETION FLAG OR STICKY BIT top The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; this is called the sticky bit. OPTIONS top Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's mode instead of specifying MODE values. RFILE is always dereferenced if a symbolic link. -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(2) Full documentation <https://www.gnu.org/software/coreutils/chmod> or available locally via: info '(coreutils) chmod invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHMOD(1) Pages that refer to this page: bash(1), chacl(1), find(1), nfs4_setfacl(1), rsync(1), setfacl(1), chmod(2), fcntl(2), lp(4), rsyncd.conf(5), path_resolution(7), symlink(7), xattr(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the permission to 0755 for all directories under current directory Bash Command:<START>find . -type d -exec chmod 0755 {} \;<END>

Change the permission to 644 for all files under current directory

find . -type f | xargs -I{} chmod -v 644 {}

['find', 'xargs', 'chmod']

Output a Bash command to accomplish the following task. Task: Change the permission to 644 for all files under current directory Bash Command:<START>find . -type f | xargs -I{} chmod -v 644 {}<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # chmod\n\n> Change the access permissions of a file or directory.\n> More information: <https://www.gnu.org/software/coreutils/chmod>.\n\n- Give the [u]ser who owns a file the right to e[x]ecute it:\n\n`chmod u+x {{path/to/file}}`\n\n- Give the [u]ser rights to [r]ead and [w]rite to a file/directory:\n\n`chmod u+rw {{path/to/file_or_directory}}`\n\n- Remove e[x]ecutable rights from the [g]roup:\n\n`chmod g-x {{path/to/file}}`\n\n- Give [a]ll users rights to [r]ead and e[x]ecute:\n\n`chmod a+rx {{path/to/file}}`\n\n- Give [o]thers (not in the file owner's group) the same rights as the [g]roup:\n\n`chmod o=g {{path/to/file}}`\n\n- Remove all rights from [o]thers:\n\n`chmod o= {{path/to/file}}`\n\n- Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:\n\n`chmod -R g+w,o+w {{path/to/directory}}`\n\n- Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:\n\n`chmod -R a+rX {{path/to/directory}}`\n Task: Change the permission to 644 for all files under current directory Bash Command:<START>find . -type f | xargs -I{} chmod -v 644 {}<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chmod(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chmod(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHMOD(1) User Commands CHMOD(1) NAME top chmod - change file mode bits SYNOPSIS top chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits. The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple symbolic modes can be given, separated by commas. A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users (a). If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected. The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these letters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values. chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links encountered during recursive directory traversals. SETUID AND SETGID BITS top chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. For directories chmod preserves set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s. To clear these bits for directories with a numeric mode requires an additional leading zero like 00755, leading minus like -6000, or leading equals like =755. RESTRICTED DELETION FLAG OR STICKY BIT top The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; this is called the sticky bit. OPTIONS top Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's mode instead of specifying MODE values. RFILE is always dereferenced if a symbolic link. -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(2) Full documentation <https://www.gnu.org/software/coreutils/chmod> or available locally via: info '(coreutils) chmod invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHMOD(1) Pages that refer to this page: bash(1), chacl(1), find(1), nfs4_setfacl(1), rsync(1), setfacl(1), chmod(2), fcntl(2), lp(4), rsyncd.conf(5), path_resolution(7), symlink(7), xattr(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the permission to 644 for all files under current directory Bash Command:<START>find . -type f | xargs -I{} chmod -v 644 {}<END>

Change the permission to 644 for all files under current directory

find . -type f | xargs chmod -v 644

['find', 'xargs', 'chmod']

Output a Bash command to accomplish the following task. Task: Change the permission to 644 for all files under current directory Bash Command:<START>find . -type f | xargs chmod -v 644<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # chmod\n\n> Change the access permissions of a file or directory.\n> More information: <https://www.gnu.org/software/coreutils/chmod>.\n\n- Give the [u]ser who owns a file the right to e[x]ecute it:\n\n`chmod u+x {{path/to/file}}`\n\n- Give the [u]ser rights to [r]ead and [w]rite to a file/directory:\n\n`chmod u+rw {{path/to/file_or_directory}}`\n\n- Remove e[x]ecutable rights from the [g]roup:\n\n`chmod g-x {{path/to/file}}`\n\n- Give [a]ll users rights to [r]ead and e[x]ecute:\n\n`chmod a+rx {{path/to/file}}`\n\n- Give [o]thers (not in the file owner's group) the same rights as the [g]roup:\n\n`chmod o=g {{path/to/file}}`\n\n- Remove all rights from [o]thers:\n\n`chmod o= {{path/to/file}}`\n\n- Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:\n\n`chmod -R g+w,o+w {{path/to/directory}}`\n\n- Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:\n\n`chmod -R a+rX {{path/to/directory}}`\n Task: Change the permission to 644 for all files under current directory Bash Command:<START>find . -type f | xargs chmod -v 644<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chmod(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chmod(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHMOD(1) User Commands CHMOD(1) NAME top chmod - change file mode bits SYNOPSIS top chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits. The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple symbolic modes can be given, separated by commas. A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users (a). If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected. The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these letters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values. chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links encountered during recursive directory traversals. SETUID AND SETGID BITS top chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. For directories chmod preserves set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s. To clear these bits for directories with a numeric mode requires an additional leading zero like 00755, leading minus like -6000, or leading equals like =755. RESTRICTED DELETION FLAG OR STICKY BIT top The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; this is called the sticky bit. OPTIONS top Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's mode instead of specifying MODE values. RFILE is always dereferenced if a symbolic link. -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(2) Full documentation <https://www.gnu.org/software/coreutils/chmod> or available locally via: info '(coreutils) chmod invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHMOD(1) Pages that refer to this page: bash(1), chacl(1), find(1), nfs4_setfacl(1), rsync(1), setfacl(1), chmod(2), fcntl(2), lp(4), rsyncd.conf(5), path_resolution(7), symlink(7), xattr(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the permission to 644 for all files under current directory Bash Command:<START>find . -type f | xargs chmod -v 644<END>

Change the permission to 755 for all directories under current directory

find . -type d | xargs chmod -v 755

['find', 'xargs', 'chmod']

Output a Bash command to accomplish the following task. Task: Change the permission to 755 for all directories under current directory Bash Command:<START>find . -type d | xargs chmod -v 755<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # chmod\n\n> Change the access permissions of a file or directory.\n> More information: <https://www.gnu.org/software/coreutils/chmod>.\n\n- Give the [u]ser who owns a file the right to e[x]ecute it:\n\n`chmod u+x {{path/to/file}}`\n\n- Give the [u]ser rights to [r]ead and [w]rite to a file/directory:\n\n`chmod u+rw {{path/to/file_or_directory}}`\n\n- Remove e[x]ecutable rights from the [g]roup:\n\n`chmod g-x {{path/to/file}}`\n\n- Give [a]ll users rights to [r]ead and e[x]ecute:\n\n`chmod a+rx {{path/to/file}}`\n\n- Give [o]thers (not in the file owner's group) the same rights as the [g]roup:\n\n`chmod o=g {{path/to/file}}`\n\n- Remove all rights from [o]thers:\n\n`chmod o= {{path/to/file}}`\n\n- Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:\n\n`chmod -R g+w,o+w {{path/to/directory}}`\n\n- Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:\n\n`chmod -R a+rX {{path/to/directory}}`\n Task: Change the permission to 755 for all directories under current directory Bash Command:<START>find . -type d | xargs chmod -v 755<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chmod(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chmod(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHMOD(1) User Commands CHMOD(1) NAME top chmod - change file mode bits SYNOPSIS top chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits. The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple symbolic modes can be given, separated by commas. A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users (a). If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected. The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these letters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values. chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links encountered during recursive directory traversals. SETUID AND SETGID BITS top chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. For directories chmod preserves set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s. To clear these bits for directories with a numeric mode requires an additional leading zero like 00755, leading minus like -6000, or leading equals like =755. RESTRICTED DELETION FLAG OR STICKY BIT top The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; this is called the sticky bit. OPTIONS top Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's mode instead of specifying MODE values. RFILE is always dereferenced if a symbolic link. -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(2) Full documentation <https://www.gnu.org/software/coreutils/chmod> or available locally via: info '(coreutils) chmod invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHMOD(1) Pages that refer to this page: bash(1), chacl(1), find(1), nfs4_setfacl(1), rsync(1), setfacl(1), chmod(2), fcntl(2), lp(4), rsyncd.conf(5), path_resolution(7), symlink(7), xattr(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the permission to 755 for all directories under current directory Bash Command:<START>find . -type d | xargs chmod -v 755<END>

Change the permissions of all regular files whose names end with .mp3 in the directory tree /var/ftp/mp3

find /var/ftp/mp3 -name '*.mp3' -type f -exec chmod 644 {} \;

['find', 'chmod']

Output a Bash command to accomplish the following task. Task: Change the permissions of all regular files whose names end with .mp3 in the directory tree /var/ftp/mp3 Bash Command:<START>find /var/ftp/mp3 -name '*.mp3' -type f -exec chmod 644 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chmod\n\n> Change the access permissions of a file or directory.\n> More information: <https://www.gnu.org/software/coreutils/chmod>.\n\n- Give the [u]ser who owns a file the right to e[x]ecute it:\n\n`chmod u+x {{path/to/file}}`\n\n- Give the [u]ser rights to [r]ead and [w]rite to a file/directory:\n\n`chmod u+rw {{path/to/file_or_directory}}`\n\n- Remove e[x]ecutable rights from the [g]roup:\n\n`chmod g-x {{path/to/file}}`\n\n- Give [a]ll users rights to [r]ead and e[x]ecute:\n\n`chmod a+rx {{path/to/file}}`\n\n- Give [o]thers (not in the file owner's group) the same rights as the [g]roup:\n\n`chmod o=g {{path/to/file}}`\n\n- Remove all rights from [o]thers:\n\n`chmod o= {{path/to/file}}`\n\n- Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:\n\n`chmod -R g+w,o+w {{path/to/directory}}`\n\n- Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:\n\n`chmod -R a+rX {{path/to/directory}}`\n Task: Change the permissions of all regular files whose names end with .mp3 in the directory tree /var/ftp/mp3 Bash Command:<START>find /var/ftp/mp3 -name '*.mp3' -type f -exec chmod 644 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chmod(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chmod(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHMOD(1) User Commands CHMOD(1) NAME top chmod - change file mode bits SYNOPSIS top chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits. The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple symbolic modes can be given, separated by commas. A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users (a). If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected. The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these letters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values. chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links encountered during recursive directory traversals. SETUID AND SETGID BITS top chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. For directories chmod preserves set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s. To clear these bits for directories with a numeric mode requires an additional leading zero like 00755, leading minus like -6000, or leading equals like =755. RESTRICTED DELETION FLAG OR STICKY BIT top The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; this is called the sticky bit. OPTIONS top Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's mode instead of specifying MODE values. RFILE is always dereferenced if a symbolic link. -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(2) Full documentation <https://www.gnu.org/software/coreutils/chmod> or available locally via: info '(coreutils) chmod invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHMOD(1) Pages that refer to this page: bash(1), chacl(1), find(1), nfs4_setfacl(1), rsync(1), setfacl(1), chmod(2), fcntl(2), lp(4), rsyncd.conf(5), path_resolution(7), symlink(7), xattr(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the permissions of all regular files whose names end with .mp3 in the directory tree /var/ftp/mp3 Bash Command:<START>find /var/ftp/mp3 -name '*.mp3' -type f -exec chmod 644 {} \;<END>

Change the permissions of the current directory and all its subdirectories to 755.

find . -type d -exec chmod 755 {} \;

['find', 'chmod']

Output a Bash command to accomplish the following task. Task: Change the permissions of the current directory and all its subdirectories to 755. Bash Command:<START>find . -type d -exec chmod 755 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chmod\n\n> Change the access permissions of a file or directory.\n> More information: <https://www.gnu.org/software/coreutils/chmod>.\n\n- Give the [u]ser who owns a file the right to e[x]ecute it:\n\n`chmod u+x {{path/to/file}}`\n\n- Give the [u]ser rights to [r]ead and [w]rite to a file/directory:\n\n`chmod u+rw {{path/to/file_or_directory}}`\n\n- Remove e[x]ecutable rights from the [g]roup:\n\n`chmod g-x {{path/to/file}}`\n\n- Give [a]ll users rights to [r]ead and e[x]ecute:\n\n`chmod a+rx {{path/to/file}}`\n\n- Give [o]thers (not in the file owner's group) the same rights as the [g]roup:\n\n`chmod o=g {{path/to/file}}`\n\n- Remove all rights from [o]thers:\n\n`chmod o= {{path/to/file}}`\n\n- Change permissions recursively giving [g]roup and [o]thers the ability to [w]rite:\n\n`chmod -R g+w,o+w {{path/to/directory}}`\n\n- Recursively give [a]ll users [r]ead permissions to files and e[X]ecute permissions to sub-directories within a directory:\n\n`chmod -R a+rX {{path/to/directory}}`\n Task: Change the permissions of the current directory and all its subdirectories to 755. Bash Command:<START>find . -type d -exec chmod 755 {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chmod(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chmod(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | SETUID AND SETGID BITS | RESTRICTED DELETION FLAG OR STICKY BIT | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHMOD(1) User Commands CHMOD(1) NAME top chmod - change file mode bits SYNOPSIS top chmod [OPTION]... MODE[,MODE]... FILE... chmod [OPTION]... OCTAL-MODE FILE... chmod [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits. The format of a symbolic mode is [ugoa...][[-+=][perms...]...], where perms is either zero or more letters from the set rwxXst, or a single letter from the set ugo. Multiple symbolic modes can be given, separated by commas. A combination of the letters ugoa controls which users' access to the file will be changed: the user who owns it (u), other users in the file's group (g), other users not in the file's group (o), or all users (a). If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected. The operator + causes the selected file mode bits to be added to the existing file mode bits of each file; - causes them to be removed; and = causes them to be added and causes unmentioned bits to be removed except that a directory's unmentioned set user and group ID bits are not affected. The letters rwxXst select file mode bits for the affected users: read (r), write (w), execute (or search for directories) (x), execute/search only if the file is a directory or already has execute permission for some user (X), set user or group ID on execution (s), restricted deletion flag or sticky bit (t). Instead of one or more of these letters, you can specify exactly one of the letters ugo: the permissions granted to the user who owns the file (u), the permissions granted to other users who are members of the file's group (g), and the permissions granted to users that are in neither of the two preceding categories (o). A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and restricted deletion or sticky (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissions for other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values. chmod never changes the permissions of symbolic links; the chmod system call cannot change their permissions. This is not a problem since the permissions of symbolic links are never used. However, for each symbolic link listed on the command line, chmod changes the permissions of the pointed-to file. In contrast, chmod ignores symbolic links encountered during recursive directory traversals. SETUID AND SETGID BITS top chmod clears the set-group-ID bit of a regular file if the file's group ID does not match the user's effective group ID or one of the user's supplementary group IDs, unless the user has appropriate privileges. Additional restrictions may cause the set-user-ID and set-group-ID bits of MODE or RFILE to be ignored. This behavior depends on the policy and functionality of the underlying chmod system call. When in doubt, check the underlying system behavior. For directories chmod preserves set-user-ID and set-group-ID bits unless you explicitly specify otherwise. You can set or clear the bits with symbolic modes like u+s and g-s. To clear these bits for directories with a numeric mode requires an additional leading zero like 00755, leading minus like -6000, or leading equals like =755. RESTRICTED DELETION FLAG OR STICKY BIT top The restricted deletion flag or sticky bit is a single bit, whose interpretation depends on the file type. For directories, it prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp. For regular files on some older systems, the bit saves the program's text image on the swap device so it will load more quickly when run; this is called the sticky bit. OPTIONS top Change the mode of each FILE to MODE. With --reference, change the mode of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's mode instead of specifying MODE values. RFILE is always dereferenced if a symbolic link. -R, --recursive change files and directories recursively --help display this help and exit --version output version information and exit Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(2) Full documentation <https://www.gnu.org/software/coreutils/chmod> or available locally via: info '(coreutils) chmod invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHMOD(1) Pages that refer to this page: bash(1), chacl(1), find(1), nfs4_setfacl(1), rsync(1), setfacl(1), chmod(2), fcntl(2), lp(4), rsyncd.conf(5), path_resolution(7), symlink(7), xattr(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the permissions of the current directory and all its subdirectories to 755. Bash Command:<START>find . -type d -exec chmod 755 {} \;<END>

Change the timestamp of symbolic link "somesymlink" to current date/time

touch -h somesymlink

['touch']

Output a Bash command to accomplish the following task. Task: Change the timestamp of symbolic link "somesymlink" to current date/time Bash Command:<START>touch -h somesymlink<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # touch\n\n> Create files and set access/modification times.\n> More information: <https://manned.org/man/freebsd-13.1/touch>.\n\n- Create specific files:\n\n`touch {{path/to/file1 path/to/file2 ...}}`\n\n- Set the file [a]ccess or [m]odification times to the current one and don't [c]reate file if it doesn't exist:\n\n`touch -c -{{a|m}} {{path/to/file1 path/to/file2 ...}}`\n\n- Set the file [t]ime to a specific value and don't [c]reate file if it doesn't exist:\n\n`touch -c -t {{YYYYMMDDHHMM.SS}} {{path/to/file1 path/to/file2 ...}}`\n\n- Set the file time of a specific file to the time of anothe[r] file and don't [c]reate file if it doesn't exist:\n\n`touch -c -r {{~/.emacs}} {{path/to/file1 path/to/file2 ...}}`\n Task: Change the timestamp of symbolic link "somesymlink" to current date/time Bash Command:<START>touch -h somesymlink<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: touch(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training touch(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | DATE STRING | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON TOUCH(1) User Commands TOUCH(1) NAME top touch - change file timestamps SYNOPSIS top touch [OPTION]... FILE... DESCRIPTION top Update the access and modification times of each FILE to the current time. A FILE argument that does not exist is created empty, unless -c or -h is supplied. A FILE argument string of - is handled specially and causes touch to change the times of the file associated with standard output. Mandatory arguments to long options are mandatory for short options too. -a change only the access time -c, --no-create do not create any files -d, --date=STRING parse STRING and use it instead of current time -f (ignored) -h, --no-dereference affect each symbolic link instead of any referenced file (useful only on systems that can change the timestamps of a symlink) -m change only the modification time -r, --reference=FILE use this file's times instead of current time -t STAMP use [[CC]YY]MMDDhhmm[.ss] instead of current time --time=WORD change the specified time: WORD is access, atime, or use: equivalent to -a WORD is modify or mtime: equivalent to -m --help display this help and exit --version output version information and exit Note that the -d and -t options accept different time-date formats. DATE STRING top The --date=STRING is a mostly free format human readable date string such as "Sun, 29 Feb 2004 16:21:42 -0800" or "2004-02-29 16:21:42" or even "next Thursday". A date string may contain items indicating calendar date, time of day, time zone, day of week, relative time, relative date, and numbers. An empty string indicates the beginning of the day. The date string format is more complex than is easily documented here but is fully described in the info documentation. AUTHOR top Written by Paul Rubin, Arnold Robbins, Jim Kingdon, David MacKenzie, and Randy Smith. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top Full documentation <https://www.gnu.org/software/coreutils/touch> or available locally via: info '(coreutils) touch invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 TOUCH(1) Pages that refer to this page: last(1@@util-linux), utime(2), utimensat(2), systemd-update-done.service(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the timestamp of symbolic link "somesymlink" to current date/time Bash Command:<START>touch -h somesymlink<END>

Change the user and group of all files and directories under /var/www to www-data:www-data

find /var/www -print0 | xargs -0 chown www-data:www-data

['find', 'xargs', 'chown']

Output a Bash command to accomplish the following task. Task: Change the user and group of all files and directories under /var/www to www-data:www-data Bash Command:<START>find /var/www -print0 | xargs -0 chown www-data:www-data<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the user and group of all files and directories under /var/www to www-data:www-data Bash Command:<START>find /var/www -print0 | xargs -0 chown www-data:www-data<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the user and group of all files and directories under /var/www to www-data:www-data Bash Command:<START>find /var/www -print0 | xargs -0 chown www-data:www-data<END>

Change the user to daisy for directories and subdirectories owned by harry

find . -type d -user harry -exec chown daisy {} \;

['find', 'chown']

Output a Bash command to accomplish the following task. Task: Change the user to daisy for directories and subdirectories owned by harry Bash Command:<START>find . -type d -user harry -exec chown daisy {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change the user to daisy for directories and subdirectories owned by harry Bash Command:<START>find . -type d -user harry -exec chown daisy {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change the user to daisy for directories and subdirectories owned by harry Bash Command:<START>find . -type d -user harry -exec chown daisy {} \;<END>

Change to directory 'foo' and print to terminal all received on standard input

cd foo | cat

['cat', 'cd']

Output a Bash command to accomplish the following task. Task: Change to directory 'foo' and print to terminal all received on standard input Bash Command:<START>cd foo | cat<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # cat\n\n> Print and concatenate files.\n> More information: <https://www.gnu.org/software/coreutils/cat>.\n\n- Print the contents of a file to `stdout`:\n\n`cat {{path/to/file}}`\n\n- Concatenate several files into an output file:\n\n`cat {{path/to/file1 path/to/file2 ...}} > {{path/to/output_file}}`\n\n- Append several files to an output file:\n\n`cat {{path/to/file1 path/to/file2 ...}} >> {{path/to/output_file}}`\n\n- Write `stdin` to a file:\n\n`cat - > {{path/to/file}}`\n\n- [n]umber all output lines:\n\n`cat -n {{path/to/file}}`\n\n- Display non-printable and whitespace characters (with `M-` prefix if non-ASCII):\n\n`cat -v -t -e {{path/to/file}}`\n # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to directory 'foo' and print to terminal all received on standard input Bash Command:<START>cd foo | cat<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: cat(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cat(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CAT(1) User Commands CAT(1) NAME top cat - concatenate files and print on the standard output SYNOPSIS top cat [OPTION]... [FILE]... DESCRIPTION top Concatenate FILE(s) to standard output. With no FILE, or when FILE is -, read standard input. -A, --show-all equivalent to -vET -b, --number-nonblank number nonempty output lines, overrides -n -e equivalent to -vE -E, --show-ends display $ at end of each line -n, --number number all output lines -s, --squeeze-blank suppress repeated empty output lines -t equivalent to -vT -T, --show-tabs display TAB characters as ^I -u (ignored) -v, --show-nonprinting use ^ and M- notation, except for LFD and TAB --help display this help and exit --version output version information and exit EXAMPLES top cat f - g Output f's contents, then standard input, then g's contents. cat Copy standard input to standard output. AUTHOR top Written by Torbjorn Granlund and Richard M. Stallman. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top tac(1) Full documentation <https://www.gnu.org/software/coreutils/cat> or available locally via: info '(coreutils) cat invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CAT(1) Pages that refer to this page: pmlogrewrite(1), pv(1), systemd-socket-activate(1), tac(1), ul(1), proc(5), cpuset(7), time_namespaces(7), readprofile(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to directory 'foo' and print to terminal all received on standard input Bash Command:<START>cd foo | cat<END>

Change to directory 'xyz' and resolve any symlinks in the resulting path, making the physical path the current one.

cd -P xyz

['cd']

Output a Bash command to accomplish the following task. Task: Change to directory 'xyz' and resolve any symlinks in the resulting path, making the physical path the current one. Bash Command:<START>cd -P xyz<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to directory 'xyz' and resolve any symlinks in the resulting path, making the physical path the current one. Bash Command:<START>cd -P xyz<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to directory 'xyz' and resolve any symlinks in the resulting path, making the physical path the current one. Bash Command:<START>cd -P xyz<END>

Change to directory listed in file '$HOME/.lastdir'

cd `cat $HOME/.lastdir`

['cat', 'cd']

Output a Bash command to accomplish the following task. Task: Change to directory listed in file '$HOME/.lastdir' Bash Command:<START>cd `cat $HOME/.lastdir`<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # cat\n\n> Print and concatenate files.\n> More information: <https://www.gnu.org/software/coreutils/cat>.\n\n- Print the contents of a file to `stdout`:\n\n`cat {{path/to/file}}`\n\n- Concatenate several files into an output file:\n\n`cat {{path/to/file1 path/to/file2 ...}} > {{path/to/output_file}}`\n\n- Append several files to an output file:\n\n`cat {{path/to/file1 path/to/file2 ...}} >> {{path/to/output_file}}`\n\n- Write `stdin` to a file:\n\n`cat - > {{path/to/file}}`\n\n- [n]umber all output lines:\n\n`cat -n {{path/to/file}}`\n\n- Display non-printable and whitespace characters (with `M-` prefix if non-ASCII):\n\n`cat -v -t -e {{path/to/file}}`\n # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to directory listed in file '$HOME/.lastdir' Bash Command:<START>cd `cat $HOME/.lastdir`<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: cat(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cat(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CAT(1) User Commands CAT(1) NAME top cat - concatenate files and print on the standard output SYNOPSIS top cat [OPTION]... [FILE]... DESCRIPTION top Concatenate FILE(s) to standard output. With no FILE, or when FILE is -, read standard input. -A, --show-all equivalent to -vET -b, --number-nonblank number nonempty output lines, overrides -n -e equivalent to -vE -E, --show-ends display $ at end of each line -n, --number number all output lines -s, --squeeze-blank suppress repeated empty output lines -t equivalent to -vT -T, --show-tabs display TAB characters as ^I -u (ignored) -v, --show-nonprinting use ^ and M- notation, except for LFD and TAB --help display this help and exit --version output version information and exit EXAMPLES top cat f - g Output f's contents, then standard input, then g's contents. cat Copy standard input to standard output. AUTHOR top Written by Torbjorn Granlund and Richard M. Stallman. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top tac(1) Full documentation <https://www.gnu.org/software/coreutils/cat> or available locally via: info '(coreutils) cat invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CAT(1) Pages that refer to this page: pmlogrewrite(1), pv(1), systemd-socket-activate(1), tac(1), ul(1), proc(5), cpuset(7), time_namespaces(7), readprofile(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to directory listed in file '$HOME/.lastdir' Bash Command:<START>cd `cat $HOME/.lastdir`<END>

Change to folder where the oracle binary is.

cd "$(dirname "$(which oracle)")"

['dirname', 'cd']

Output a Bash command to accomplish the following task. Task: Change to folder where the oracle binary is. Bash Command:<START>cd "$(dirname "$(which oracle)")"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # dirname\n\n> Calculates the parent directory of a file or directory path.\n> More information: <https://www.gnu.org/software/coreutils/dirname>.\n\n- Calculate the parent directory of a given path:\n\n`dirname {{path/to/file_or_directory}}`\n\n- Calculate the parent directory of multiple paths:\n\n`dirname {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n\n- Delimit output with a NUL character instead of a newline (useful when combining with `xargs`):\n\n`dirname --zero {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to folder where the oracle binary is. Bash Command:<START>cd "$(dirname "$(which oracle)")"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: dirname(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training dirname(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIRNAME(1) User Commands DIRNAME(1) NAME top dirname - strip last component from file name SYNOPSIS top dirname [OPTION] NAME... DESCRIPTION top Output each NAME with its last non-slash component and trailing slashes removed; if NAME contains no /'s, output '.' (meaning the current directory). -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit EXAMPLES top dirname /usr/bin/ -> "/usr" dirname dir1/str dir2/str -> "dir1" followed by "dir2" dirname stdio.h -> "." AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top basename(1), readlink(1) Full documentation <https://www.gnu.org/software/coreutils/dirname> or available locally via: info '(coreutils) dirname invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DIRNAME(1) Pages that refer to this page: basename(1), basename(3) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to folder where the oracle binary is. Bash Command:<START>cd "$(dirname "$(which oracle)")"<END>

Change to folder where the oracle binary is.

cd "$(dirname $(which oracle))"

['dirname', 'cd']

Output a Bash command to accomplish the following task. Task: Change to folder where the oracle binary is. Bash Command:<START>cd "$(dirname $(which oracle))"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # dirname\n\n> Calculates the parent directory of a file or directory path.\n> More information: <https://www.gnu.org/software/coreutils/dirname>.\n\n- Calculate the parent directory of a given path:\n\n`dirname {{path/to/file_or_directory}}`\n\n- Calculate the parent directory of multiple paths:\n\n`dirname {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n\n- Delimit output with a NUL character instead of a newline (useful when combining with `xargs`):\n\n`dirname --zero {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to folder where the oracle binary is. Bash Command:<START>cd "$(dirname $(which oracle))"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: dirname(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training dirname(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIRNAME(1) User Commands DIRNAME(1) NAME top dirname - strip last component from file name SYNOPSIS top dirname [OPTION] NAME... DESCRIPTION top Output each NAME with its last non-slash component and trailing slashes removed; if NAME contains no /'s, output '.' (meaning the current directory). -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit EXAMPLES top dirname /usr/bin/ -> "/usr" dirname dir1/str dir2/str -> "dir1" followed by "dir2" dirname stdio.h -> "." AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top basename(1), readlink(1) Full documentation <https://www.gnu.org/software/coreutils/dirname> or available locally via: info '(coreutils) dirname invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DIRNAME(1) Pages that refer to this page: basename(1), basename(3) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to folder where the oracle binary is. Bash Command:<START>cd "$(dirname $(which oracle))"<END>

Change to folder where the oracle binary is.

cd $(dirname $(which oracle))

['dirname', 'cd']

Output a Bash command to accomplish the following task. Task: Change to folder where the oracle binary is. Bash Command:<START>cd $(dirname $(which oracle))<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # dirname\n\n> Calculates the parent directory of a file or directory path.\n> More information: <https://www.gnu.org/software/coreutils/dirname>.\n\n- Calculate the parent directory of a given path:\n\n`dirname {{path/to/file_or_directory}}`\n\n- Calculate the parent directory of multiple paths:\n\n`dirname {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n\n- Delimit output with a NUL character instead of a newline (useful when combining with `xargs`):\n\n`dirname --zero {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to folder where the oracle binary is. Bash Command:<START>cd $(dirname $(which oracle))<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: dirname(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training dirname(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIRNAME(1) User Commands DIRNAME(1) NAME top dirname - strip last component from file name SYNOPSIS top dirname [OPTION] NAME... DESCRIPTION top Output each NAME with its last non-slash component and trailing slashes removed; if NAME contains no /'s, output '.' (meaning the current directory). -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit EXAMPLES top dirname /usr/bin/ -> "/usr" dirname dir1/str dir2/str -> "dir1" followed by "dir2" dirname stdio.h -> "." AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top basename(1), readlink(1) Full documentation <https://www.gnu.org/software/coreutils/dirname> or available locally via: info '(coreutils) dirname invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DIRNAME(1) Pages that refer to this page: basename(1), basename(3) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to folder where the oracle binary is. Bash Command:<START>cd $(dirname $(which oracle))<END>

Change to folder where the oracle binary is.

cd $(dirname `which oracle`)

['dirname', 'cd']

Output a Bash command to accomplish the following task. Task: Change to folder where the oracle binary is. Bash Command:<START>cd $(dirname `which oracle`)<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # dirname\n\n> Calculates the parent directory of a file or directory path.\n> More information: <https://www.gnu.org/software/coreutils/dirname>.\n\n- Calculate the parent directory of a given path:\n\n`dirname {{path/to/file_or_directory}}`\n\n- Calculate the parent directory of multiple paths:\n\n`dirname {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n\n- Delimit output with a NUL character instead of a newline (useful when combining with `xargs`):\n\n`dirname --zero {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to folder where the oracle binary is. Bash Command:<START>cd $(dirname `which oracle`)<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: dirname(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training dirname(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIRNAME(1) User Commands DIRNAME(1) NAME top dirname - strip last component from file name SYNOPSIS top dirname [OPTION] NAME... DESCRIPTION top Output each NAME with its last non-slash component and trailing slashes removed; if NAME contains no /'s, output '.' (meaning the current directory). -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit EXAMPLES top dirname /usr/bin/ -> "/usr" dirname dir1/str dir2/str -> "dir1" followed by "dir2" dirname stdio.h -> "." AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top basename(1), readlink(1) Full documentation <https://www.gnu.org/software/coreutils/dirname> or available locally via: info '(coreutils) dirname invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DIRNAME(1) Pages that refer to this page: basename(1), basename(3) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to folder where the oracle binary is. Bash Command:<START>cd $(dirname `which oracle`)<END>

Change to location of '$TARGET_FILE' file.

cd `dirname $TARGET_FILE`

['cd', 'dirname']

Output a Bash command to accomplish the following task. Task: Change to location of '$TARGET_FILE' file. Bash Command:<START>cd `dirname $TARGET_FILE`<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n # dirname\n\n> Calculates the parent directory of a file or directory path.\n> More information: <https://www.gnu.org/software/coreutils/dirname>.\n\n- Calculate the parent directory of a given path:\n\n`dirname {{path/to/file_or_directory}}`\n\n- Calculate the parent directory of multiple paths:\n\n`dirname {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n\n- Delimit output with a NUL character instead of a newline (useful when combining with `xargs`):\n\n`dirname --zero {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n Task: Change to location of '$TARGET_FILE' file. Bash Command:<START>cd `dirname $TARGET_FILE`<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. dirname(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training dirname(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIRNAME(1) User Commands DIRNAME(1) NAME top dirname - strip last component from file name SYNOPSIS top dirname [OPTION] NAME... DESCRIPTION top Output each NAME with its last non-slash component and trailing slashes removed; if NAME contains no /'s, output '.' (meaning the current directory). -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit EXAMPLES top dirname /usr/bin/ -> "/usr" dirname dir1/str dir2/str -> "dir1" followed by "dir2" dirname stdio.h -> "." AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top basename(1), readlink(1) Full documentation <https://www.gnu.org/software/coreutils/dirname> or available locally via: info '(coreutils) dirname invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DIRNAME(1) Pages that refer to this page: basename(1), basename(3) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to location of '$TARGET_FILE' file. Bash Command:<START>cd `dirname $TARGET_FILE`<END>

Change to parent directory and resolve any symlinks in the resulting path, making the physical path the current one.

cd -P ..

['cd']

Output a Bash command to accomplish the following task. Task: Change to parent directory and resolve any symlinks in the resulting path, making the physical path the current one. Bash Command:<START>cd -P ..<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to parent directory and resolve any symlinks in the resulting path, making the physical path the current one. Bash Command:<START>cd -P ..<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to parent directory and resolve any symlinks in the resulting path, making the physical path the current one. Bash Command:<START>cd -P ..<END>

Change to the directory containing the "oracle" executable

cd "$(dirname "$(which oracle)")"

['dirname', 'cd']

Output a Bash command to accomplish the following task. Task: Change to the directory containing the "oracle" executable Bash Command:<START>cd "$(dirname "$(which oracle)")"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # dirname\n\n> Calculates the parent directory of a file or directory path.\n> More information: <https://www.gnu.org/software/coreutils/dirname>.\n\n- Calculate the parent directory of a given path:\n\n`dirname {{path/to/file_or_directory}}`\n\n- Calculate the parent directory of multiple paths:\n\n`dirname {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n\n- Delimit output with a NUL character instead of a newline (useful when combining with `xargs`):\n\n`dirname --zero {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to the directory containing the "oracle" executable Bash Command:<START>cd "$(dirname "$(which oracle)")"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: dirname(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training dirname(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIRNAME(1) User Commands DIRNAME(1) NAME top dirname - strip last component from file name SYNOPSIS top dirname [OPTION] NAME... DESCRIPTION top Output each NAME with its last non-slash component and trailing slashes removed; if NAME contains no /'s, output '.' (meaning the current directory). -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit EXAMPLES top dirname /usr/bin/ -> "/usr" dirname dir1/str dir2/str -> "dir1" followed by "dir2" dirname stdio.h -> "." AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top basename(1), readlink(1) Full documentation <https://www.gnu.org/software/coreutils/dirname> or available locally via: info '(coreutils) dirname invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DIRNAME(1) Pages that refer to this page: basename(1), basename(3) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to the directory containing the "oracle" executable Bash Command:<START>cd "$(dirname "$(which oracle)")"<END>

Change to the directory pointed by variable TAG

cd "$TAG"

['cd']

Output a Bash command to accomplish the following task. Task: Change to the directory pointed by variable TAG Bash Command:<START>cd "$TAG"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n Task: Change to the directory pointed by variable TAG Bash Command:<START>cd "$TAG"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change to the directory pointed by variable TAG Bash Command:<START>cd "$TAG"<END>

Change user ownership to `foo' for files with UID=1005

find / -user 1005 -exec chown -h foo {} \;

['find', 'chown']

Output a Bash command to accomplish the following task. Task: Change user ownership to `foo' for files with UID=1005 Bash Command:<START>find / -user 1005 -exec chown -h foo {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change user ownership to `foo' for files with UID=1005 Bash Command:<START>find / -user 1005 -exec chown -h foo {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change user ownership to `foo' for files with UID=1005 Bash Command:<START>find / -user 1005 -exec chown -h foo {} \;<END>

Change user to "amzadm" and group to "root" of "/usr/bin/aws"

chown amzadm.root /usr/bin/aws

['chown']

Output a Bash command to accomplish the following task. Task: Change user to "amzadm" and group to "root" of "/usr/bin/aws" Bash Command:<START>chown amzadm.root /usr/bin/aws<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chown\n\n> Change user and group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chown>.\n\n- Change the owner user of a file/directory:\n\n`chown {{user}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group of a file/directory:\n\n`chown {{user}}:{{group}} {{path/to/file_or_directory}}`\n\n- Change the owner user and group to both have the name `user`:\n\n`chown {{user}}: {{path/to/file_or_directory}}`\n\n- Recursively change the owner of a directory and its contents:\n\n`chown -R {{user}} {{path/to/directory}}`\n\n- Change the owner of a symbolic link:\n\n`chown -h {{user}} {{path/to/symlink}}`\n\n- Change the owner of a file/directory to match a reference file:\n\n`chown --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Change user to "amzadm" and group to "root" of "/usr/bin/aws" Bash Command:<START>chown amzadm.root /usr/bin/aws<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chown(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chown(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHOWN(1) User Commands CHOWN(1) NAME top chown - change file owner and group SYNOPSIS top chown [OPTION]... [OWNER][:[GROUP]] FILE... chown [OPTION]... --reference=RFILE FILE... DESCRIPTION top This manual page documents the GNU version of chown. chown changes the user and/or group ownership of each given file. If only an owner (a user name or numeric user ID) is given, that user is made the owner of each given file, and the files' group is not changed. If the owner is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well. If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user's login group. If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp. If only a colon is given, or if the entire operand is empty, neither the owner nor the group is changed. OPTIONS top Change the owner and/or group of each FILE to OWNER and/or GROUP. With --reference, change the owner and group of each FILE to those of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --from=CURRENT_OWNER:CURRENT_GROUP change the owner and/or group of each file only if its current owner and/or group match those specified here. Either may be omitted, in which case a match is not required for the omitted attribute --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values. RFILE is always dereferenced. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit Owner is unchanged if missing. Group is unchanged if missing, but changed to login group if implied by a ':' following a symbolic OWNER. OWNER and GROUP may be numeric as well as symbolic. EXAMPLES top chown root /u Change the owner of /u to "root". chown root:staff /u Likewise, but also change its group to "staff". chown -hR root /u Change the owner of /u and subfiles to "root". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(2) Full documentation <https://www.gnu.org/software/coreutils/chown> or available locally via: info '(coreutils) chown invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHOWN(1) Pages that refer to this page: chgrp(1), chown(2), fd(4), hd(4), initrd(4), lp(4), mem(4), null(4), ram(4), tty(4), ttyS(4), symlink(7), sm-notify(8), start-stop-daemon(8), statd(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Change user to "amzadm" and group to "root" of "/usr/bin/aws" Bash Command:<START>chown amzadm.root /usr/bin/aws<END>

Changes group ownership of '/etc/btsync/[prefered conf name].conf' to 'btsync'.

chgrp btsync /etc/btsync/[prefered conf name].conf

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of '/etc/btsync/[prefered conf name].conf' to 'btsync'. Bash Command:<START>chgrp btsync /etc/btsync/[prefered conf name].conf<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of '/etc/btsync/[prefered conf name].conf' to 'btsync'. Bash Command:<START>chgrp btsync /etc/btsync/[prefered conf name].conf<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of '/etc/btsync/[prefered conf name].conf' to 'btsync'. Bash Command:<START>chgrp btsync /etc/btsync/[prefered conf name].conf<END>

Changes group ownership of '/home/www-user/php_user.sh' to 'www-data'.

chgrp www-data /home/www-user/php_user.sh

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of '/home/www-user/php_user.sh' to 'www-data'. Bash Command:<START>chgrp www-data /home/www-user/php_user.sh<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of '/home/www-user/php_user.sh' to 'www-data'. Bash Command:<START>chgrp www-data /home/www-user/php_user.sh<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of '/home/www-user/php_user.sh' to 'www-data'. Bash Command:<START>chgrp www-data /home/www-user/php_user.sh<END>

Changes group ownership of '/var/run/fcgiwrap.socket' to 'forge'.

chgrp forge /var/run/fcgiwrap.socket

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of '/var/run/fcgiwrap.socket' to 'forge'. Bash Command:<START>chgrp forge /var/run/fcgiwrap.socket<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of '/var/run/fcgiwrap.socket' to 'forge'. Bash Command:<START>chgrp forge /var/run/fcgiwrap.socket<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of '/var/run/fcgiwrap.socket' to 'forge'. Bash Command:<START>chgrp forge /var/run/fcgiwrap.socket<END>

Changes group ownership of 'logdir' to 'loggroup'.

chgrp loggroup logdir

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of 'logdir' to 'loggroup'. Bash Command:<START>chgrp loggroup logdir<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of 'logdir' to 'loggroup'. Bash Command:<START>chgrp loggroup logdir<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of 'logdir' to 'loggroup'. Bash Command:<START>chgrp loggroup logdir<END>

Changes group ownership of 'myprog' to 'groupb'.

chgrp groupb myprog

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of 'myprog' to 'groupb'. Bash Command:<START>chgrp groupb myprog<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of 'myprog' to 'groupb'. Bash Command:<START>chgrp groupb myprog<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of 'myprog' to 'groupb'. Bash Command:<START>chgrp groupb myprog<END>

Changes group ownership of 'myprogram' to ${USER} (the current user)

chgrp "${USER}" myprogram

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of 'myprogram' to ${USER} (the current user) Bash Command:<START>chgrp "${USER}" myprogram<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of 'myprogram' to ${USER} (the current user) Bash Command:<START>chgrp "${USER}" myprogram<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of 'myprogram' to ${USER} (the current user) Bash Command:<START>chgrp "${USER}" myprogram<END>

Changes group ownership of 'public' and 'private' to 'god'.

chgrp god public private

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of 'public' and 'private' to 'god'. Bash Command:<START>chgrp god public private<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of 'public' and 'private' to 'god'. Bash Command:<START>chgrp god public private<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of 'public' and 'private' to 'god'. Bash Command:<START>chgrp god public private<END>

Changes group ownership of 'public' to 'pub'.

chgrp pub public

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of 'public' to 'pub'. Bash Command:<START>chgrp pub public<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of 'public' to 'pub'. Bash Command:<START>chgrp pub public<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of 'public' to 'pub'. Bash Command:<START>chgrp pub public<END>

Changes group ownership of 'shared' to 'Workers'.

chgrp Workers shared

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of 'shared' to 'Workers'. Bash Command:<START>chgrp Workers shared<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of 'shared' to 'Workers'. Bash Command:<START>chgrp Workers shared<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of 'shared' to 'Workers'. Bash Command:<START>chgrp Workers shared<END>

Changes group ownership of 'target_directory' to 'target_group'.

chgrp target_group target_directory

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes group ownership of 'target_directory' to 'target_group'. Bash Command:<START>chgrp target_group target_directory<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes group ownership of 'target_directory' to 'target_group'. Bash Command:<START>chgrp target_group target_directory<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of 'target_directory' to 'target_group'. Bash Command:<START>chgrp target_group target_directory<END>

Changes group ownership of /sys/class/gpio/export and /sys/class/gpio/unexport to 'gpio'.

sudo chgrp gpio /sys/class/gpio/export /sys/class/gpio/unexport

['chgrp', 'sudo']

Output a Bash command to accomplish the following task. Task: Changes group ownership of /sys/class/gpio/export and /sys/class/gpio/unexport to 'gpio'. Bash Command:<START>sudo chgrp gpio /sys/class/gpio/export /sys/class/gpio/unexport<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n # sudo\n\n> Executes a single command as the superuser or another user.\n> More information: <https://www.sudo.ws/sudo.html>.\n\n- Run a command as the superuser:\n\n`sudo {{less /var/log/syslog}}`\n\n- Edit a file as the superuser with your default editor:\n\n`sudo --edit {{/etc/fstab}}`\n\n- Run a command as another user and/or group:\n\n`sudo --user={{user}} --group={{group}} {{id -a}}`\n\n- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):\n\n`sudo !!`\n\n- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login`\n\n- Launch the default shell with superuser privileges without changing the environment:\n\n`sudo --shell`\n\n- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login --user={{user}}`\n\n- List the allowed (and forbidden) commands for the invoking user:\n\n`sudo --list`\n Task: Changes group ownership of /sys/class/gpio/export and /sys/class/gpio/unexport to 'gpio'. Bash Command:<START>sudo chgrp gpio /sys/class/gpio/export /sys/class/gpio/unexport<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sudo(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sudo(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON SUDO(8) System Manager's Manual SUDO(8) NAME top sudo, sudoedit execute a command as another user SYNOPSIS top sudo -h | -K | -k | -V sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command [arg ...]] sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] [VAR=value] [-i | -s] [command [arg ...]] sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] file ... DESCRIPTION top allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy. supports a plugin architecture for security policies, auditing, and input/output logging. Third parties can develop and distribute their own plugins to work seamlessly with the front- end. The default security policy is sudoers, which is configured via the file /etc/sudoers, or via LDAP. See the Plugins section for more information. The security policy determines what privileges, if any, a user has to run . The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific; the default password prompt timeout for the sudoers security policy is 5 minutes. Security policies may support credential caching to allow the user to run again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running with the -v option, a user can update the cached credentials without running a command. On systems where is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced. When invoked as sudoedit, the -e option (described below), is implied. Security policies and audit plugins may log successful and failed attempts to run . If an I/O plugin is configured, the running command's input and output may be logged as well. The options are as follows: -A, --askpass Normally, if requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example: # Path to askpass helper program Path askpass /usr/X11R6/bin/ssh-askpass If no askpass program is available, will exit with an error. -B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used. -b, --background Run the given command in the background. It is not possible to use shell job control to manipulate background processes started by . Most interactive commands will fail to work properly in background mode. -C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, will close all open file descriptors other than standard input, standard output, and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option. -D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory. -E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment. --preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times. -e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken: 1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used. 3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy: Symbolic links may not be edited (version 1.8.15 and higher). Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher). Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher). Users are never allowed to edit device special files. If the specified file does not exist, it will be created. Unlike most commands run by sudo, the editor is run with the invoking user's environment unmodified. If the temporary file becomes empty after editing, the user will be prompted before it is installed. If, for some reason, is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file. -g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the # character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the # be escaped with a backslash (\). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use. -H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior. -h, --help Display a short help message to the standard output and exit. -h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. The sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host. -i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login- specific resource files such as .profile, .bash_profile, or .login will be read by the shell. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use. -K, --remove-timestamp Similar to the -k option, except that it removes every cached credential for the user, regardless of the terminal or parent process ID. The next time is run, a password must be entered if the security policy requires authentication. It is not possible to use the -K option in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching. -k, --reset-timestamp When used without a command, invalidates the user's cached credentials for the current session. The next time is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with commands run in a different terminal session. See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke permissions from a .logout file. When used in conjunction with a command or an option that may require a password, this option will cause to ignore the user's cached credentials. As a result, will prompt for a password (if one is required by the security policy) and will not update the user's cached credentials. Not all security policies support credential caching. -l, --list If no command is specified, list the privileges for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format. If a command is specified and is permitted by the security policy for the invoking user (or the, user specified by the -U option) on the current host, the fully-qualified path to the command is displayed along with any args. If -l is specified more than once (and the security policy supports it), the matching rule is displayed in a verbose format along with the command. If a command is specified but not allowed by the policy, will exit with a status value of 1. -N, --no-update Do not update the user's cached credentials, even if the user successfully authenticates. Unlike the -k flag, existing cached credentials are used if they are valid. To detect when the user's cached credentials are valid (or when no authentication is required), the following can be used: sudo -Nnv Not all security policies support credential caching. -n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, will display an error message and exit. -P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user. -p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent (%) escape sequences are supported by the sudoers policy: %H expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in sudoers(5)) %h expanded to the local host name without the domain name %p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5)) %U expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified) %u expanded to the invoking user's login name %% two consecutive % characters are collapsed into a single % character The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers. -R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory. -S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device. -s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. -U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. When using the sudoers policy, the -U option is restricted to the root user and users with either the list priviege for the specified user or the ability to run any command as root or user on the current host. -T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the user's ability to set timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled. -u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the # character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the # be escaped with a backslash (\). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this. -V, --version Print the version string as well as the version string of any configured plugins. If the invoking user is already root, the -V option will display the options passed to configure when was built; plugins may display additional information such as default options. -v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials. -- The -- is used to delimit the end of the options. Subsequent options are passed to the command. Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input. Environment variables to be set for the command may also be passed as options to in the form VAR=value, for example LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be subject to restrictions imposed by the security policy plugin. The sudoers policy subjects environment variables passed as options to the same restrictions as existing environment variables with one important difference. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information. COMMAND EXECUTION top When executes a command, the security policy specifies the execution environment for the command. Typically, the real and effective user and group and IDs are set to match those of the target user, as specified in the password database, and the group vector is initialized based on the group database (unless the -P option was specified). The following parameters may be specified by security policy: real and effective user-ID real and effective group-ID supplementary group-IDs the environment list current working directory file creation mode mask (umask) scheduling priority (aka nice value) Process model There are two distinct ways can run a command. If an I/O logging plugin is configured to log terminal I/O, or if the security policy explicitly requests it, a new pseudo-terminal (pty) is allocated and fork(2) is used to create a second process, referred to as the monitor. The monitor creates a new terminal session with itself as the leader and the pty as its controlling terminal, calls fork(2) again, sets up the execution environment as described above, and then uses the execve(2) system call to run the command in the child process. The monitor exists to relay job control signals between the user's terminal and the pty the command is being run in. This makes it possible to suspend and resume the command normally. Without the monitor, the command would be in what POSIX terms an orphaned process group and it would not receive any job control signals from the kernel. When the command exits or is terminated by a signal, the monitor passes the command's exit status to the main process and exits. After receiving the command's exit status, the main process passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugin, and exits. This mode is the default for sudo versions 1.9.14 and above when using the sudoers policy. If no pty is used, calls fork(2), sets up the execution environment as described above, and uses the execve(2) system call to run the command in the child process. The main process waits until the command has completed, then passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugins, and exits. As a special case, if the policy plugin does not define a close function, will execute the command directly instead of calling fork(2) first. The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled. Both pam_session and pam_setcred are enabled by default on systems using PAM. This mode is the default for sudo versions prior to 1.9.14 when using the sudoers policy. On systems that use PAM, the security policy's close function is responsible for closing the PAM session. It may also log the command's exit status. Signal handling When the command is run as a child of the process, will relay signals it receives to the command. The SIGINT and SIGQUIT signals are only relayed when the command is being run in a new pty or when the signal was sent by a user process, not the kernel. This prevents the command from receiving SIGINT twice each time the user enters control-C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by . As a special case, will not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) utility sends SIGTERM to all non-system processes other than itself before rebooting the system. This prevents from relaying the SIGTERM signal it received back to reboot(8), which might then exit before the system was actually rebooted, leaving it in a half-dead state similar to single user mode. Note, however, that this check only applies to the command run by and not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via may cause the system to end up in this undefined state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the command and the calling process). Plugins Plugins may be specified via Plugin directives in the sudo.conf(5) file. They may be loaded as dynamic shared objects (on systems that support them), or compiled directly into the binary. If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, will use sudoers(5) for the policy, auditing, and I/O logging plugins. See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for more information about the plugin architecture. EXIT VALUE top Upon successful execution of a command, the exit status from will be the exit status of the program that was executed. If the command terminated due to receipt of a signal, will send itself the same signal that terminated the command. If the -l option was specified without a command, will exit with a value of 0 if the user is allowed to run and they authenticated successfully (as required by the security policy). If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by the security policy, otherwise it will be 1. If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, exits with a value of 1. In the latter case, the error string is printed to the standard error. If cannot stat(2) one or more entries in the user's PATH, an error is printed to the standard error. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat(2) to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. SECURITY NOTES top tries to be safe when executing external commands. To prevent command spoofing, checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the program that executes. Users should never be granted privileges to execute files that are writable by the user or that reside in a directory that is writable by the user. If the user can modify or replace the command there is no way to limit what additional commands they can run. By default, will only log the command it explicitly runs. If a user runs a command such as sudo su or sudo sh, subsequent commands run from that shell are not subject to sudo's security policy. The same is true for commands that offer shell escapes (including most editors). If I/O logging is enabled, subsequent commands will have their input and/or output logged, but there will not be traditional logs for those commands. Because of this, care must be taken when giving users access to commands via to verify that the command does not inadvertently give the user an effective root shell. For information on ways to address this, see the Preventing shell escapes section in sudoers(5). To prevent the disclosure of potentially sensitive information, disables core dumps by default while it is executing (they are re-enabled for the command that is run). This historical practice dates from a time when most operating systems allowed set-user-ID processes to dump core by default. To aid in debugging crashes, you may wish to re-enable core dumps by setting disable_coredump to false in the sudo.conf(5) file as follows: Set disable_coredump false See the sudo.conf(5) manual for more information. ENVIRONMENT top utilizes the following environment variables. The security policy has control over the actual content of the command's environment. EDITOR Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set. MAIL Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is present in the env_keep list). HOME Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the env_keep list. LOGNAME Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list). PATH May be overridden by the security policy. SHELL Used to determine shell to run with -s option. SUDO_ASKPASS Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified. SUDO_COMMAND Set to the command run by sudo, including any args. The args are truncated at 4096 characters to prevent a potential execution error. SUDO_EDITOR Default editor to use in -e (sudoedit) mode. SUDO_GID Set to the group-ID of the user who invoked sudo. SUDO_PROMPT Used as the default password prompt unless the -p option was specified. SUDO_PS1 If set, PS1 will be set to its value for the program being run. SUDO_UID Set to the user-ID of the user who invoked sudo. SUDO_USER Set to the login name of the user who invoked sudo. USER Set to the same value as LOGNAME, described above. VISUAL Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set. FILES top /etc/sudo.conf front-end configuration EXAMPLES top The following examples assume a properly configured security policy. To get a file listing of an unreadable directory: $ sudo ls /usr/local/protected To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root: $ sudo -u yaz ls ~yaz To edit the index.html file as user www: $ sudoedit -u www ~www/htdocs/index.html To view system logs only accessible to root and users in the adm group: $ sudo -g adm more /var/log/syslog To run an editor as jim with a different primary group: $ sudoedit -u jim -g audio ~jim/sound.txt To shut down a machine: $ sudo shutdown -r +15 "quick reboot" To make a usage listing of the directories in the /home partition. The commands are run in a sub-shell to allow the cd command and file redirection to work. $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" DIAGNOSTICS top Error messages produced by include: editing files in a writable directory is not permitted By default, sudoedit does not permit editing a file when any of the parent directories are writable by the invoking user. This avoids a race condition that could allow the user to overwrite an arbitrary file. See the sudoedit_checkdir option in sudoers(5) for more information. editing symbolic links is not permitted By default, sudoedit does not follow symbolic links when opening files. See the sudoedit_follow option in sudoers(5) for more information. effective uid is not 0, is sudo installed setuid root? was not run with root privileges. The binary must be owned by the root user and have the set-user-ID bit set. Also, it must not be located on a file system mounted with the nosuid option or on an NFS file system that maps uid 0 to an unprivileged uid. effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges? was not run with root privileges. The binary has the proper owner and permissions but it still did not run with root privileges. The most common reason for this is that the file system the binary is located on is mounted with the nosuid option or it is an NFS file system that maps uid 0 to an unprivileged uid. fatal error, unable to load plugins An error occurred while loading or initializing the plugins specified in sudo.conf(5). invalid environment variable name One or more environment variable names specified via the -E option contained an equal sign (=). The arguments to the -E option should be environment variable names without an associated value. no password was provided When tried to read the password, it did not receive any characters. This may happen if no terminal is available (or the -S option is specified) and the standard input has been redirected from /dev/null. a terminal is required to read the password needs to read the password but there is no mechanism available for it to do so. A terminal is not present to read the password from, has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the sudo.conf(5) file or the SUDO_ASKPASS environment variable. no writable temporary directory found sudoedit was unable to find a usable temporary directory in which to store its intermediate files. The no new privileges flag is set, which prevents sudo from running as root. was run by a process that has the Linux no new privileges flag is set. This causes the set-user-ID bit to be ignored when running an executable, which will prevent from functioning. The most likely cause for this is running within a container that sets this flag. Check the documentation to see if it is possible to configure the container such that the flag is not set. sudo must be owned by uid 0 and have the setuid bit set was not run with root privileges. The binary does not have the correct owner or permissions. It must be owned by the root user and have the set-user-ID bit set. sudoedit is not supported on this platform It is only possible to run sudoedit on systems that support setting the effective user-ID. timed out reading password The user did not enter a password before the password timeout (5 minutes by default) expired. you do not exist in the passwd database Your user-ID does not appear in the system passwd database. you may not specify environment variables in edit mode It is only possible to specify environment variables when running a command. When editing a file, the editor is run with the user's environment unmodified. SEE ALSO top su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8) HISTORY top See the HISTORY.md file in the distribution (https://www.sudo.ws/about/history/) for a brief history of sudo. AUTHORS top Many people have worked on over the years; this version consists of code written primarily by: Todd C. Miller See the CONTRIBUTORS.md file in the distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed to . CAVEATS top There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via . Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with the sudoers(5) plugin's noexec functionality. It is not meaningful to run the cd command directly via sudo, e.g., $ sudo cd /usr/local/protected since when the command exits the parent process (your shell) will still be the same. The -D option can be used to run a command in a specific directory. Running shell scripts via can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, set-user-ID shell scripts are generally safe). BUGS top If you believe you have found a bug in , you can submit a bug report at https://bugzilla.sudo.ws/ SUPPORT top Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives. DISCLAIMER top is provided AS IS and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE.md file distributed with or https://www.sudo.ws/about/license/ for complete details. COLOPHON top This page is part of the sudo (execute a command as another user) project. Information about the project can be found at https://www.sudo.ws/. If you have a bug report for this manual page, see https://bugzilla.sudo.ws/. This page was obtained from the project's upstream Git repository https://github.com/sudo-project/sudo on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Sudo 1.9.15p4 August 9, 2023 SUDO(8) Pages that refer to this page: homectl(1), journalctl(1), localectl(1), loginctl(1), machinectl(1), portablectl(1), setpriv(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), uid0(1), userdbctl(1), nsswitch.conf(5), credentials(7), systemd-tmpfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes group ownership of /sys/class/gpio/export and /sys/class/gpio/unexport to 'gpio'. Bash Command:<START>sudo chgrp gpio /sys/class/gpio/export /sys/class/gpio/unexport<END>

Changes the group of defined file.

chgrp

['chgrp']

Output a Bash command to accomplish the following task. Task: Changes the group of defined file. Bash Command:<START>chgrp<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # chgrp\n\n> Change group ownership of files and directories.\n> More information: <https://www.gnu.org/software/coreutils/chgrp>.\n\n- Change the owner group of a file/directory:\n\n`chgrp {{group}} {{path/to/file_or_directory}}`\n\n- Recursively change the owner group of a directory and its contents:\n\n`chgrp -R {{group}} {{path/to/directory}}`\n\n- Change the owner group of a symbolic link:\n\n`chgrp -h {{group}} {{path/to/symlink}}`\n\n- Change the owner group of a file/directory to match a reference file:\n\n`chgrp --reference={{path/to/reference_file}} {{path/to/file_or_directory}}`\n Task: Changes the group of defined file. Bash Command:<START>chgrp<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: chgrp(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training chgrp(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CHGRP(1) User Commands CHGRP(1) NAME top chgrp - change group ownership SYNOPSIS top chgrp [OPTION]... GROUP FILE... chgrp [OPTION]... --reference=RFILE FILE... DESCRIPTION top Change the group of each FILE to GROUP. With --reference, change the group of each FILE to that of RFILE. -c, --changes like verbose but report only when a change is made -f, --silent, --quiet suppress most error messages -v, --verbose output a diagnostic for every file processed --dereference affect the referent of each symbolic link (this is the default), rather than the symbolic link itself -h, --no-dereference affect symbolic links instead of any referenced file (useful only on systems that can change the ownership of a symlink) --no-preserve-root do not treat '/' specially (the default) --preserve-root fail to operate recursively on '/' --reference=RFILE use RFILE's group rather than specifying a GROUP. RFILE is always dereferenced if a symbolic link. -R, --recursive operate on files and directories recursively The following options modify how a hierarchy is traversed when the -R option is also specified. If more than one is specified, only the final one takes effect. -H if a command line argument is a symbolic link to a directory, traverse it -L traverse every symbolic link to a directory encountered -P do not traverse any symbolic links (default) --help display this help and exit --version output version information and exit EXAMPLES top chgrp staff /u Change the group of /u to "staff". chgrp -hR staff /u Change the group of /u and subfiles to "staff". AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chown(1), chown(2) Full documentation <https://www.gnu.org/software/coreutils/chgrp> or available locally via: info '(coreutils) chgrp invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CHGRP(1) Pages that refer to this page: chown(2), group(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes the group of defined file. Bash Command:<START>chgrp<END>

Changes to the directory where 'ssh' executable is located.

cd $(dirname $(which ssh));

['dirname', 'cd', 'ssh']

Output a Bash command to accomplish the following task. Task: Changes to the directory where 'ssh' executable is located. Bash Command:<START>cd $(dirname $(which ssh));<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # dirname\n\n> Calculates the parent directory of a file or directory path.\n> More information: <https://www.gnu.org/software/coreutils/dirname>.\n\n- Calculate the parent directory of a given path:\n\n`dirname {{path/to/file_or_directory}}`\n\n- Calculate the parent directory of multiple paths:\n\n`dirname {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n\n- Delimit output with a NUL character instead of a newline (useful when combining with `xargs`):\n\n`dirname --zero {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n # cd\n\n> Change the current working directory.\n> More information: <https://manned.org/cd>.\n\n- Go to the specified directory:\n\n`cd {{path/to/directory}}`\n\n- Go up to the parent of the current directory:\n\n`cd ..`\n\n- Go to the home directory of the current user:\n\n`cd`\n\n- Go to the home directory of the specified user:\n\n`cd ~{{username}}`\n\n- Go to the previously chosen directory:\n\n`cd -`\n\n- Go to the root directory:\n\n`cd /`\n # ssh\n\n> Secure Shell is a protocol used to securely log onto remote systems.\n> It can be used for logging or executing commands on a remote server.\n> More information: <https://man.openbsd.org/ssh>.\n\n- Connect to a remote server:\n\n`ssh {{username}}@{{remote_host}}`\n\n- Connect to a remote server with a specific identity (private key):\n\n`ssh -i {{path/to/key_file}} {{username}}@{{remote_host}}`\n\n- Connect to a remote server using a specific [p]ort:\n\n`ssh {{username}}@{{remote_host}} -p {{2222}}`\n\n- Run a command on a remote server with a [t]ty allocation allowing interaction with the remote command:\n\n`ssh {{username}}@{{remote_host}} -t {{command}} {{command_arguments}}`\n\n- SSH tunneling: [D]ynamic port forwarding (SOCKS proxy on `localhost:1080`):\n\n`ssh -D {{1080}} {{username}}@{{remote_host}}`\n\n- SSH tunneling: Forward a specific port (`localhost:9999` to `example.org:80`) along with disabling pseudo-[T]ty allocation and executio[N] of remote commands:\n\n`ssh -L {{9999}}:{{example.org}}:{{80}} -N -T {{username}}@{{remote_host}}`\n\n- SSH [J]umping: Connect through a jumphost to a remote server (Multiple jump hops may be specified separated by comma characters):\n\n`ssh -J {{username}}@{{jump_host}} {{username}}@{{remote_host}}`\n\n- Agent forwarding: Forward the authentication information to the remote machine (see `man ssh_config` for available options):\n\n`ssh -A {{username}}@{{remote_host}}`\n Task: Changes to the directory where 'ssh' executable is located. Bash Command:<START>cd $(dirname $(which ssh));<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: dirname(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training dirname(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIRNAME(1) User Commands DIRNAME(1) NAME top dirname - strip last component from file name SYNOPSIS top dirname [OPTION] NAME... DESCRIPTION top Output each NAME with its last non-slash component and trailing slashes removed; if NAME contains no /'s, output '.' (meaning the current directory). -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit EXAMPLES top dirname /usr/bin/ -> "/usr" dirname dir1/str dir2/str -> "dir1" followed by "dir2" dirname stdio.h -> "." AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top basename(1), readlink(1) Full documentation <https://www.gnu.org/software/coreutils/dirname> or available locally via: info '(coreutils) dirname invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DIRNAME(1) Pages that refer to this page: basename(1), basename(3) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. cd(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cd(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT CD(1P) POSIX Programmer's Manual CD(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top cd change the working directory SYNOPSIS top cd [-L|-P] [directory] cd - DESCRIPTION top The cd utility shall change the working directory of the current shell execution environment (see Section 2.12, Shell Execution Environment) by executing the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to simplify the description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.) 1. If no directory operand is given and the HOME environment variable is empty or undefined, the default behavior is implementation-defined and no further steps shall be taken. 2. If no directory operand is given and the HOME environment variable is set to a non-empty value, the cd utility shall behave as if the directory named in the HOME environment variable was specified as the directory operand. 3. If the directory operand begins with a <slash> character, set curpath to the operand and proceed to step 7. 4. If the first component of the directory operand is dot or dot-dot, proceed to step 6. 5. Starting with the first pathname in the <colon>-separated pathnames of CDPATH (see the ENVIRONMENT VARIABLES section) if the pathname is non-null, test if the concatenation of that pathname, a <slash> character if that pathname did not end with a <slash> character, and the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the operand names a directory. In either case, if the resulting string names an existing directory, set curpath to that string and proceed to step 7. Otherwise, repeat this step with the next pathname in CDPATH until all pathnames have been tested. 6. Set curpath to the directory operand. 7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath. 8. The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: a. Dot components and any <slash> characters that separate them from the next component shall be deleted. b. For each dot-dot component, if there is a preceding component and it is neither root nor dot-dot, then: i. If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory, then the cd utility shall display an appropriate error message and no further steps shall be taken. ii. The preceding component, all <slash> characters separating the preceding component from dot-dot, dot-dot, and all <slash> characters separating dot- dot from the following component (if any) shall be deleted. c. An implementation may further simplify curpath by removing any trailing <slash> characters that are not also leading <slash> characters, replacing multiple non- leading consecutive <slash> characters with a single <slash>, and replacing three or more leading <slash> characters with a single <slash>. If, as a result of this canonicalization, the curpath variable is null, no further steps shall be taken. 9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not longer than {PATH_MAX} bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already have one, is an initial substring of curpath. Whether or not it is considered possible under other circumstances is unspecified. Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer than {PATH_MAX} bytes. 10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If the -P option is not in effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e., before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string that would be output by pwd -P. If there is insufficient permission on the new directory, or on any parent of that directory, to determine the current working directory, the value of the PWD environment variable is unspecified. If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set to the value of the old working directory (that is the current working directory immediately prior to the call to cd). OPTIONS top The cd utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation: -L Handle the operand dot-dot logically; symbolic link components shall not be resolved before dot-dot components are processed (see steps 8. and 9. in the DESCRIPTION). -P Handle the operand dot-dot physically; symbolic link components shall be resolved before dot-dot components are processed (see step 7. in the DESCRIPTION). If both -L and -P options are specified, the last of these options shall be used and all others ignored. If neither -L nor -P is specified, the operand shall be handled dot-dot logically; see the DESCRIPTION. OPERANDS top The following operands shall be supported: directory An absolute or relative pathname of the directory that shall become the new working directory. The interpretation of a relative pathname by cd depends on the -L option and the CDPATH and PWD environment variables. If directory is an empty string, the results are unspecified. - When a <hyphen-minus> is used as the operand, this shall be equivalent to the command: cd "$OLDPWD" && pwd which changes to the previous working directory and then writes its name. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of cd: CDPATH A <colon>-separated list of pathnames that refer to directories. The cd utility shall use this list in its attempt to change the directory, as described in the DESCRIPTION. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it shall be treated as if it were an empty string. HOME The name of the directory, used when no directory operand is specified. LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. OLDPWD A pathname of the previous working directory, used by cd -. PWD This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD, the behavior of cd is unspecified. ASYNCHRONOUS EVENTS top Default. STDOUT top If a non-empty directory name from CDPATH is used, or if cd - is used, an absolute pathname of the new working directory shall be written to the standard output as follows: "%s\n", <new directory> Otherwise, there shall be no output. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The following exit values shall be returned: 0 The directory was successfully changed. >0 An error occurred. CONSEQUENCES OF ERRORS top The working directory shall remain unchanged. The following sections are informative. APPLICATION USAGE top Since cd affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a subshell or separate utility execution environment, such as one of the following: (cd /tmp) nohup cd find . -exec cd {} \; it does not affect the working directory of the caller's environment. The user must have execute (search) permission in directory in order to change to it. EXAMPLES top The following template can be used to perform processing in the directory specified by location and end up in the current working directory in use before the first cd command was issued: cd location if [ $? -ne 0 ] then print error message exit 1 fi ... do whatever is desired as long as the OLDPWD environment variable is not modified cd - RATIONALE top The use of the CDPATH was introduced in the System V shell. Its use is analogous to the use of the PATH variable in the shell. The BSD C shell used a shell parameter cdpath for this purpose. A common extension when HOME is undefined is to get the login directory from the user database for the invoking user. This does not occur on System V implementations. Some historical shells, such as the KornShell, took special actions when the directory name contained a dot-dot component, selecting the logical parent of the directory, rather than the actual parent directory; that is, it moved up one level toward the '/' in the pathname, remembering what the user typed, rather than performing the equivalent of: chdir(".."); In such a shell, the following commands would not necessarily produce equivalent output for all directories: cd .. && ls ls .. This behavior is now the default. It is not consistent with the definition of dot-dot in most historical practice; that is, while this behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical pathname is stored in the PWD environment variable when the cd utility completes and this value is used to construct the next directory name if cd is invoked with the -L option. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.12, Shell Execution Environment, pwd(1p) The Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, chdir(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 CD(1P) Pages that refer to this page: pwd(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. ssh(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training ssh(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHENTICATION | ESCAPE CHARACTERS | TCP FORWARDING | X11 FORWARDING | VERIFYING HOST KEYS | SSH-BASED VIRTUAL PRIVATE NETWORKS | ENVIRONMENT | FILES | EXIT STATUS | SEE ALSO | STANDARDS | AUTHORS | COLOPHON SSH(1) General Commands Manual SSH(1) NAME top ssh OpenSSH remote login client SYNOPSIS top ssh [-46AaCfGgKkMNnqsTtVvXxYy] [-B bind_interface] [-b bind_address] [-c cipher_spec] [-D [bind_address:]port] [-E log_file] [-e escape_char] [-F configfile] [-I pkcs11] [-i identity_file] [-J destination] [-L address] [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-P tag] [-p port] [-R address] [-S ctl_path] [-W host:port] [-w local_tun[:remote_tun]] destination [command [argument ...]] [-Q query_option] DESCRIPTION top (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine. It is intended to provide secure encrypted communications between two untrusted hosts over an insecure network. X11 connections, arbitrary TCP ports and Unix-domain sockets can also be forwarded over the secure channel. connects and logs into the specified destination, which may be specified as either [user@]hostname or a URI of the form ssh://[user@]hostname[:port]. The user must prove their identity to the remote machine using one of several methods (see below). If a command is specified, it will be executed on the remote host instead of a login shell. A complete command line may be specified as command, or it may have additional arguments. If supplied, the arguments will be appended to the command, separated by spaces, before it is sent to the server to be executed. The options are as follows: -4 Forces to use IPv4 addresses only. -6 Forces to use IPv6 addresses only. -A Enables forwarding of connections from an authentication agent such as ssh-agent(1). This can also be specified on a per-host basis in a configuration file. Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the agent's Unix-domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. A safer alternative may be to use a jump host (see -J). -a Disables forwarding of the authentication agent connection. -B bind_interface Bind to the address of bind_interface before attempting to connect to the destination host. This is only useful on systems with more than one address. -b bind_address Use bind_address on the local machine as the source address of the connection. Only useful on systems with more than one address. -C Requests compression of all data (including stdin, stdout, stderr, and data for forwarded X11, TCP and Unix-domain connections). The compression algorithm is the same used by gzip(1). Compression is desirable on modem lines and other slow connections, but will only slow down things on fast networks. The default value can be set on a host-by-host basis in the configuration files; see the Compression option in ssh_config(5). -c cipher_spec Selects the cipher specification for encrypting the session. cipher_spec is a comma-separated list of ciphers listed in order of preference. See the Ciphers keyword in ssh_config(5) for more information. -D [bind_address:]port Specifies a local dynamic application-level port forwarding. This works by allocating a socket to listen to port on the local side, optionally bound to the specified bind_address. Whenever a connection is made to this port, the connection is forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. Currently the SOCKS4 and SOCKS5 protocols are supported, and will act as a SOCKS server. Only root can forward privileged ports. Dynamic port forwardings can also be specified in the configuration file. IPv6 addresses can be specified by enclosing the address in square brackets. Only the superuser can forward privileged ports. By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address of localhost indicates that the listening port be bound for local use only, while an empty address or * indicates that the port should be available from all interfaces. -E log_file Append debug logs to log_file instead of standard error. -e escape_char Sets the escape character for sessions with a pty (default: ~). The escape character is only recognized at the beginning of a line. The escape character followed by a dot (.) closes the connection; followed by control-Z suspends the connection; and followed by itself sends the escape character once. Setting the character to none disables any escapes and makes the session fully transparent. -F configfile Specifies an alternative per-user configuration file. If a configuration file is given on the command line, the system-wide configuration file (/etc/ssh/ssh_config) will be ignored. The default for the per-user configuration file is ~/.ssh/config. If set to none, no configuration files will be read. -f Requests to go to background just before command execution. This is useful if is going to ask for passwords or passphrases, but the user wants it in the background. This implies -n. The recommended way to start X11 programs at a remote site is with something like ssh -f host xterm. If the ExitOnForwardFailure configuration option is set to yes, then a client started with -f will wait for all remote port forwards to be successfully established before placing itself in the background. Refer to the description of ForkAfterAuthentication in ssh_config(5) for details. -G Causes to print its configuration after evaluating Host and Match blocks and exit. -g Allows remote hosts to connect to local forwarded ports. If used on a multiplexed connection, then this option must be specified on the master process. -I pkcs11 Specify the PKCS#11 shared library should use to communicate with a PKCS#11 token providing keys for user authentication. -i identity_file Selects a file from which the identity (private key) for public key authentication is read. You can also specify a public key file to use the corresponding private key that is loaded in ssh-agent(1) when the private key file is not present locally. The default is ~/.ssh/id_rsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ecdsa_sk, ~/.ssh/id_ed25519, ~/.ssh/id_ed25519_sk and ~/.ssh/id_dsa. Identity files may also be specified on a per-host basis in the configuration file. It is possible to have multiple -i options (and multiple identities specified in configuration files). If no certificates have been explicitly specified by the CertificateFile directive, will also try to load certificate information from the filename obtained by appending -cert.pub to identity filenames. -J destination Connect to the target host by first making an connection to the jump host described by destination and then establishing a TCP forwarding to the ultimate destination from there. Multiple jump hops may be specified separated by comma characters. This is a shortcut to specify a ProxyJump configuration directive. Note that configuration directives supplied on the command-line generally apply to the destination host and not any specified jump hosts. Use ~/.ssh/config to specify configuration for jump hosts. -K Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI credentials to the server. -k Disables forwarding (delegation) of GSSAPI credentials to the server. -L [bind_address:]port:host:hostport -L [bind_address:]port:remote_socket -L local_socket:host:hostport -L local_socket:remote_socket Specifies that connections to the given TCP port or Unix socket on the local (client) host are to be forwarded to the given host and port, or Unix socket, on the remote side. This works by allocating a socket to listen to either a TCP port on the local side, optionally bound to the specified bind_address, or to a Unix socket. Whenever a connection is made to the local port or socket, the connection is forwarded over the secure channel, and a connection is made to either host port hostport, or the Unix socket remote_socket, from the remote machine. Port forwardings can also be specified in the configuration file. Only the superuser can forward privileged ports. IPv6 addresses can be specified by enclosing the address in square brackets. By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address of localhost indicates that the listening port be bound for local use only, while an empty address or * indicates that the port should be available from all interfaces. -l login_name Specifies the user to log in as on the remote machine. This also may be specified on a per-host basis in the configuration file. -M Places the client into master mode for connection sharing. Multiple -M options places into master mode but with confirmation required using ssh-askpass(1) before each operation that changes the multiplexing state (e.g. opening a new session). Refer to the description of ControlMaster in ssh_config(5) for details. -m mac_spec A comma-separated list of MAC (message authentication code) algorithms, specified in order of preference. See the MACs keyword in ssh_config(5) for more information. -N Do not execute a remote command. This is useful for just forwarding ports. Refer to the description of SessionType in ssh_config(5) for details. -n Redirects stdin from /dev/null (actually, prevents reading from stdin). This must be used when is run in the background. A common trick is to use this to run X11 programs on a remote machine. For example, ssh -n shadows.cs.hut.fi emacs & will start an emacs on shadows.cs.hut.fi, and the X11 connection will be automatically forwarded over an encrypted channel. The program will be put in the background. (This does not work if needs to ask for a password or passphrase; see also the -f option.) Refer to the description of StdinNull in ssh_config(5) for details. -O ctl_cmd Control an active connection multiplexing master process. When the -O option is specified, the ctl_cmd argument is interpreted and passed to the master process. Valid commands are: check (check that the master process is running), forward (request forwardings without command execution), cancel (cancel forwardings), exit (request the master to exit), and stop (request the master to stop accepting further multiplexing requests). -o option Can be used to give options in the format used in the configuration file. This is useful for specifying options for which there is no separate command-line flag. For full details of the options listed below, and their possible values, see ssh_config(5). AddKeysToAgent AddressFamily BatchMode BindAddress CanonicalDomains CanonicalizeFallbackLocal CanonicalizeHostname CanonicalizeMaxDots CanonicalizePermittedCNAMEs CASignatureAlgorithms CertificateFile CheckHostIP Ciphers ClearAllForwardings Compression ConnectionAttempts ConnectTimeout ControlMaster ControlPath ControlPersist DynamicForward EnableEscapeCommandline EscapeChar ExitOnForwardFailure FingerprintHash ForkAfterAuthentication ForwardAgent ForwardX11 ForwardX11Timeout ForwardX11Trusted GatewayPorts GlobalKnownHostsFile GSSAPIAuthentication GSSAPIDelegateCredentials HashKnownHosts Host HostbasedAcceptedAlgorithms HostbasedAuthentication HostKeyAlgorithms HostKeyAlias Hostname IdentitiesOnly IdentityAgent IdentityFile IPQoS KbdInteractiveAuthentication KbdInteractiveDevices KexAlgorithms KnownHostsCommand LocalCommand LocalForward LogLevel MACs Match NoHostAuthenticationForLocalhost NumberOfPasswordPrompts PasswordAuthentication PermitLocalCommand PermitRemoteOpen PKCS11Provider Port PreferredAuthentications ProxyCommand ProxyJump ProxyUseFdpass PubkeyAcceptedAlgorithms PubkeyAuthentication RekeyLimit RemoteCommand RemoteForward RequestTTY RequiredRSASize SendEnv ServerAliveInterval ServerAliveCountMax SessionType SetEnv StdinNull StreamLocalBindMask StreamLocalBindUnlink StrictHostKeyChecking TCPKeepAlive Tunnel TunnelDevice UpdateHostKeys User UserKnownHostsFile VerifyHostKeyDNS VisualHostKey XAuthLocation -P tag Specify a tag name that may be used to select configuration in ssh_config(5). Refer to the Tag and Match keywords in ssh_config(5) for more information. -p port Port to connect to on the remote host. This can be specified on a per-host basis in the configuration file. -Q query_option Queries for the algorithms supported by one of the following features: cipher (supported symmetric ciphers), cipher-auth (supported symmetric ciphers that support authenticated encryption), help (supported query terms for use with the -Q flag), mac (supported message integrity codes), kex (key exchange algorithms), key (key types), key-ca-sign (valid CA signature algorithms for certificates), key-cert (certificate key types), key-plain (non-certificate key types), key-sig (all key types and signature algorithms), protocol-version (supported SSH protocol versions), and sig (supported signature algorithms). Alternatively, any keyword from ssh_config(5) or sshd_config(5) that takes an algorithm list may be used as an alias for the corresponding query_option. -q Quiet mode. Causes most warning and diagnostic messages to be suppressed. -R [bind_address:]port:host:hostport -R [bind_address:]port:local_socket -R remote_socket:host:hostport -R remote_socket:local_socket -R [bind_address:]port Specifies that connections to the given TCP port or Unix socket on the remote (server) host are to be forwarded to the local side. This works by allocating a socket to listen to either a TCP port or to a Unix socket on the remote side. Whenever a connection is made to this port or Unix socket, the connection is forwarded over the secure channel, and a connection is made from the local machine to either an explicit destination specified by host port hostport, or local_socket, or, if no explicit destination was specified, will act as a SOCKS 4/5 proxy and forward connections to the destinations requested by the remote SOCKS client. Port forwardings can also be specified in the configuration file. Privileged ports can be forwarded only when logging in as root on the remote machine. IPv6 addresses can be specified by enclosing the address in square brackets. By default, TCP listening sockets on the server will be bound to the loopback interface only. This may be overridden by specifying a bind_address. An empty bind_address, or the address *, indicates that the remote socket should listen on all interfaces. Specifying a remote bind_address will only succeed if the server's GatewayPorts option is enabled (see sshd_config(5)). If the port argument is 0, the listen port will be dynamically allocated on the server and reported to the client at run time. When used together with -O forward, the allocated port will be printed to the standard output. -S ctl_path Specifies the location of a control socket for connection sharing, or the string none to disable connection sharing. Refer to the description of ControlPath and ControlMaster in ssh_config(5) for details. -s May be used to request invocation of a subsystem on the remote system. Subsystems facilitate the use of SSH as a secure transport for other applications (e.g. sftp(1)). The subsystem is specified as the remote command. Refer to the description of SessionType in ssh_config(5) for details. -T Disable pseudo-terminal allocation. -t Force pseudo-terminal allocation. This can be used to execute arbitrary screen-based programs on a remote machine, which can be very useful, e.g. when implementing menu services. Multiple -t options force tty allocation, even if has no local tty. -V Display the version number and exit. -v Verbose mode. Causes to print debugging messages about its progress. This is helpful in debugging connection, authentication, and configuration problems. Multiple -v options increase the verbosity. The maximum is 3. -W host:port Requests that standard input and output on the client be forwarded to host on port over the secure channel. Implies -N, -T, ExitOnForwardFailure and ClearAllForwardings, though these can be overridden in the configuration file or using -o command line options. -w local_tun[:remote_tun] Requests tunnel device forwarding with the specified tun(4) devices between the client (local_tun) and the server (remote_tun). The devices may be specified by numerical ID or the keyword any, which uses the next available tunnel device. If remote_tun is not specified, it defaults to any. See also the Tunnel and TunnelDevice directives in ssh_config(5). If the Tunnel directive is unset, it will be set to the default tunnel mode, which is point-to-point. If a different Tunnel forwarding mode it desired, then it should be specified before -w. -X Enables X11 forwarding. This can also be specified on a per-host basis in a configuration file. X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user's X authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring. For this reason, X11 forwarding is subjected to X11 SECURITY extension restrictions by default. Refer to the -Y option and the ForwardX11Trusted directive in ssh_config(5) for more information. -x Disables X11 forwarding. -Y Enables trusted X11 forwarding. Trusted X11 forwardings are not subjected to the X11 SECURITY extension controls. -y Send log information using the syslog(3) system module. By default this information is sent to stderr. may additionally obtain configuration data from a per-user configuration file and a system-wide configuration file. The file format and configuration options are described in ssh_config(5). AUTHENTICATION top The OpenSSH SSH client supports SSH protocol 2. The methods available for authentication are: GSSAPI-based authentication, host-based authentication, public key authentication, keyboard-interactive authentication, and password authentication. Authentication methods are tried in the order specified above, though PreferredAuthentications can be used to change the default order. Host-based authentication works as follows: If the machine the user logs in from is listed in /etc/hosts.equiv or /etc/shosts.equiv on the remote machine, the user is non-root and the user names are the same on both sides, or if the files ~/.rhosts or ~/.shosts exist in the user's home directory on the remote machine and contain a line containing the name of the client machine and the name of the user on that machine, the user is considered for login. Additionally, the server must be able to verify the client's host key (see the description of /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts, below) for login to be permitted. This authentication method closes security holes due to IP spoofing, DNS spoofing, and routing spoofing. [Note to the administrator: /etc/hosts.equiv, ~/.rhosts, and the rlogin/rsh protocol in general, are inherently insecure and should be disabled if security is desired.] Public key authentication works as follows: The scheme is based on public-key cryptography, using cryptosystems where encryption and decryption are done using separate keys, and it is unfeasible to derive the decryption key from the encryption key. The idea is that each user creates a public/private key pair for authentication purposes. The server knows the public key, and only the user knows the private key. implements public key authentication protocol automatically, using one of the DSA, ECDSA, Ed25519 or RSA algorithms. The HISTORY section of ssl(8) contains a brief discussion of the DSA and RSA algorithms. The file ~/.ssh/authorized_keys lists the public keys that are permitted for logging in. When the user logs in, the program tells the server which key pair it would like to use for authentication. The client proves that it has access to the private key and the server checks that the corresponding public key is authorized to accept the account. The server may inform the client of errors that prevented public key authentication from succeeding after authentication completes using a different method. These may be viewed by increasing the LogLevel to DEBUG or higher (e.g. by using the -v flag). The user creates their key pair by running ssh-keygen(1). This stores the private key in ~/.ssh/id_dsa (DSA), ~/.ssh/id_ecdsa (ECDSA), ~/.ssh/id_ecdsa_sk (authenticator-hosted ECDSA), ~/.ssh/id_ed25519 (Ed25519), ~/.ssh/id_ed25519_sk (authenticator- hosted Ed25519), or ~/.ssh/id_rsa (RSA) and stores the public key in ~/.ssh/id_dsa.pub (DSA), ~/.ssh/id_ecdsa.pub (ECDSA), ~/.ssh/id_ecdsa_sk.pub (authenticator-hosted ECDSA), ~/.ssh/id_ed25519.pub (Ed25519), ~/.ssh/id_ed25519_sk.pub (authenticator-hosted Ed25519), or ~/.ssh/id_rsa.pub (RSA) in the user's home directory. The user should then copy the public key to ~/.ssh/authorized_keys in their home directory on the remote machine. The authorized_keys file corresponds to the conventional ~/.rhosts file, and has one key per line, though the lines can be very long. After this, the user can log in without giving the password. A variation on public key authentication is available in the form of certificate authentication: instead of a set of public/private keys, signed certificates are used. This has the advantage that a single trusted certification authority can be used in place of many public/private keys. See the CERTIFICATES section of ssh-keygen(1) for more information. The most convenient way to use public key or certificate authentication may be with an authentication agent. See ssh-agent(1) and (optionally) the AddKeysToAgent directive in ssh_config(5) for more information. Keyboard-interactive authentication works as follows: The server sends an arbitrary "challenge" text and prompts for a response, possibly multiple times. Examples of keyboard-interactive authentication include BSD Authentication (see login.conf(5)) and PAM (some non-OpenBSD systems). Finally, if other authentication methods fail, prompts the user for a password. The password is sent to the remote host for checking; however, since all communications are encrypted, the password cannot be seen by someone listening on the network. automatically maintains and checks a database containing identification for all hosts it has ever been used with. Host keys are stored in ~/.ssh/known_hosts in the user's home directory. Additionally, the file /etc/ssh/ssh_known_hosts is automatically checked for known hosts. Any new hosts are automatically added to the user's file. If a host's identification ever changes, warns about this and disables password authentication to prevent server spoofing or man-in-the- middle attacks, which could otherwise be used to circumvent the encryption. The StrictHostKeyChecking option can be used to control logins to machines whose host key is not known or has changed. When the user's identity has been accepted by the server, the server either executes the given command in a non-interactive session or, if no command has been specified, logs into the machine and gives the user a normal shell as an interactive session. All communication with the remote command or shell will be automatically encrypted. If an interactive session is requested, by default will only request a pseudo-terminal (pty) for interactive sessions when the client has one. The flags -T and -t can be used to override this behaviour. If a pseudo-terminal has been allocated, the user may use the escape characters noted below. If no pseudo-terminal has been allocated, the session is transparent and can be used to reliably transfer binary data. On most systems, setting the escape character to none will also make the session transparent even if a tty is used. The session terminates when the command or shell on the remote machine exits and all X11 and TCP connections have been closed. ESCAPE CHARACTERS top When a pseudo-terminal has been requested, supports a number of functions through the use of an escape character. A single tilde character can be sent as ~~ or by following the tilde by a character other than those described below. The escape character must always follow a newline to be interpreted as special. The escape character can be changed in configuration files using the EscapeChar configuration directive or on the command line by the -e option. The supported escapes (assuming the default ~) are: ~. Disconnect. ~^Z Background . ~# List forwarded connections. ~& Background at logout when waiting for forwarded connection / X11 sessions to terminate. ~? Display a list of escape characters. ~B Send a BREAK to the remote system (only useful if the peer supports it). ~C Open command line. Currently this allows the addition of port forwardings using the -L, -R and -D options (see above). It also allows the cancellation of existing port-forwardings with -KL[bind_address:]port for local, -KR[bind_address:]port for remote and -KD[bind_address:]port for dynamic port-forwardings. !command allows the user to execute a local command if the PermitLocalCommand option is enabled in ssh_config(5). Basic help is available, using the -h option. ~R Request rekeying of the connection (only useful if the peer supports it). ~V Decrease the verbosity (LogLevel) when errors are being written to stderr. ~v Increase the verbosity (LogLevel) when errors are being written to stderr. TCP FORWARDING top Forwarding of arbitrary TCP connections over a secure channel can be specified either on the command line or in a configuration file. One possible application of TCP forwarding is a secure connection to a mail server; another is going through firewalls. In the example below, we look at encrypting communication for an IRC client, even though the IRC server it connects to does not directly support encrypted communication. This works as follows: the user connects to the remote host using , specifying the ports to be used to forward the connection. After that it is possible to start the program locally, and will encrypt and forward the connection to the remote server. The following example tunnels an IRC session from the client to an IRC server at server.example.com, joining channel #users, nickname pinky, using the standard IRC port, 6667: $ ssh -f -L 6667:localhost:6667 server.example.com sleep 10 $ irc -c '#users' pinky IRC/127.0.0.1 The -f option backgrounds and the remote command sleep 10 is specified to allow an amount of time (10 seconds, in the example) to start the program which is going to use the tunnel. If no connections are made within the time specified, will exit. X11 FORWARDING top If the ForwardX11 variable is set to yes (or see the description of the -X, -x, and -Y options above) and the user is using X11 (the DISPLAY environment variable is set), the connection to the X11 display is automatically forwarded to the remote side in such a way that any X11 programs started from the shell (or command) will go through the encrypted channel, and the connection to the real X server will be made from the local machine. The user should not manually set DISPLAY. Forwarding of X11 connections can be configured on the command line or in configuration files. The DISPLAY value set by will point to the server machine, but with a display number greater than zero. This is normal, and happens because creates a proxy X server on the server machine for forwarding the connections over the encrypted channel. will also automatically set up Xauthority data on the server machine. For this purpose, it will generate a random authorization cookie, store it in Xauthority on the server, and verify that any forwarded connections carry this cookie and replace it by the real cookie when the connection is opened. The real authentication cookie is never sent to the server machine (and no cookies are sent in the plain). If the ForwardAgent variable is set to yes (or see the description of the -A and -a options above) and the user is using an authentication agent, the connection to the agent is automatically forwarded to the remote side. VERIFYING HOST KEYS top When connecting to a server for the first time, a fingerprint of the server's public key is presented to the user (unless the option StrictHostKeyChecking has been disabled). Fingerprints can be determined using ssh-keygen(1): $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key If the fingerprint is already known, it can be matched and the key can be accepted or rejected. If only legacy (MD5) fingerprints for the server are available, the ssh-keygen(1) -E option may be used to downgrade the fingerprint algorithm to match. Because of the difficulty of comparing host keys just by looking at fingerprint strings, there is also support to compare host keys visually, using random art. By setting the VisualHostKey option to yes, a small ASCII graphic gets displayed on every login to a server, no matter if the session itself is interactive or not. By learning the pattern a known server produces, a user can easily find out that the host key has changed when a completely different pattern is displayed. Because these patterns are not unambiguous however, a pattern that looks similar to the pattern remembered only gives a good probability that the host key is the same, not guaranteed proof. To get a listing of the fingerprints along with their random art for all known hosts, the following command line can be used: $ ssh-keygen -lv -f ~/.ssh/known_hosts If the fingerprint is unknown, an alternative method of verification is available: SSH fingerprints verified by DNS. An additional resource record (RR), SSHFP, is added to a zonefile and the connecting client is able to match the fingerprint with that of the key presented. In this example, we are connecting a client to a server, host.example.com. The SSHFP resource records should first be added to the zonefile for host.example.com: $ ssh-keygen -r host.example.com. The output lines will have to be added to the zonefile. To check that the zone is answering fingerprint queries: $ dig -t SSHFP host.example.com Finally the client connects: $ ssh -o "VerifyHostKeyDNS ask" host.example.com [...] Matching host key fingerprint found in DNS. Are you sure you want to continue connecting (yes/no)? See the VerifyHostKeyDNS option in ssh_config(5) for more information. SSH-BASED VIRTUAL PRIVATE NETWORKS top contains support for Virtual Private Network (VPN) tunnelling using the tun(4) network pseudo-device, allowing two networks to be joined securely. The sshd_config(5) configuration option PermitTunnel controls whether the server supports this, and at what level (layer 2 or 3 traffic). The following example would connect client network 10.0.50.0/24 with remote network 10.0.99.0/24 using a point-to-point connection from 10.1.1.1 to 10.1.1.2, provided that the SSH server running on the gateway to the remote network, at 192.168.1.15, allows it. On the client: # ssh -f -w 0:1 192.168.1.15 true # ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252 # route add 10.0.99.0/24 10.1.1.2 On the server: # ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252 # route add 10.0.50.0/24 10.1.1.1 Client access may be more finely tuned via the /root/.ssh/authorized_keys file (see below) and the PermitRootLogin server option. The following entry would permit connections on tun(4) device 1 from user jane and on tun device 2 from user john, if PermitRootLogin is set to forced-commands-only: tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john Since an SSH-based setup entails a fair amount of overhead, it may be more suited to temporary setups, such as for wireless VPNs. More permanent VPNs are better provided by tools such as ipsecctl(8) and isakmpd(8). ENVIRONMENT top will normally set the following environment variables: DISPLAY The DISPLAY variable indicates the location of the X11 server. It is automatically set by to point to a value of the form hostname:n, where hostname indicates the host where the shell runs, and n is an integer 1. uses this special value to forward X11 connections over the secure channel. The user should normally not set DISPLAY explicitly, as that will render the X11 connection insecure (and will require the user to manually copy any required authorization cookies). HOME Set to the path of the user's home directory. LOGNAME Synonym for USER; set for compatibility with systems that use this variable. MAIL Set to the path of the user's mailbox. PATH Set to the default PATH, as specified when compiling . SSH_ASKPASS If needs a passphrase, it will read the passphrase from the current terminal if it was run from a terminal. If does not have a terminal associated with it but DISPLAY and SSH_ASKPASS are set, it will execute the program specified by SSH_ASKPASS and open an X11 window to read the passphrase. This is particularly useful when calling from a .xsession or related script. (Note that on some machines it may be necessary to redirect the input from /dev/null to make this work.) SSH_ASKPASS_REQUIRE Allows further control over the use of an askpass program. If this variable is set to never then will never attempt to use one. If it is set to prefer, then will prefer to use the askpass program instead of the TTY when requesting passwords. Finally, if the variable is set to force, then the askpass program will be used for all passphrase input regardless of whether DISPLAY is set. SSH_AUTH_SOCK Identifies the path of a Unix-domain socket used to communicate with the agent. SSH_CONNECTION Identifies the client and server ends of the connection. The variable contains four space-separated values: client IP address, client port number, server IP address, and server port number. SSH_ORIGINAL_COMMAND This variable contains the original command line if a forced command is executed. It can be used to extract the original arguments. SSH_TTY This is set to the name of the tty (path to the device) associated with the current shell or command. If the current session has no tty, this variable is not set. SSH_TUNNEL Optionally set by sshd(8) to contain the interface names assigned if tunnel forwarding was requested by the client. SSH_USER_AUTH Optionally set by sshd(8), this variable may contain a pathname to a file that lists the authentication methods successfully used when the session was established, including any public keys that were used. TZ This variable is set to indicate the present time zone if it was set when the daemon was started (i.e. the daemon passes the value on to new connections). USER Set to the name of the user logging in. Additionally, reads ~/.ssh/environment, and adds lines of the format VARNAME=value to the environment if the file exists and users are allowed to change their environment. For more information, see the PermitUserEnvironment option in sshd_config(5). FILES top ~/.rhosts This file is used for host-based authentication (see above). On some machines this file may need to be world- readable if the user's home directory is on an NFS partition, because sshd(8) reads it as root. Additionally, this file must be owned by the user, and must not have write permissions for anyone else. The recommended permission for most machines is read/write for the user, and not accessible by others. ~/.shosts This file is used in exactly the same way as .rhosts, but allows host-based authentication without permitting login with rlogin/rsh. ~/.ssh/ This directory is the default location for all user- specific configuration and authentication information. There is no general requirement to keep the entire contents of this directory secret, but the recommended permissions are read/write/execute for the user, and not accessible by others. ~/.ssh/authorized_keys Lists the public keys (DSA, ECDSA, Ed25519, RSA) that can be used for logging in as this user. The format of this file is described in the sshd(8) manual page. This file is not highly sensitive, but the recommended permissions are read/write for the user, and not accessible by others. ~/.ssh/config This is the per-user configuration file. The file format and configuration options are described in ssh_config(5). Because of the potential for abuse, this file must have strict permissions: read/write for the user, and not writable by others. ~/.ssh/environment Contains additional definitions for environment variables; see ENVIRONMENT, above. ~/.ssh/id_dsa ~/.ssh/id_ecdsa ~/.ssh/id_ecdsa_sk ~/.ssh/id_ed25519 ~/.ssh/id_ed25519_sk ~/.ssh/id_rsa Contains the private key for authentication. These files contain sensitive data and should be readable by the user but not accessible by others (read/write/execute). will simply ignore a private key file if it is accessible by others. It is possible to specify a passphrase when generating the key which will be used to encrypt the sensitive part of this file using AES-128. ~/.ssh/id_dsa.pub ~/.ssh/id_ecdsa.pub ~/.ssh/id_ecdsa_sk.pub ~/.ssh/id_ed25519.pub ~/.ssh/id_ed25519_sk.pub ~/.ssh/id_rsa.pub Contains the public key for authentication. These files are not sensitive and can (but need not) be readable by anyone. ~/.ssh/known_hosts Contains a list of host keys for all hosts the user has logged into that are not already in the systemwide list of known host keys. See sshd(8) for further details of the format of this file. ~/.ssh/rc Commands in this file are executed by when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information. /etc/hosts.equiv This file is for host-based authentication (see above). It should only be writable by root. /etc/shosts.equiv This file is used in exactly the same way as hosts.equiv, but allows host-based authentication without permitting login with rlogin/rsh. /etc/ssh/ssh_config Systemwide configuration file. The file format and configuration options are described in ssh_config(5). /etc/ssh/ssh_host_key /etc/ssh/ssh_host_dsa_key /etc/ssh/ssh_host_ecdsa_key /etc/ssh/ssh_host_ed25519_key /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys and are used for host-based authentication. /etc/ssh/ssh_known_hosts Systemwide list of known host keys. This file should be prepared by the system administrator to contain the public host keys of all machines in the organization. It should be world-readable. See sshd(8) for further details of the format of this file. /etc/ssh/sshrc Commands in this file are executed by when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information. EXIT STATUS top exits with the exit status of the remote command or with 255 if an error occurred. SEE ALSO top scp(1), sftp(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), ssh-keyscan(1), tun(4), ssh_config(5), ssh-keysign(8), sshd(8) STANDARDS top S. Lehtinen and C. Lonvick, The Secure Shell (SSH) Protocol Assigned Numbers, RFC 4250, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Protocol Architecture, RFC 4251, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Authentication Protocol, RFC 4252, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Transport Layer Protocol, RFC 4253, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Connection Protocol, RFC 4254, January 2006. J. Schlyter and W. Griffin, Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints, RFC 4255, January 2006. F. Cusack and M. Forssen, Generic Message Exchange Authentication for the Secure Shell Protocol (SSH), RFC 4256, January 2006. J. Galbraith and P. Remaker, The Secure Shell (SSH) Session Channel Break Extension, RFC 4335, January 2006. M. Bellare, T. Kohno, and C. Namprempre, The Secure Shell (SSH) Transport Layer Encryption Modes, RFC 4344, January 2006. B. Harris, Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol, RFC 4345, January 2006. M. Friedl, N. Provos, and W. Simpson, Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol, RFC 4419, March 2006. J. Galbraith and R. Thayer, The Secure Shell (SSH) Public Key File Format, RFC 4716, November 2006. D. Stebila and J. Green, Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer, RFC 5656, December 2009. A. Perrig and D. Song, Hash Visualization: a New Technique to improve Real-World Security, 1999, International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99). AUTHORS top OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re- added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. COLOPHON top This page is part of the openssh (Portable OpenSSH) project. Information about the project can be found at http://www.openssh.com/portable.html. If you have a bug report for this manual page, see http://www.openssh.com/report.html. This page was obtained from the tarball openssh-9.6p1.tar.gz fetched from http://ftp.eu.openbsd.org/pub/OpenBSD/OpenSSH/portable/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU October 11, 2023 SSH(1) Pages that refer to this page: stap-jupyter(1), systemd-stdio-bridge(1), tar(1), sd_bus_default(3), environment.d(5), proc(5), user@.service(5), pty(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Changes to the directory where 'ssh' executable is located. Bash Command:<START>cd $(dirname $(which ssh));<END>

Check all .txt files whether they contain "needle"

find . -type f -iname "*.txt" -print | xargs grep "needle"

['find', 'xargs', 'grep']

Output a Bash command to accomplish the following task. Task: Check all .txt files whether they contain "needle" Bash Command:<START>find . -type f -iname "*.txt" -print | xargs grep "needle"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n Task: Check all .txt files whether they contain "needle" Bash Command:<START>find . -type f -iname "*.txt" -print | xargs grep "needle"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check all .txt files whether they contain "needle" Bash Command:<START>find . -type f -iname "*.txt" -print | xargs grep "needle"<END>

Check all .txt files whose names may contain spaces whether they contain "needle"

find . -type f -iname "*.txt" -print0 | xargs -0 grep "needle"

['find', 'xargs', 'grep']

Output a Bash command to accomplish the following task. Task: Check all .txt files whose names may contain spaces whether they contain "needle" Bash Command:<START>find . -type f -iname "*.txt" -print0 | xargs -0 grep "needle"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n Task: Check all .txt files whose names may contain spaces whether they contain "needle" Bash Command:<START>find . -type f -iname "*.txt" -print0 | xargs -0 grep "needle"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check all .txt files whose names may contain spaces whether they contain "needle" Bash Command:<START>find . -type f -iname "*.txt" -print0 | xargs -0 grep "needle"<END>

Check if "$file" contains DOS line endings

od -t x2 -N 1000 $file | cut -c8- | egrep -m1 -q ' 0d| 0d|0d$'

['cut', 'od']

Output a Bash command to accomplish the following task. Task: Check if "$file" contains DOS line endings Bash Command:<START>od -t x2 -N 1000 $file | cut -c8- | egrep -m1 -q ' 0d| 0d|0d$'<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # cut\n\n> Cut out fields from `stdin` or files.\n> More information: <https://www.gnu.org/software/coreutils/cut>.\n\n- Print a specific character/field range of each line:\n\n`{{command}} | cut --{{characters|fields}}={{1|1,10|1-10|1-|-10}}`\n\n- Print a field range of each line with a specific delimiter:\n\n`{{command}} | cut --delimiter="{{,}}" --fields={{1}}`\n\n- Print a character range of each line of the specific file:\n\n`cut --characters={{1}} {{path/to/file}}`\n # od\n\n> Display file contents in octal, decimal or hexadecimal format.\n> Optionally display the byte offsets and/or printable representation for each line.\n> More information: <https://www.gnu.org/software/coreutils/od>.\n\n- Display file using default settings: octal format, 8 bytes per line, byte offsets in octal, and duplicate lines replaced with `*`:\n\n`od {{path/to/file}}`\n\n- Display file in verbose mode, i.e. without replacing duplicate lines with `*`:\n\n`od -v {{path/to/file}}`\n\n- Display file in hexadecimal format (2-byte units), with byte offsets in decimal format:\n\n`od --format={{x}} --address-radix={{d}} -v {{path/to/file}}`\n\n- Display file in hexadecimal format (1-byte units), and 4 bytes per line:\n\n`od --format={{x1}} --width={{4}} -v {{path/to/file}}`\n\n- Display file in hexadecimal format along with its character representation, and do not print byte offsets:\n\n`od --format={{xz}} --address-radix={{n}} -v {{path/to/file}}`\n\n- Read only 100 bytes of a file starting from the 500th byte:\n\n`od --read-bytes {{100}} --skip-bytes={{500}} -v {{path/to/file}}`\n Task: Check if "$file" contains DOS line endings Bash Command:<START>od -t x2 -N 1000 $file | cut -c8- | egrep -m1 -q ' 0d| 0d|0d$'<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: cut(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cut(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CUT(1) User Commands CUT(1) NAME top cut - remove sections from each line of files SYNOPSIS top cut OPTION... [FILE]... DESCRIPTION top Print selected parts of lines from each FILE to standard output. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. -b, --bytes=LIST select only these bytes -c, --characters=LIST select only these characters -d, --delimiter=DELIM use DELIM instead of TAB for field delimiter -f, --fields=LIST select only these fields; also print any line that contains no delimiter character, unless the -s option is specified -n (ignored) --complement complement the set of selected bytes, characters or fields -s, --only-delimited do not print lines not containing delimiters --output-delimiter=STRING use STRING as the output delimiter the default is to use the input delimiter -z, --zero-terminated line delimiter is NUL, not newline --help display this help and exit --version output version information and exit Use one, and only one of -b, -c or -f. Each LIST is made up of one range, or many ranges separated by commas. Selected input is written in the same order that it is read, and is written exactly once. Each range is one of: N N'th byte, character or field, counted from 1 N- from N'th byte, character or field, to end of line N-M from N'th to M'th (included) byte, character or field -M from first to M'th (included) byte, character or field AUTHOR top Written by David M. Ihnat, David MacKenzie, and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top Full documentation <https://www.gnu.org/software/coreutils/cut> or available locally via: info '(coreutils) cut invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CUT(1) Pages that refer to this page: man-pages(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. od(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training od(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON OD(1) User Commands OD(1) NAME top od - dump files in octal and other formats SYNOPSIS top od [OPTION]... [FILE]... od [-abcdfilosx]... [FILE] [[+]OFFSET[.][b]] od --traditional [OPTION]... [FILE] [[+]OFFSET[.][b] [+][LABEL][.][b]] DESCRIPTION top Write an unambiguous representation, octal bytes by default, of FILE to standard output. With more than one FILE argument, concatenate them in the listed order to form the input. With no FILE, or when FILE is -, read standard input. If first and second call formats both apply, the second format is assumed if the last operand begins with + or (if there are 2 operands) a digit. An OFFSET operand means -j OFFSET. LABEL is the pseudo-address at first byte printed, incremented when dump is progressing. For OFFSET and LABEL, a 0x or 0X prefix indicates hexadecimal; suffixes may be . for octal and b for multiply by 512. Mandatory arguments to long options are mandatory for short options too. -A, --address-radix=RADIX output format for file offsets; RADIX is one of [doxn], for Decimal, Octal, Hex or None --endian={big|little} swap input bytes according the specified order -j, --skip-bytes=BYTES skip BYTES input bytes first -N, --read-bytes=BYTES limit dump to BYTES input bytes -S BYTES, --strings[=BYTES] show only NUL terminated strings of at least BYTES (3) printable characters -t, --format=TYPE select output format or formats -v, --output-duplicates do not use * to mark line suppression -w[BYTES], --width[=BYTES] output BYTES bytes per output line; 32 is implied when BYTES is not specified --traditional accept arguments in third form above --help display this help and exit --version output version information and exit Traditional format specifications may be intermixed; they accumulate: -a same as -t a, select named characters, ignoring high-order bit -b same as -t o1, select octal bytes -c same as -t c, select printable characters or backslash escapes -d same as -t u2, select unsigned decimal 2-byte units -f same as -t fF, select floats -i same as -t dI, select decimal ints -l same as -t dL, select decimal longs -o same as -t o2, select octal 2-byte units -s same as -t d2, select decimal 2-byte units -x same as -t x2, select hexadecimal 2-byte units TYPE is made up of one or more of these specifications: a named character, ignoring high-order bit c printable character or backslash escape d[SIZE] signed decimal, SIZE bytes per integer f[SIZE] floating point, SIZE bytes per float o[SIZE] octal, SIZE bytes per integer u[SIZE] unsigned decimal, SIZE bytes per integer x[SIZE] hexadecimal, SIZE bytes per integer SIZE is a number. For TYPE in [doux], SIZE may also be C for sizeof(char), S for sizeof(short), I for sizeof(int) or L for sizeof(long). If TYPE is f, SIZE may also be F for sizeof(float), D for sizeof(double) or L for sizeof(long double). Adding a z suffix to any type displays printable characters at the end of each output line. BYTES is hex with 0x or 0X prefix, and may have a multiplier suffix: b 512 KB 1000 K 1024 MB 1000*1000 M 1024*1024 and so on for G, T, P, E, Z, Y, R, Q. Binary prefixes can be used, too: KiB=K, MiB=M, and so on. EXAMPLES top od -A x -t x1z -v Display hexdump format output od -A o -t oS -w16 The default output format used by od AUTHOR top Written by Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top Full documentation <https://www.gnu.org/software/coreutils/od> or available locally via: info '(coreutils) od invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 OD(1) Pages that refer to this page: scr_dump(5) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if "$file" contains DOS line endings Bash Command:<START>od -t x2 -N 1000 $file | cut -c8- | egrep -m1 -q ' 0d| 0d|0d$'<END>

Check if "/path/to/dir" is a nfs mount point

mount -l | grep 'type nfs' | sed 's/.* on \([^ ]*\) .*/\1/' | grep /path/to/dir

['sed', 'mount', 'grep']

Output a Bash command to accomplish the following task. Task: Check if "/path/to/dir" is a nfs mount point Bash Command:<START>mount -l | grep 'type nfs' | sed 's/.* on \([^ ]*\) .*/\1/' | grep /path/to/dir<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # sed\n\n> Edit text in a scriptable manner.\n> See also: `awk`, `ed`.\n> More information: <https://www.gnu.org/software/sed/manual/sed.html>.\n\n- Replace all `apple` (basic regex) occurrences with `mango` (basic regex) in all input lines and print the result to `stdout`:\n\n`{{command}} | sed 's/apple/mango/g'`\n\n- Replace all `apple` (extended regex) occurrences with `APPLE` (extended regex) in all input lines and print the result to `stdout`:\n\n`{{command}} | sed -E 's/(apple)/\U\1/g'`\n\n- Replace all `apple` (basic regex) occurrences with `mango` (basic regex) in a specific file and overwrite the original file in place:\n\n`sed -i 's/apple/mango/g' {{path/to/file}}`\n\n- Execute a specific script [f]ile and print the result to `stdout`:\n\n`{{command}} | sed -f {{path/to/script.sed}}`\n\n- Print just the first line to `stdout`:\n\n`{{command}} | sed -n '1p'`\n\n- [d]elete the first line of a file:\n\n`sed -i 1d {{path/to/file}}`\n\n- [i]nsert a new line at the first line of a file:\n\n`sed -i '1i\your new line text\' {{path/to/file}}`\n # mount\n\n> Provides access to an entire filesystem in one directory.\n> More information: <https://manned.org/mount.8>.\n\n- Show all mounted filesystems:\n\n`mount`\n\n- Mount a device to a directory:\n\n`mount -t {{filesystem_type}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Create a specific directory if it does not exist and mount a device to it:\n\n`mount --mkdir {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a device to a directory for a specific user:\n\n`mount -o uid={{user_id}},gid={{group_id}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a CD-ROM device (with the filetype ISO9660) to `/cdrom` (readonly):\n\n`mount -t {{iso9660}} -o ro {{/dev/cdrom}} {{/cdrom}}`\n\n- Mount all the filesystem defined in `/etc/fstab`:\n\n`mount -a`\n\n- Mount a specific filesystem described in `/etc/fstab` (e.g. `/dev/sda1 /my_drive ext2 defaults 0 2`):\n\n`mount {{/my_drive}}`\n\n- Mount a directory to another directory:\n\n`mount --bind {{path/to/old_dir}} {{path/to/new_dir}}`\n # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n Task: Check if "/path/to/dir" is a nfs mount point Bash Command:<START>mount -l | grep 'type nfs' | sed 's/.* on \([^ ]*\) .*/\1/' | grep /path/to/dir<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: sed(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sed(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND SYNOPSIS | REGULAR EXPRESSIONS | BUGS | AUTHOR | COPYRIGHT | SEE ALSO | COLOPHON SED(1) User Commands SED(1) NAME top sed - stream editor for filtering and transforming text SYNOPSIS top sed [-V] [--version] [--help] [-n] [--quiet] [--silent] [-l N] [--line-length=N] [-u] [--unbuffered] [-E] [-r] [--regexp-extended] [-e script] [--expression=script] [-f script-file] [--file=script-file] [script-if-no-other-script] [file...] DESCRIPTION top Sed is a stream editor. A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline). While in some ways similar to an editor which permits scripted edits (such as ed), sed works by making only one pass over the input(s), and is consequently more efficient. But it is sed's ability to filter text in a pipeline which particularly distinguishes it from other types of editors. -n, --quiet, --silent suppress automatic printing of pattern space --debug annotate program execution -e script, --expression=script add the script to the commands to be executed -f script-file, --file=script-file add the contents of script-file to the commands to be executed --follow-symlinks follow symlinks when processing in place -i[SUFFIX], --in-place[=SUFFIX] edit files in place (makes backup if SUFFIX supplied) -l N, --line-length=N specify the desired line-wrap length for the `l' command --posix disable all GNU extensions. -E, -r, --regexp-extended use extended regular expressions in the script (for portability use POSIX -E). -s, --separate consider files as separate rather than as a single, continuous long stream. --sandbox operate in sandbox mode (disable e/r/w commands). -u, --unbuffered load minimal amounts of data from the input files and flush the output buffers more often -z, --null-data separate lines by NUL characters --help display this help and exit --version output version information and exit If no -e, --expression, -f, or --file option is given, then the first non-option argument is taken as the sed script to interpret. All remaining arguments are names of input files; if no input files are specified, then the standard input is read. GNU sed home page: <https://www.gnu.org/software/sed/>. General help using GNU software: <https://www.gnu.org/gethelp/>. E-mail bug reports to: <bug-sed@gnu.org>. COMMAND SYNOPSIS top This is just a brief synopsis of sed commands to serve as a reminder to those who already know sed; other documentation (such as the texinfo document) must be consulted for fuller descriptions. Zero-address ``commands'' : label Label for b and t commands. #comment The comment extends until the next newline (or the end of a -e script fragment). } The closing bracket of a { } block. Zero- or One- address commands = Print the current line number. a \ text Append text, which has each embedded newline preceded by a backslash. i \ text Insert text, which has each embedded newline preceded by a backslash. q [exit-code] Immediately quit the sed script without processing any more input, except that if auto-print is not disabled the current pattern space will be printed. The exit code argument is a GNU extension. Q [exit-code] Immediately quit the sed script without processing any more input. This is a GNU extension. r filename Append text read from filename. R filename Append a line read from filename. Each invocation of the command reads a line from the file. This is a GNU extension. Commands which accept address ranges { Begin a block of commands (end with a }). b label Branch to label; if label is omitted, branch to end of script. c \ text Replace the selected lines with text, which has each embedded newline preceded by a backslash. d Delete pattern space. Start next cycle. D If pattern space contains no newline, start a normal new cycle as if the d command was issued. Otherwise, delete text in the pattern space up to the first newline, and restart cycle with the resultant pattern space, without reading a new line of input. h H Copy/append pattern space to hold space. g G Copy/append hold space to pattern space. l List out the current line in a ``visually unambiguous'' form. l width List out the current line in a ``visually unambiguous'' form, breaking it at width characters. This is a GNU extension. n N Read/append the next line of input into the pattern space. p Print the current pattern space. P Print up to the first embedded newline of the current pattern space. s/regexp/replacement/ Attempt to match regexp against the pattern space. If successful, replace that portion matched with replacement. The replacement may contain the special character & to refer to that portion of the pattern space which matched, and the special escapes \1 through \9 to refer to the corresponding matching sub-expressions in the regexp. t label If a s/// has done a successful substitution since the last input line was read and since the last t or T command, then branch to label; if label is omitted, branch to end of script. T label If no s/// has done a successful substitution since the last input line was read and since the last t or T command, then branch to label; if label is omitted, branch to end of script. This is a GNU extension. w filename Write the current pattern space to filename. W filename Write the first line of the current pattern space to filename. This is a GNU extension. x Exchange the contents of the hold and pattern spaces. y/source/dest/ Transliterate the characters in the pattern space which appear in source to the corresponding character in dest. Addresses Sed commands can be given with no addresses, in which case the command will be executed for all input lines; with one address, in which case the command will only be executed for input lines which match that address; or with two addresses, in which case the command will be executed for all input lines which match the inclusive range of lines starting from the first address and continuing to the second address. Three things to note about address ranges: the syntax is addr1,addr2 (i.e., the addresses are separated by a comma); the line which addr1 matched will always be accepted, even if addr2 selects an earlier line; and if addr2 is a regexp, it will not be tested against the line that addr1 matched. After the address (or address-range), and before the command, a ! may be inserted, which specifies that the command shall only be executed if the address (or address-range) does not match. The following address types are supported: number Match only the specified line number (which increments cumulatively across files, unless the -s option is specified on the command line). first~step Match every step'th line starting with line first. For example, ``sed -n 1~2p'' will print all the odd-numbered lines in the input stream, and the address 2~5 will match every fifth line, starting with the second. first can be zero; in this case, sed operates as if it were equal to step. (This is an extension.) $ Match the last line. /regexp/ Match lines matching the regular expression regexp. Matching is performed on the current pattern space, which can be modified with commands such as ``s///''. \cregexpc Match lines matching the regular expression regexp. The c may be any character. GNU sed also supports some special 2-address forms: 0,addr2 Start out in "matched first address" state, until addr2 is found. This is similar to 1,addr2, except that if addr2 matches the very first line of input the 0,addr2 form will be at the end of its range, whereas the 1,addr2 form will still be at the beginning of its range. This works only when addr2 is a regular expression. addr1,+N Will match addr1 and the N lines following addr1. addr1,~N Will match addr1 and the lines following addr1 until the next line whose input line number is a multiple of N. REGULAR EXPRESSIONS top POSIX.2 BREs should be supported, but they aren't completely because of performance problems. The \n sequence in a regular expression matches the newline character, and similarly for \a, \t, and other sequences. The -E option switches to using extended regular expressions instead; it has been supported for years by GNU sed, and is now included in POSIX. BUGS top E-mail bug reports to bug-sed@gnu.org. Also, please include the output of ``sed --version'' in the body of your report if at all possible. AUTHOR top Written by Jay Fenlason, Tom Lord, Ken Pizzini, Paolo Bonzini, Jim Meyering, and Assaf Gordon. This sed program was built with SELinux support. SELinux is enabled on this system. GNU sed home page: <https://www.gnu.org/software/sed/>. General help using GNU software: <https://www.gnu.org/gethelp/>. E-mail bug reports to: <bug-sed@gnu.org>. COPYRIGHT top Copyright 2022 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top awk(1), ed(1), grep(1), tr(1), perlre(1), sed.info, any of various books on sed, the sed FAQ (http://sed.sf.net/grabbag/tutorials/sedfaq.txt), http://sed.sf.net/grabbag/. The full documentation for sed is maintained as a Texinfo manual. If the info and sed programs are properly installed at your site, the command info sed should give you access to the complete manual. COLOPHON top This page is part of the sed (stream-oriented editor) project. Information about the project can be found at http://www.gnu.org/software/sed/. If you have a bug report for this manual page, send it to bug-sed@gnu.org. This page was obtained from the tarball sed-4.9.tar.gz fetched from https://www.gnu.org/software/sed/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU sed 4.9 November 2022 SED(1) Pages that refer to this page: gawk(1), grep(1), iostat2pcp(1), pmdaopenmetrics(1), pmlogrewrite(1), sheet2pcp(1), cpuset(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. mount(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training mount(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND-LINE OPTIONS | FILESYSTEM-INDEPENDENT MOUNT OPTIONS | FILESYSTEM-SPECIFIC MOUNT OPTIONS | DM-VERITY SUPPORT | LOOP-DEVICE SUPPORT | EXIT STATUS | EXTERNAL HELPERS | ENVIRONMENT | FILES | HISTORY | BUGS | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY MOUNT(8) System Administration MOUNT(8) NAME top mount - mount a filesystem SYNOPSIS top mount [-h|-V] mount [-l] [-t fstype] mount -a [-fFnrsvw] [-t fstype] [-O optlist] mount [-fnrsvw] [-o options] device|mountpoint mount [-fnrsvw] [-t fstype] [-o options] device mountpoint mount --bind|--rbind|--move olddir newdir mount --make-[shared|slave|private|unbindable|rshared|rslave|rprivate|runbindable] mountpoint DESCRIPTION top All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the filesystem found on some device to the big file tree. Conversely, the umount(8) command will detach it again. The filesystem is used to control how data is stored on the device or provided in a virtual way by network or other services. The standard form of the mount command is: mount -t type device dir This tells the kernel to attach the filesystem found on device (which is of type type) at the directory dir. The option -t type is optional. The mount command is usually able to detect a filesystem. The root permissions are necessary to mount a filesystem by default. See section "Non-superuser mounts" below for more details. The previous contents (if any) and owner and mode of dir become invisible, and as long as this filesystem remains mounted, the pathname dir refers to the root of the filesystem on device. If only the directory or the device is given, for example: mount /dir then mount looks for a mountpoint (and if not found then for a device) in the /etc/fstab file. Its possible to use the --target or --source options to avoid ambiguous interpretation of the given argument. For example: mount --target /mountpoint The same filesystem may be mounted more than once, and in some cases (e.g., network filesystems) the same filesystem may be mounted on the same mountpoint multiple times. The mount command does not implement any policy to control this behavior. All behavior is controlled by the kernel and it is usually specific to the filesystem driver. The exception is --all, in this case already mounted filesystems are ignored (see --all below for more details). Listing the mounts The listing mode is maintained for backward compatibility only. For more robust and customizable output use findmnt(8), especially in your scripts. Note that control characters in the mountpoint name are replaced with '?'. The following command lists all mounted filesystems (of type type): mount [-l] [-t type] The option -l adds labels to this listing. See below. Indicating the device and filesystem Most devices are indicated by a filename (of a block special device), like /dev/sda1, but there are other possibilities. For example, in the case of an NFS mount, device may look like knuth.cwi.nl:/dir. The device names of disk partitions are unstable; hardware reconfiguration, and adding or removing a device can cause changes in names. This is the reason why its strongly recommended to use filesystem or partition identifiers like UUID or LABEL. Currently supported identifiers (tags): LABEL=label Human readable filesystem identifier. See also -L. UUID=uuid Filesystem universally unique identifier. The format of the UUID is usually a series of hex digits separated by hyphens. See also -U. Note that mount uses UUIDs as strings. The UUIDs from the command line or from fstab(5) are not converted to internal binary representation. The string representation of the UUID should be based on lower case characters. PARTLABEL=label Human readable partition identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). PARTUUID=uuid Partition universally unique identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). ID=id Hardware block device ID as generated by udevd. This identifier is usually based on WWN (unique storage identifier) and assigned by the hardware manufacturer. See ls /dev/disk/by-id for more details, this directory and running udevd is required. This identifier is not recommended for generic use as the identifier is not strictly defined and it depends on udev, udev rules and hardware. The command lsblk --fs provides an overview of filesystems, LABELs and UUIDs on available block devices. The command blkid -p <device> provides details about a filesystem on the specified device. Dont forget that there is no guarantee that UUIDs and labels are really unique, especially if you move, share or copy the device. Use lsblk -o +UUID,PARTUUID to verify that the UUIDs are really unique in your system. The recommended setup is to use tags (e.g. UUID=uuid) rather than /dev/disk/by-{label,uuid,id,partuuid,partlabel} udev symlinks in the /etc/fstab file. Tags are more readable, robust and portable. The mount(8) command internally uses udev symlinks, so the use of symlinks in /etc/fstab has no advantage over tags. For more details see libblkid(3). The proc filesystem is not associated with a special device, and when mounting it, an arbitrary keyword - for example, proc - can be used instead of a device specification. (The customary choice none is less fortunate: the error message 'none already mounted' from mount can be confusing.) The files /etc/fstab, /etc/mtab and /proc/mounts The file /etc/fstab (see fstab(5)), may contain lines describing what devices are usually mounted where, using which options. The default location of the fstab(5) file can be overridden with the --fstab path command-line option (see below for more details). The command mount -a [-t type] [-O optlist] (usually given in a bootscript) causes all filesystems mentioned in fstab (of the proper type and/or having or not having the proper options) to be mounted as indicated, except for those whose line contains the noauto keyword. Adding the -F option will make mount fork, so that the filesystems are mounted in parallel. When mounting a filesystem mentioned in fstab or mtab, it suffices to specify on the command line only the device, or only the mount point. The programs mount and umount(8) traditionally maintained a list of currently mounted filesystems in the file /etc/mtab. The support for regular classic /etc/mtab is completely disabled at compile time by default, because on current Linux systems it is better to make /etc/mtab a symlink to /proc/mounts instead. The regular mtab file maintained in userspace cannot reliably work with namespaces, containers and other advanced Linux features. If the regular mtab support is enabled, then its possible to use the file as well as the symlink. If no arguments are given to mount, the list of mounted filesystems is printed. If you want to override mount options from /etc/fstab, you have to use the -o option: mount device|dir -o options and then the mount options from the command line will be appended to the list of options from /etc/fstab. This default behaviour can be changed using the --options-mode command-line option. The usual behavior is that the last option wins if there are conflicting ones. The mount program does not read the /etc/fstab file if both device (or LABEL, UUID, ID, PARTUUID or PARTLABEL) and dir are specified. For example, to mount device foo at /dir: mount /dev/foo /dir This default behaviour can be changed by using the --options-source-force command-line option to always read configuration from fstab. For non-root users mount always reads the fstab configuration. Non-superuser mounts Normally, only the superuser can mount filesystems. However, when fstab contains the user option on a line, anybody can mount the corresponding filesystem. Thus, given a line /dev/cdrom /cd iso9660 ro,user,noauto,unhide any user can mount the iso9660 filesystem found on an inserted CDROM using the command: mount /cd Note that mount is very strict about non-root users and all paths specified on command line are verified before fstab is parsed or a helper program is executed. Its strongly recommended to use a valid mountpoint to specify filesystem, otherwise mount may fail. For example its a bad idea to use NFS or CIFS source on command line. Since util-linux 2.35, mount does not exit when user permissions are inadequate according to libmounts internal security rules. Instead, it drops suid permissions and continues as regular non-root user. This behavior supports use-cases where root permissions are not necessary (e.g., fuse filesystems, user namespaces, etc). For more details, see fstab(5). Only the user that mounted a filesystem can unmount it again. If any user should be able to unmount it, then use users instead of user in the fstab line. The owner option is similar to the user option, with the restriction that the user must be the owner of the special file. This may be useful e.g. for /dev/fd if a login script makes the console user owner of this device. The group option is similar, with the restriction that the user must be a member of the group of the special file. The user mount option is accepted if no username is specified. If used in the format user=someone, the option is silently ignored and visible only for external mount helpers (/sbin/mount.<type>) for compatibility with some network filesystems. Bind mount operation Remount part of the file hierarchy somewhere else. The call is: mount --bind olddir newdir or by using this fstab entry: /olddir /newdir none bind After this call the same contents are accessible in two places. It is important to understand that "bind" does not create any second-class or special node in the kernel VFS. The "bind" is just another operation to attach a filesystem. There is nowhere stored information that the filesystem has been attached by a "bind" operation. The olddir and newdir are independent and the olddir may be unmounted. One can also remount a single file (on a single file). Its also possible to use a bind mount to create a mountpoint from a regular directory, for example: mount --bind foo foo The bind mount call attaches only (part of) a single filesystem, not possible submounts. The entire file hierarchy including submounts can be attached a second place by using: mount --rbind olddir newdir Note that the filesystem mount options maintained by the kernel will remain the same as those on the original mount point. The userspace mount options (e.g., _netdev) will not be copied by mount and its necessary to explicitly specify the options on the mount command line. Since util-linux 2.27 mount permits changing the mount options by passing the relevant options along with --bind. For example: mount -o bind,ro foo foo This feature is not supported by the Linux kernel; it is implemented in userspace by an additional mount(2) remounting system call. This solution is not atomic. The alternative (classic) way to create a read-only bind mount is to use the remount operation, for example: mount --bind olddir newdir mount -o remount,bind,ro olddir newdir Note that a read-only bind will create a read-only mountpoint (VFS entry), but the original filesystem superblock will still be writable, meaning that the olddir will be writable, but the newdir will be read-only. Its also possible to change nosuid, nodev, noexec, noatime, nodiratime, relatime and nosymfollow VFS entry flags via a "remount,bind" operation. The other flags (for example filesystem-specific flags) are silently ignored. The classic mount(2) system call does not allow to change mount options recursively (for example with -o rbind,ro). The recursive semantic is possible with a new mount_setattr(2) kernel system call and its supported since libmount from util-linux v2.39 by a new experimental "recursive" option argument (e.g. -o rbind,ro=recursive). For more details see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS section. Since util-linux 2.31, mount ignores the bind flag from /etc/fstab on a remount operation (if -o remount is specified on command line). This is necessary to fully control mount options on remount by command line. In previous versions the bind flag has been always applied and it was impossible to re-define mount options without interaction with the bind semantic. This mount behavior does not affect situations when "remount,bind" is specified in the /etc/fstab file. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink. This feature is usable (only) with the new kernel mount API where bind mount over symlinks is supported. The move operation Move a mounted tree to another place (atomically). The call is: mount --move olddir newdir This will cause the contents which previously appeared under olddir to now be accessible under newdir. The physical location of the files is not changed. Note that olddir has to be a mountpoint. Note also that moving a mount residing under a shared mount is invalid and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current propagation flags. Shared subtree operations Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, private, slave or unbindable. A shared mount provides the ability to create mirrors of that mount such that mounts and unmounts within any of the mirrors propagate to the other mirror. A slave mount receives propagation from its master, but not vice versa. A private mount carries no propagation abilities. An unbindable mount is a private mount which cannot be cloned through a bind operation. The detailed semantics are documented in Documentation/filesystems/sharedsubtree.txt file in the kernel source tree; see also mount_namespaces(7). Supported operations are: mount --make-shared mountpoint mount --make-slave mountpoint mount --make-private mountpoint mount --make-unbindable mountpoint The following commands allow one to recursively change the type of all the mounts under a given mountpoint. mount --make-rshared mountpoint mount --make-rslave mountpoint mount --make-rprivate mountpoint mount --make-runbindable mountpoint mount does not read fstab(5) when a --make-* operation is requested. All necessary information has to be specified on the command line. Note that the Linux kernel does not allow changing multiple propagation flags with a single mount(2) system call, and the flags cannot be mixed with other mount options and operations. Since util-linux 2.23 the mount command can be used to do more propagation (topology) changes by one mount(8) call and do it also together with other mount operations. The propagation flags are applied by additional mount(2) system calls when the preceding mount operations were successful. Note that this use case is not atomic. It is possible to specify the propagation flags in fstab(5) as mount options (private, slave, shared, unbindable, rprivate, rslave, rshared, runbindable). For example: mount --make-private --make-unbindable /dev/sda1 /foo is the same as: mount /dev/sda1 /foo mount --make-private /foo mount --make-unbindable /foo COMMAND-LINE OPTIONS top The full set of mount options used by an invocation of mount is determined by first extracting the mount options for the filesystem from the fstab table, then applying any options specified by the -o argument, and finally applying a -r or -w option, when present. The mount command does not pass all command-line options to the /sbin/mount.suffix mount helpers. The interface between mount and the mount helpers is described below in the EXTERNAL HELPERS section. Command-line options available for the mount command are: -a, --all Mount all filesystems (of the given types) mentioned in fstab (except for those whose line contains the noauto keyword). The filesystems are mounted following their order in fstab. The mount command compares filesystem source, target (and fs root for bind mount or btrfs) to detect already mounted filesystems. The kernel table with already mounted filesystems is cached during mount --all. This means that all duplicated fstab entries will be mounted. The correct functionality depends on /proc (to detect already mounted filesystems) and on /sys (to evaluate filesystem tags like UUID= or LABEL=). Its strongly recommended to mount /proc and /sys filesystems before mount -a is executed, or keep /proc and /sys at the beginning of fstab. The option --all is possible to use for remount operation too. In this case all filters (-t and -O) are applied to the table of already mounted filesystems. Since version 2.35 it is possible to use the command line option -o to alter mount options from fstab (see also --options-mode). Note that it is a bad practice to use mount -a for fstab checking. The recommended solution is findmnt --verify. -B, --bind Remount a subtree somewhere else (so that its contents are available in both places). See above, under Bind mount operation. -c, --no-canonicalize Dont canonicalize paths. The mount command canonicalizes all paths (from the command line or fstab) by default. The option is designed for mount helpers which call mount -i. It is strongly recommended to not use this command-line option for normal mount operations. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink (see "Bind mount operation" section for more details). Note that mount does not pass this option to the /sbin/mount.type helpers. -F, --fork (Used in conjunction with -a.) Fork off a new incarnation of mount for each device. This will do the mounts on different devices or different NFS servers in parallel. This has the advantage that it is faster; also NFS timeouts proceed in parallel. A disadvantage is that the order of the mount operations is undefined. Thus, you cannot use this option if you want to mount both /usr and /usr/spool. -f, --fake Causes everything to be done except for the mount-related system calls. The --fake option was originally designed to write an entry to /etc/mtab without actually mounting. The /etc/mtab is no longer maintained in userspace, and starting from version 2.39, the mount operation can be a complex chain of operations with dependencies between the syscalls. The --fake option forces libmount to skip all mount source preparation, mount option analysis, and the actual mounting process. The difference between fake and non-fake execution is huge. This is the reason why the --fake option has minimal significance for the current mount(8) implementation and it is maintained mostly for backward compatibility. -i, --internal-only Dont call the /sbin/mount.filesystem helper even if it exists. -L, --label label Mount the partition that has the specified label. -l, --show-labels Add the labels in the mount output. mount must have permission to read the disk device (e.g. be set-user-ID root) for this to work. One can set such a label for ext2, ext3 or ext4 using the e2label(8) utility, or for XFS using xfs_admin(8), or for reiserfs using reiserfstune(8). -M, --move Move a subtree to some other place. See above, the subsection The move operation. -m, --mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. Alias to "-o X-mount.mkdir[=mode]", the default mode is 0755. For more details see X-mount.mkdir below. --map-groups, --map-users inner:_outer_:_count_ Add the specified user/group mapping to an X-mount.idmap map. These options can be given multiple times to build up complete mappings for users and groups. For more details see X-mount.idmap below. --map-users /proc/PID/ns/user Use the specified user namespace for user and group mapping in an id-mapped mount. This is an alias for "-o X-mount.idmap=/proc/PID/ns/user" and cannot be used twice nor together with the inner:_outer_:_count_ option format above. For more details see X-mount.idmap below. -n, --no-mtab Mount without writing in /etc/mtab. This is necessary for example when /etc is on a read-only filesystem. -N, --namespace ns Perform the mount operation in the mount namespace specified by ns. ns is either PID of process running in that namespace or special file representing that namespace. mount switches to the mount namespace when it reads /etc/fstab, writes /etc/mtab: (or writes to _/run/mount) and calls mount(2), otherwise it runs in the original mount namespace. This means that the target namespace does not have to contain any libraries or other requirements necessary to execute the mount(2) call. See mount_namespaces(7) for more information. -O, --test-opts opts Limit the set of filesystems to which the -a option applies. In this regard it is like the -t option except that -O is useless without -a. For example, the command mount -a -O no_netdev mounts all filesystems except those which have the option netdev specified in the options field in the /etc/fstab file. It is different from -t in that each option is matched exactly; a leading no at the beginning of one option does not negate the rest. The -t and -O options are cumulative in effect; that is, the command mount -a -t ext2 -O _netdev mounts all ext2 filesystems with the _netdev option, not all filesystems that are either ext2 or have the _netdev option specified. -o, --options opts Use the specified mount options. The opts argument is a comma-separated list. For example: mount LABEL=mydisk -o noatime,nodev,nosuid Note that the order of the options matters, as the last option wins if there are conflicting ones. The options from the command line also overwrite options from fstab by default. For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections. --onlyonce Forces mount command to check if the filesystem is already mounted. This behavior is the default for --all; otherwise, it depends on the kernel filesystem driver. Some filesystems may be mounted more than once on the same mount point (e.g. tmpfs). --options-mode mode Controls how to combine options from fstab/mtab with options from the command line. mode can be one of ignore, append, prepend or replace. For example, append means that options from fstab are appended to options from the command line. The default value is prepend it means command line options are evaluated after fstab options. Note that the last option wins if there are conflicting ones. --options-source source Source of default options. source is a comma-separated list of fstab, mtab and disable. disable disables fstab and mtab and enables --options-source-force. The default value is fstab,mtab. --options-source-force Use options from fstab/mtab even if both device and dir are specified. -R, --rbind Remount a subtree and all possible submounts somewhere else (so that its contents are available in both places). See above, the subsection Bind mount operation. -r, --read-only Mount the filesystem read-only. A synonym is -o ro. Note that, depending on the filesystem type, state and kernel behavior, the system may still write to the device. For example, ext3 and ext4 will replay the journal if the filesystem is dirty. To prevent this kind of write access, you may want to mount an ext3 or ext4 filesystem with the ro,noload mount options or set the block device itself to read-only mode, see the blockdev(8) command. -s Tolerate sloppy mount options rather than failing. This will ignore mount options not supported by a filesystem type. Not all filesystems support this option. Currently its supported by the mount.nfs mount helper only. --source device If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount source. --target directory If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount target. --target-prefix directory Prepend the specified directory to all mount targets. This option can be used to follow fstab, but mount operations are done in another place, for example: mount --all --target-prefix /chroot -o X-mount.mkdir mounts all from system fstab to /chroot, all missing mountpoint are created (due to X-mount.mkdir). See also --fstab to use an alternative fstab. -T, --fstab path Specifies an alternative fstab file. If path is a directory, then the files in the directory are sorted by strverscmp(3); files that start with "." or without an .fstab extension are ignored. The option can be specified more than once. This option is mostly designed for initramfs or chroot scripts where additional configuration is specified beyond standard system configuration. Note that mount does not pass the option --fstab to the /sbin/mount.type helpers, meaning that the alternative fstab files will be invisible for the helpers. This is no problem for normal mounts, but user (non-root) mounts always require fstab to verify the users rights. -t, --types fstype The argument following the -t is used to indicate the filesystem type. The filesystem types which are currently supported depend on the running kernel. See /proc/filesystems and /lib/modules/$(uname -r)/kernel/fs for a complete list of the filesystems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs. The programs mount and umount(8) support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For example 'fuse.sshfs'. Its recommended to use subtype notation rather than add any prefix to the mount source (for example 'sshfs#example.com' is deprecated). If no -t option is given, or if the auto type is specified, mount will try to guess the desired type. mount uses the libblkid(3) library for guessing the filesystem type; if that does not turn up anything that looks familiar, mount will try to read the file /etc/filesystems, or, if that does not exist, /proc/filesystems. All of the filesystem types listed there will be tried, except for those that are labeled "nodev" (e.g. devpts, proc and nfs). If /etc/filesystems ends in a line with a single *, mount will read /proc/filesystems afterwards. While trying, all filesystem types will be mounted with the mount option silent. The auto type may be useful for user-mounted floppies. Creating a file /etc/filesystems can be useful to change the probe order (e.g., to try vfat before msdos or ext3 before ext2) or if you use a kernel module autoloader. More than one type may be specified in a comma-separated list, for the -t option as well as in an /etc/fstab entry. The list of filesystem types for the -t option can be prefixed with no to specify the filesystem types on which no action should be taken. The prefix no has no effect when specified in an /etc/fstab entry. The prefix no can be meaningful with the -a option. For example, the command mount -a -t nomsdos,smbfs mounts all filesystems except those of type msdos and smbfs. For most types all the mount program has to do is issue a simple mount(2) system call, and no detailed knowledge of the filesystem type is required. For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems have a separate mount program. In order to make it possible to treat all types in a uniform way, mount will execute the program /sbin/mount.type (if that exists) when called with type type. Since different versions of the smbmount program have different calling conventions, /sbin/mount.smbfs may have to be a shell script that sets up the desired call. -U, --uuid uuid Mount the partition that has the specified uuid. -v, --verbose Verbose mode. -w, --rw, --read-write Mount the filesystem read/write. Read-write is the kernel default and the mount default is to try read-only if the previous mount(2) syscall with read-write flags on write-protected devices failed. A synonym is -o rw. Note that specifying -w on the command line forces mount to never try read-only mount on write-protected devices or already mounted read-only filesystems. -h, --help Display help text and exit. -V, --version Print version and exit. FILESYSTEM-INDEPENDENT MOUNT OPTIONS top Some of these options are only useful when they appear in the /etc/fstab file. Some of these options could be enabled or disabled by default in the system kernel. To check the current setting see the options in /proc/mounts. Note that filesystems also have per-filesystem specific default mount options (see for example tune2fs -l output for extN filesystems). The options nosuid, noexec, nodiratime, relatime, noatime, strictatime, and nosymfollow are interpreted only by the abstract VFS kernel layer and applied to the mountpoint node rather than to the filesystem itself. Try: findmnt -o TARGET,VFS-OPTIONS,FS-OPTIONS to get a complete overview of filesystems and VFS options. The read-only setting (ro or rw) is interpreted by VFS and the filesystem and depends on how the option is specified on the mount(8) command line. The default is to interpret it on the filesystem level. The operation "-o bind,remount,ro" is applied only to the VFS mountpoint, and operation "-o remount,ro" is applied to VFS and filesystem superblock. This semantic allows create a read-only mountpoint but keeps the filesystem writable from another mountpoint. Since v2.39 libmount can use a new kernel mount interface to set the VFS options recursive. For backward compatibility, this feature is not enabled by default, although recursive operation (e.g. rbind) has been requested. The new option argument "recursive" could be specified, for example: mount -orbind,ro=recursive,noexec=recursive,nosuid /foo /bar recursively binds filesystems from /foo to /bar, /bar, and all submounts will be read-only and noexec, but only /bar itself will be "nosuid". The "recursive" optional argument for VFS mount options is an EXPERIMENTAL feature. The following options apply to any filesystem that is being mounted (but not every filesystem actually honors them - e.g., the sync option today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs): async All I/O to the filesystem should be done asynchronously. (See also the sync option.) atime Do not use the noatime feature, so the inode access time is controlled by kernel defaults. See also the descriptions of the relatime and strictatime mount options. noatime Do not update inode access times on this filesystem (e.g. for faster access on the news spool to speed up news servers). This works for all inode types (directories too), so it implies nodiratime. auto Can be mounted with the -a option. noauto Can only be mounted explicitly (i.e., the -a option will not cause the filesystem to be mounted). context=context, fscontext=context, defcontext=context, and rootcontext=context The context= option is useful when mounting filesystems that do not support extended attributes, such as a floppy or hard disk formatted with VFAT, or systems that are not normally running under SELinux, such as an ext3 or ext4 formatted disk from a non-SELinux workstation. You can also use context= on filesystems you do not trust, such as a floppy. It also helps in compatibility with xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where xattrs are supported, you can save time not having to label every file by assigning the entire disk one security context. A commonly used option for removable media is context="system_u:object_r:removable_t. The fscontext= option works for all filesystems, regardless of their xattr support. The fscontext option sets the overarching filesystem label to a specific security context. This filesystem label is separate from the individual labels on the files. It represents the entire filesystem for certain kinds of permission checks, such as during mount or file creation. Individual file labels are still obtained from the xattrs on the files themselves. The context option actually sets the aggregate context that fscontext provides, in addition to supplying the same label for individual files. You can set the default security context for unlabeled files using defcontext= option. This overrides the value set for unlabeled files in the policy and requires a filesystem that supports xattr labeling. The rootcontext= option allows you to explicitly label the root inode of a FS being mounted before that FS or inode becomes visible to userspace. This was found to be useful for things like stateless Linux. The special value @target can be used to assign the current context of the target mountpoint location. Note that the kernel rejects any remount request that includes the context option, even when unchanged from the current context. Warning: the context value might contain commas, in which case the value has to be properly quoted, otherwise mount will interpret the comma as a separator between mount options. Dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t tmpfs none /mnt -o \ 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec' For more details, see selinux(8). defaults Use the default options: rw, suid, dev, exec, auto, nouser, and async. Note that the real set of all default mount options depends on the kernel and filesystem type. See the beginning of this section for more details. dev Interpret character or block special devices on the filesystem. nodev Do not interpret character or block special devices on the filesystem. diratime Update directory inode access times on this filesystem. This is the default. (This option is ignored when noatime is set.) nodiratime Do not update directory inode access times on this filesystem. (This option is implied when noatime is set.) dirsync All directory updates within the filesystem should be done synchronously. This affects the following system calls: creat(2), link(2), unlink(2), symlink(2), mkdir(2), rmdir(2), mknod(2) and rename(2). exec Permit execution of binaries and other executable files. noexec Do not permit direct execution of any binaries on the mounted filesystem. group Allow an ordinary user to mount the filesystem if one of that users groups matches the group of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line group,dev,suid). iversion Every time the inode is modified, the i_version field will be incremented. noiversion Do not increment the i_version inode field. mand Allow mandatory locks on this filesystem. See fcntl(2). This option was deprecated in Linux 5.15. nomand Do not allow mandatory locks on this filesystem. _netdev The filesystem resides on a device that requires network access (used to prevent the system from attempting to mount these filesystems until the network has been enabled on the system). nofail Do not report errors for this device if it does not exist. relatime Update inode access times relative to modify or change time. Access time is only updated if the previous access time was earlier than or equal to the current modify or change time. (Similar to noatime, but it doesnt break mutt(1) or other applications that need to know if a file has been read since the last time it was modified.) Since Linux 2.6.30, the kernel defaults to the behavior provided by this option (unless noatime was specified), and the strictatime option is required to obtain traditional semantics. In addition, since Linux 2.6.30, the files last access time is always updated if it is more than 1 day old. norelatime Do not use the relatime feature. See also the strictatime mount option. strictatime Allows to explicitly request full atime updates. This makes it possible for the kernel to default to relatime or noatime but still allow userspace to override it. For more details about the default system mount options see /proc/mounts. nostrictatime Use the kernels default behavior for inode access time updates. lazytime Only update times (atime, mtime, ctime) on the in-memory version of the file inode. This mount option significantly reduces writes to the inode table for workloads that perform frequent random writes to preallocated files. The on-disk timestamps are updated only when: the inode needs to be updated for some change unrelated to file timestamps the application employs fsync(2), syncfs(2), or sync(2) an undeleted inode is evicted from memory more than 24 hours have passed since the inode was written to disk. nolazytime Do not use the lazytime feature. suid Honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. nosuid Do not honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. In addition, SELinux domain transitions require permission nosuid_transition, which in turn needs also policy capability nnp_nosuid_transition. silent Turn on the silent flag. loud Turn off the silent flag. owner Allow an ordinary user to mount the filesystem if that user is the owner of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line owner,dev,suid). remount Attempt to remount an already-mounted filesystem. This is commonly used to change the mount flags for a filesystem, especially to make a readonly filesystem writable. It does not change device or mount point. The remount operation together with the bind flag has special semantics. See above, the subsection Bind mount operation. The default kernel behavior for VFS mount flags (nodev,nosuid,noexec,ro) is to reset all unspecified flags on remount. Thats why mount(8) tries to keep the current setting according to fstab or /proc/self/mountinfo. This default behavior is possible to change by --options-mode. The recursive change of the mount flags (supported since v2.39 on systems with mount_setattr(2) syscall), for example, mount -o remount,ro=recursive, do not use "reset-unspecified" behavior, and it works as a simple add/remove operation and unspecified flags are not modified. The remount functionality follows the standard way the mount command works with options from fstab. This means that mount does not read fstab (or mtab) only when both device and dir are specified. mount -o remount,rw /dev/foo /dir After this call all old mount options are replaced and arbitrary stuff from fstab (or mtab) is ignored, except the loop= option which is internally generated and maintained by the mount command. mount -o remount,rw /dir After this call, mount reads fstab and merges these options with the options from the command line (-o). If no mountpoint is found in fstab, then it defaults to mount options from /proc/self/mountinfo. mount allows the use of --all to remount all already mounted filesystems which match a specified filter (-O and -t). For example: mount --all -o remount,ro -t vfat remounts all already mounted vfat filesystems in read-only mode. Each of the filesystems is remounted by mount -o remount,ro /dir semantic. This means the mount command reads fstab or mtab and merges these options with the options from the command line. ro Mount the filesystem read-only. rw Mount the filesystem read-write. sync All I/O to the filesystem should be done synchronously. In the case of media with a limited number of write cycles (e.g. some flash drives), sync may cause life-cycle shortening. user Allow an ordinary user to mount the filesystem. The name of the mounting user is written to the mtab file (or to the private libmount file in /run/mount on systems without a regular mtab) so that this same user can unmount the filesystem again. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line user,exec,dev,suid). nouser Forbid an ordinary user to mount the filesystem. This is the default; it does not imply any other options. users Allow any user to mount and to unmount the filesystem, even when some other ordinary user mounted it. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line users,exec,dev,suid). X-* All options prefixed with "X-" are interpreted as comments or as userspace application-specific options. These options are not stored in user space (e.g., mtab file), nor sent to the mount.type helpers nor to the mount(2) system call. The suggested format is X-appname.option. x-* The same as X-* options, but stored permanently in user space. This means the options are also available for umount(8) or other operations. Note that maintaining mount options in user space is tricky, because its necessary use libmount-based tools and there is no guarantee that the options will be always available (for example after a move mount operation or in unshared namespace). Note that before util-linux v2.30 the x-* options have not been maintained by libmount and stored in user space (functionality was the same as for X-* now), but due to the growing number of use-cases (in initrd, systemd etc.) the functionality has been extended to keep existing fstab configurations usable without a change. X-mount.auto-fstypes=list Specifies allowed or forbidden filesystem types for automatic filesystem detection. The list is a comma-separated list of the filesystem names. The automatic filesystem detection is triggered by the "auto" filesystem type or when the filesystem type is not specified. Thy list follows how mount evaluates type patterns (see -t for more details). Only specified filesystem types are allowed, or all specified types are forbidden if the list is prefixed by "no". For example, X-mount.auto-fstypes="ext4,btrfs" accepts only ext4 and btrfs, and X-mount.auto-fstypes="novfat,xfs" accepts all filesystems except vfat and xfs. Note that comma is used as a separator between mount options, it means that auto-fstypes values have to be properly quoted, dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t auto -oX-mount.auto-fstypes="noext2,ext3"' /dev/sdc1 /mnt/test X-mount.mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. The optional argument mode specifies the filesystem access mode used for mkdir(2) in octal notation. The default mode is 0755. This functionality is supported only for root users or when mount is executed without suid permissions. The option is also supported as x-mount.mkdir, but this notation is deprecated since v2.30. See also --mkdir command line option. X-mount.subdir=directory Allow mounting sub-directory from a filesystem instead of the root directory. For now, this feature is implemented by temporary filesystem root directory mount in unshared namespace and then bind the sub-directory to the final mount point and umount the root of the filesystem. The sub-directory mount shows up atomically for the rest of the system although it is implemented by multiple mount(2) syscalls. Note that this feature will not work in session with an unshared private mount namespace (after unshare --mount) on old kernels or with mount(8) without support for file-descriptors-based mount kernel API. In this case, you need unshare --mount --propagation shared. This feature is EXPERIMENTAL. X-mount.owner=username|UID, X-mount.group=group|GID Set mountpoint's ownership after mounting. Names resolved in the target mount namespace, see -N. X-mount.mode=mode Set mountpoint's mode after mounting. X-mount.idmap=id-type:id-mount:id-host:id-range [id-type:id-mount:id-host:id-range], X-mount.idmap=file Use this option to create an idmapped mount. An idmapped mount allows to change ownership of all files located under a mount according to the ID-mapping associated with a user namespace. The ownership change is tied to the lifetime and localized to the relevant mount. The relevant ID-mapping can be specified in two ways: A user can specify the ID-mapping directly. The ID-mapping must be specified using the syntax id-type:id-mount:id-host:id-range. Specifying u as the id-type prefix creates a UID-mapping, g creates a GID-mapping and omitting id-type or specifying b creates both a UID- and GID-mapping. The id-mount parameter indicates the starting ID in the new mount. The id-host parameter indicates the starting ID in the filesystem. The id-range parameter indicates how many IDs are to be mapped. It is possible to specify multiple ID-mappings. The individual ID-mappings must be separated by spaces. For example, the ID-mapping X-mount.idmap=u:1000:0:1 g:1001:1:2 5000:1000:2 creates an idmapped mount where UID 0 is mapped to UID 1000, GID 1 is mapped to GUID 1001, GID 2 is mapped to GID 1002, UID and GID 1000 are mapped to 5000, and UID and GID 1001 are mapped to 5001 in the mount. When an ID-mapping is specified directly a new user namespace will be allocated with the requested ID-mapping. The newly created user namespace will be attached to the mount. A user can specify a user namespace file. The user namespace will then be attached to the mount and the ID-mapping of the user namespace will become the ID-mapping of the mount. For example, X-mount.idmap=/proc/PID/ns/user will attach the user namespace of the process PID to the mount. nosymfollow Do not follow symlinks when resolving paths. Symlinks can still be created, and readlink(1), readlink(2), realpath(1), and realpath(3) all still work properly. FILESYSTEM-SPECIFIC MOUNT OPTIONS top This section lists options that are specific to particular filesystems. Where possible, you should first consult filesystem-specific manual pages for details. Some of those pages are listed in the following table. Filesystem(s) Manual page btrfs btrfs(5) cifs mount.cifs(8) ext2, ext3, ext4 ext4(5) fuse fuse(8) nfs nfs(5) tmpfs tmpfs(5) xfs xfs(5) Note that some of the pages listed above might be available only after you install the respective userland tools. The following options apply only to certain filesystems. We sort them by filesystem. All options follow the -o flag. What options are supported depends a bit on the running kernel. Further information may be available in filesystem-specific files in the kernel source subdirectory Documentation/filesystems. Mount options for adfs uid=value and gid=value Set the owner and group of the files in the filesystem (default: uid=gid=0). ownmask=value and othmask=value Set the permission mask for ADFS 'owner' permissions and 'other' permissions, respectively (default: 0700 and 0077, respectively). See also /usr/src/linux/Documentation/filesystems/adfs.rst. Mount options for affs uid=value and gid=value Set the owner and group of the root of the filesystem (default: uid=gid=0, but with option uid or gid without specified value, the UID and GID of the current process are taken). setuid=value and setgid=value Set the owner and group of all files. mode=value Set the mode of all files to value & 0777 disregarding the original permissions. Add search permission to directories that have read permission. The value is given in octal. protect Do not allow any changes to the protection bits on the filesystem. usemp Set UID and GID of the root of the filesystem to the UID and GID of the mount point upon the first sync or umount, and then clear this option. Strange... verbose Print an informational message for each successful mount. prefix=string Prefix used before volume name, when following a link. volume=string Prefix (of length at most 30) used before '/' when following a symbolic link. reserved=value (Default: 2.) Number of unused blocks at the start of the device. root=value Give explicitly the location of the root block. bs=value Give blocksize. Allowed values are 512, 1024, 2048, 4096. grpquota|noquota|quota|usrquota These options are accepted but ignored. (However, quota utilities may react to such strings in /etc/fstab.) Mount options for debugfs The debugfs filesystem is a pseudo filesystem, traditionally mounted on /sys/kernel/debug. As of kernel version 3.4, debugfs has the following options: uid=n, gid=n Set the owner and group of the mountpoint. mode=value Sets the mode of the mountpoint. Mount options for devpts The devpts filesystem is a pseudo filesystem, traditionally mounted on /dev/pts. In order to acquire a pseudo terminal, a process opens /dev/ptmx; the number of the pseudo terminal is then made available to the process and the pseudo terminal slave can be accessed as /dev/pts/<number>. uid=value and gid=value This sets the owner or the group of newly created pseudo terminals to the specified values. When nothing is specified, they will be set to the UID and GID of the creating process. For example, if there is a tty group with GID 5, then gid=5 will cause newly created pseudo terminals to belong to the tty group. mode=value Set the mode of newly created pseudo terminals to the specified value. The default is 0600. A value of mode=620 and gid=5 makes "mesg y" the default on newly created pseudo terminals. newinstance Create a private instance of the devpts filesystem, such that indices of pseudo terminals allocated in this new instance are independent of indices created in other instances of devpts. All mounts of devpts without this newinstance option share the same set of pseudo terminal indices (i.e., legacy mode). Each mount of devpts with the newinstance option has a private set of pseudo terminal indices. This option is mainly used to support containers in the Linux kernel. It is implemented in Linux kernel versions starting with 2.6.29. Further, this mount option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. To use this option effectively, /dev/ptmx must be a symbolic link to pts/ptmx. See Documentation/filesystems/devpts.txt in the Linux kernel source tree for details. ptmxmode=value Set the mode for the new ptmx device node in the devpts filesystem. With the support for multiple instances of devpts (see newinstance option above), each instance has a private ptmx node in the root of the devpts filesystem (typically /dev/pts/ptmx). For compatibility with older versions of the kernel, the default mode of the new ptmx node is 0000. ptmxmode=value specifies a more useful mode for the ptmx node and is highly recommended when the newinstance option is specified. This option is only implemented in Linux kernel versions starting with 2.6.29. Further, this option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. Mount options for fat (Note: fat is not a separate filesystem, but a common part of the msdos, umsdos and vfat filesystems.) blocksize={512|1024|2048} Set blocksize (default 512). This option is obsolete. uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. dmask=value Set the umask applied to directories only. The default is the umask of the current process. The value is given in octal. fmask=value Set the umask applied to regular files only. The default is the umask of the current process. The value is given in octal. allow_utime=value This option controls the permission check of mtime/atime. 20 If current process is in group of files group ID, you can change timestamp. 2 Other users can change timestamp. The default is set from 'dmask' option. (If the directory is writable, utime(2) is also allowed. I.e. ~dmask & 022) Normally utime(2) checks that the current process is owner of the file, or that it has the CAP_FOWNER capability. But FAT filesystems dont have UID/GID on disk, so the normal check is too inflexible. With this option you can relax it. check=value Three different levels of pickiness can be chosen: r[elaxed] Upper and lower case are accepted and equivalent, long name parts are truncated (e.g. verylongname.foobar becomes verylong.foo), leading and embedded spaces are accepted in each name part (name and extension). n[ormal] Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are rejected. This is the default. s[trict] Like "normal", but names that contain long parts or special characters that are sometimes used on Linux but are not accepted by MS-DOS (+, =, etc.) are rejected. codepage=value Sets the codepage for converting to shortname characters on FAT and VFAT filesystems. By default, codepage 437 is used. conv=mode This option is obsolete and may fail or be ignored. cvf_format=module Forces the driver to use the CVF (Compressed Volume File) module cvf_module instead of auto-detection. If the kernel supports kmod, the cvf_format=xxx option also controls on-demand CVF module loading. This option is obsolete. cvf_option=option Option passed to the CVF module. This option is obsolete. debug Turn on the debug flag. A version string and a list of filesystem parameters will be printed (these data are also printed if the parameters appear to be inconsistent). discard If set, causes discard/TRIM commands to be issued to the block device when blocks are freed. This is useful for SSD devices and sparse/thinly-provisioned LUNs. dos1xfloppy If set, use a fallback default BIOS Parameter Block configuration, determined by backing device size. These static parameters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images. errors={panic|continue|remount-ro} Specify FAT behavior on critical errors: panic, continue without doing anything, or remount the partition in read-only mode (default behavior). fat={12|16|32} Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT type detection routine. Use with caution! iocharset=value Character set to use for converting between 8 bit characters and 16 bit Unicode characters. The default is iso8859-1. Long filenames are stored on disk in Unicode format. nfs={stale_rw|nostale_ro} Enable this only if you want to export the FAT filesystem over NFS. stale_rw: This option maintains an index (cache) of directory inodes which is used by the nfs-related code to improve look-ups. Full file operations (read/write) over NFS are supported but with cache eviction at NFS server, this could result in spurious ESTALE errors. nostale_ro: This option bases the inode number and file handle on the on-disk location of a file in the FAT directory entry. This ensures that ESTALE will not be returned after a file is evicted from the inode cache. However, it means that operations such as rename, create and unlink could cause file handles that previously pointed at one file to point at a different file, potentially causing data corruption. For this reason, this option also mounts the filesystem readonly. To maintain backward compatibility, -o nfs is also accepted, defaulting to stale_rw. tz=UTC This option disables the conversion of timestamps between local time (as used by Windows on FAT) and UTC (which Linux uses internally). This is particularly useful when mounting devices (like digital cameras) that are set to UTC in order to avoid the pitfalls of local time. time_offset=minutes Set offset for conversion of timestamps from local time used by FAT to UTC. I.e., minutes will be subtracted from each timestamp to convert it to UTC used internally by Linux. This is useful when the time zone set in the kernel via settimeofday(2) is not the time zone used by the filesystem. Note that this option still does not provide correct time stamps in all cases in presence of DST - time stamps in a different DST setting will be off by one hour. quiet Turn on the quiet flag. Attempts to chown or chmod files do not return errors, although they fail. Use with caution! rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO of the directory will just be ignored, and is used only by applications as a flag (e.g. its set for the customized folder). If you want to use ATTR_RO as read-only flag even for the directory, set this option. showexec If set, the execute permission bits of the file will be allowed only if the extension part of the name is .EXE, .COM, or .BAT. Not set by default. sys_immutable If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux. Not set by default. flush If set, the filesystem will try to flush to disk more early than normal. Not set by default. usefree Use the "free clusters" value stored on FSINFO. Itll be used to determine number of free clusters without scanning disk. But its not used by default, because recent Windows dont update it correctly in some case. If you are sure the "free clusters" on FSINFO is correct, by this option you can avoid scanning disk. dots, nodots, dotsOK=[yes|no] Various misguided attempts to force Unix or DOS conventions onto a FAT filesystem. Mount options for hfs creator=cccc, type=cccc Set the creator/type values as shown by the MacOS finder used for creating new files. Default values: '????'. uid=n, gid=n Set the owner and group of all files. (Default: the UID and GID of the current process.) dir_umask=n, file_umask=n, umask=n Set the umask used for all directories, all regular files, or all files and directories. Defaults to the umask of the current process. session=n Select the CDROM session to mount. Defaults to leaving that decision to the CDROM driver. This option will fail with anything but a CDROM as underlying device. part=n Select partition number n from the device. Only makes sense for CDROMs. Defaults to not parsing the partition table at all. quiet Dont complain about invalid mount options. Mount options for hpfs uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. case={lower|asis} Convert all files names to lower case, or leave them. (Default: case=lower.) conv=mode This option is obsolete and may fail or being ignored. nocheck Do not abort mounting when certain consistency checks fail. Mount options for iso9660 ISO 9660 is a standard describing a filesystem structure to be used on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the udf filesystem.) Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like restrictions on filename length), and in addition all characters are in upper case. Also there is no field for file ownership, protection, number of links, provision for block/character devices, etc. Rock Ridge is an extension to iso9660 that provides all of these UNIX-like features. Basically there are extensions to each directory record that supply all of the additional information, and when Rock Ridge is in use, the filesystem is indistinguishable from a normal UNIX filesystem (except that it is read-only, of course). norock Disable the use of Rock Ridge extensions, even if available. Cf. map. nojoliet Disable the use of Microsoft Joliet extensions, even if available. Cf. map. check={r[elaxed]|s[trict]} With check=relaxed, a filename is first converted to lower case before doing the lookup. This is probably only meaningful together with norock and map=normal. (Default: check=strict.) uid=value and gid=value Give all files in the filesystem the indicated user or group id, possibly overriding the information found in the Rock Ridge extensions. (Default: uid=0,gid=0.) map={n[ormal]|o[ff]|a[corn]} For non-Rock Ridge volumes, normal name translation maps upper to lower case ASCII, drops a trailing ';1', and converts ';' to '.'. With map=off no name translation is done. See norock. (Default: map=normal.) map=acorn is like map=normal but also apply Acorn extensions if present. mode=value For non-Rock Ridge volumes, give all files the indicated mode. (Default: read and execute permission for everybody.) Octal mode values require a leading 0. unhide Also show hidden and associated files. (If the ordinary files and the associated or hidden files have the same filenames, this may make the ordinary files inaccessible.) block={512|1024|2048} Set the block size to the indicated value. (Default: block=1024.) conv=mode This option is obsolete and may fail or being ignored. cruft If the high byte of the file length contains other garbage, set this mount option to ignore the high order bits of the file length. This implies that a file cannot be larger than 16 MB. session=x Select number of session on a multisession CD. sbsector=xxx Session begins from sector xxx. The following options are the same as for vfat and specifying them only makes sense when using discs encoded using Microsofts Joliet extensions. iocharset=value Character set to use for converting 16 bit Unicode characters on CD to 8 bit characters. The default is iso8859-1. utf8 Convert 16 bit Unicode characters on CD to UTF-8. Mount options for jfs iocharset=name Character set to use for converting from Unicode to ASCII. The default is to do no conversion. Use iocharset=utf8 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in the kernel .config file. resize=value Resize the volume to value blocks. JFS only supports growing a volume, not shrinking it. This option is only valid during a remount, when the volume is mounted read-write. The resize keyword with no value will grow the volume to the full size of the partition. nointegrity Do not write to the journal. The primary use of this option is to allow for higher performance when restoring a volume from backup media. The integrity of the volume is not guaranteed if the system abnormally ends. integrity Default. Commit metadata changes to the journal. Use this option to remount a volume where the nointegrity option was previously specified in order to restore normal behavior. errors={continue|remount-ro|panic} Define the behavior when an error is encountered. (Either ignore errors and just mark the filesystem erroneous and continue, or remount the filesystem read-only, or panic and halt the system.) noquota|quota|usrquota|grpquota These options are accepted but ignored. Mount options for msdos See mount options for fat. If the msdos filesystem detects an inconsistency, it reports an error and sets the file system read-only. The filesystem can be made writable again by remounting it. Mount options for ncpfs Just like nfs, the ncpfs implementation expects a binary argument (a struct ncp_mount_data) to the mount(2) system call. This argument is constructed by ncpmount(8) and the current version of mount (2.12) does not know anything about ncpfs. Mount options for ntfs iocharset=name Character set to use when returning file names. Unlike VFAT, NTFS suppresses names that contain nonconvertible characters. Deprecated. nls=name New name for the option earlier called iocharset. utf8 Use UTF-8 for converting file names. uni_xlate={0|1|2} For 0 (or 'no' or 'false'), do not use escape sequences for unknown Unicode characters. For 1 (or 'yes' or 'true') or 2, use vfat-style 4-byte escape sequences starting with ":". Here 2 gives a little-endian encoding and 1 a byteswapped bigendian encoding. posix=[0|1] If enabled (posix=1), the filesystem distinguishes between upper and lower case. The 8.3 alias names are presented as hard links instead of being suppressed. This option is obsolete. uid=value, gid=value and umask=value Set the file permission on the filesystem. The umask value is given in octal. By default, the files are owned by root and not readable by somebody else. Mount options for overlay Since Linux 3.18 the overlay pseudo filesystem implements a union mount for other filesystems. An overlay filesystem combines two filesystems - an upper filesystem and a lower filesystem. When a name exists in both filesystems, the object in the upper filesystem is visible while the object in the lower filesystem is either hidden or, in the case of directories, merged with the upper object. The lower filesystem can be any filesystem supported by Linux and does not need to be writable. The lower filesystem can even be another overlayfs. The upper filesystem will normally be writable and if it is it must support the creation of trusted.* extended attributes, and must provide a valid d_type in readdir responses, so NFS is not suitable. A read-only overlay of two read-only filesystems may use any filesystem type. The options lowerdir and upperdir are combined into a merged directory by using: mount -t overlay overlay \ -olowerdir=/lower,upperdir=/upper,workdir=/work /merged lowerdir=directory Any filesystem, does not need to be on a writable filesystem. upperdir=directory The upperdir is normally on a writable filesystem. workdir=directory The workdir needs to be an empty directory on the same filesystem as upperdir. userxattr Use the "user.overlay." xattr namespace instead of "trusted.overlay.". This is useful for unprivileged mounting of overlayfs. redirect_dir={on|off|follow|nofollow} If the redirect_dir feature is enabled, then the directory will be copied up (but not the contents). Then the "{trusted|user}.overlay.redirect" extended attribute is set to the path of the original location from the root of the overlay. Finally the directory is moved to the new location. on Redirects are enabled. off Redirects are not created and only followed if "redirect_always_follow" feature is enabled in the kernel/module config. follow Redirects are not created, but followed. nofollow Redirects are not created and not followed (equivalent to "redirect_dir=off" if "redirect_always_follow" feature is not enabled). index={on|off} Inode index. If this feature is disabled and a file with multiple hard links is copied up, then this will "break" the link. Changes will not be propagated to other names referring to the same inode. uuid={on|off} Can be used to replace UUID of the underlying filesystem in file handles with null, and effectively disable UUID checks. This can be useful in case the underlying disk is copied and the UUID of this copy is changed. This is only applicable if all lower/upper/work directories are on the same filesystem, otherwise it will fallback to normal behaviour. nfs_export={on|off} When the underlying filesystems supports NFS export and the "nfs_export" feature is enabled, an overlay filesystem may be exported to NFS. With the "nfs_export" feature, on copy_up of any lower object, an index entry is created under the index directory. The index entry name is the hexadecimal representation of the copy up origin file handle. For a non-directory object, the index entry is a hard link to the upper inode. For a directory object, the index entry has an extended attribute "{trusted|user}.overlay.upper" with an encoded file handle of the upper directory inode. When encoding a file handle from an overlay filesystem object, the following rules apply For a non-upper object, encode a lower file handle from lower inode For an indexed object, encode a lower file handle from copy_up origin For a pure-upper object and for an existing non-indexed upper object, encode an upper file handle from upper inode The encoded overlay file handle includes Header including path type information (e.g. lower/upper) UUID of the underlying filesystem Underlying filesystem encoding of underlying inode This encoding format is identical to the encoding format of file handles that are stored in extended attribute "{trusted|user}.overlay.origin". When decoding an overlay file handle, the following steps are followed Find underlying layer by UUID and path type information. Decode the underlying filesystem file handle to underlying dentry. For a lower file handle, lookup the handle in index directory by name. If a whiteout is found in index, return ESTALE. This represents an overlay object that was deleted after its file handle was encoded. For a non-directory, instantiate a disconnected overlay dentry from the decoded underlying dentry, the path type and index inode, if found. For a directory, use the connected underlying decoded dentry, path type and index, to lookup a connected overlay dentry. Decoding a non-directory file handle may return a disconnected dentry. copy_up of that disconnected dentry will create an upper index entry with no upper alias. When overlay filesystem has multiple lower layers, a middle layer directory may have a "redirect" to lower directory. Because middle layer "redirects" are not indexed, a lower file handle that was encoded from the "redirect" origin directory, cannot be used to find the middle or upper layer directory. Similarly, a lower file handle that was encoded from a descendant of the "redirect" origin directory, cannot be used to reconstruct a connected overlay path. To mitigate the cases of directories that cannot be decoded from a lower file handle, these directories are copied up on encode and encoded as an upper file handle. On an overlay filesystem with no upper layer this mitigation cannot be used NFS export in this setup requires turning off redirect follow (e.g. "redirect_dir=nofollow"). The overlay filesystem does not support non-directory connectable file handles, so exporting with the subtree_check exportfs configuration will cause failures to lookup files over NFS. When the NFS export feature is enabled, all directory index entries are verified on mount time to check that upper file handles are not stale. This verification may cause significant overhead in some cases. Note: the mount options index=off,nfs_export=on are conflicting for a read-write mount and will result in an error. xino={on|off|auto} The "xino" feature composes a unique object identifier from the real object st_ino and an underlying fsid index. The "xino" feature uses the high inode number bits for fsid, because the underlying filesystems rarely use the high inode number bits. In case the underlying inode number does overflow into the high xino bits, overlay filesystem will fall back to the non xino behavior for that inode. For a detailed description of the effect of this option please refer to https://docs.kernel.org/filesystems/overlayfs.html metacopy={on|off} When metadata only copy up feature is enabled, overlayfs will only copy up metadata (as opposed to whole file), when a metadata specific operation like chown/chmod is performed. Full file will be copied up later when file is opened for WRITE operation. In other words, this is delayed data copy up operation and data is copied up when there is a need to actually modify data. volatile Volatile mounts are not guaranteed to survive a crash. It is strongly recommended that volatile mounts are only used if data written to the overlay can be recreated without significant effort. The advantage of mounting with the "volatile" option is that all forms of sync calls to the upper filesystem are omitted. In order to avoid a giving a false sense of safety, the syncfs (and fsync) semantics of volatile mounts are slightly different than that of the rest of VFS. If any writeback error occurs on the upperdirs filesystem after a volatile mount takes place, all sync functions will return an error. Once this condition is reached, the filesystem will not recover, and every subsequent sync call will return an error, even if the upperdir has not experience a new error since the last sync call. When overlay is mounted with "volatile" option, the directory "$workdir/work/incompat/volatile" is created. During next mount, overlay checks for this directory and refuses to mount if present. This is a strong indicator that user should throw away upper and work directories and create fresh one. In very limited cases where the user knows that the system has not crashed and contents of upperdir are intact, The "volatile" directory can be removed. Mount options for reiserfs Reiserfs is a journaling filesystem. conv Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem, using the 3.6 format for newly created objects. This filesystem will no longer be compatible with reiserfs 3.5 tools. hash={rupasov|tea|r5|detect} Choose which hash function reiserfs will use to find files within directories. rupasov A hash invented by Yury Yu. Rupasov. It is fast and preserves locality, mapping lexicographically close file names to close hash values. This option should not be used, as it causes a high probability of hash collisions. tea A Davis-Meyer function implemented by Jeremy Fitzhardinge. It uses hash permuting bits in the name. It gets high randomness and, therefore, low probability of hash collisions at some CPU cost. This may be used if EHASHCOLLISION errors are experienced with the r5 hash. r5 A modified version of the rupasov hash. It is used by default and is the best choice unless the filesystem has huge directories and unusual file-name patterns. detect Instructs mount to detect which hash function is in use by examining the filesystem being mounted, and to write this information into the reiserfs superblock. This is only useful on the first mount of an old format filesystem. hashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. no_unhashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. noborder Disable the border allocator algorithm invented by Yury Yu. Rupasov. This may provide performance improvements in some situations. nolog Disable journaling. This will provide slight performance improvements in some situations at the cost of losing reiserfss fast recovery from crashes. Even with this option turned on, reiserfs still performs all journaling operations, save for actual writes into its journaling area. Implementation of nolog is a work in progress. notail By default, reiserfs stores small files and 'file tails' directly into its tree. This confuses some utilities such as lilo(8). This option is used to disable packing of files into the tree. replayonly Replay the transactions which are in the journal, but do not actually mount the filesystem. Mainly used by reiserfsck. resize=number A remount option which permits online expansion of reiserfs partitions. Instructs reiserfs to assume that the device has number blocks. This option is designed for use with devices which are under logical volume management (LVM). There is a special resizer utility which can be obtained from ftp://ftp.namesys.com/pub/reiserfsprogs. user_xattr Enable Extended User Attributes. See the attr(1) manual page. acl Enable POSIX Access Control Lists. See the acl(5) manual page. barrier=none / barrier=flush This disables / enables the use of write barriers in the journaling code. barrier=none disables, barrier=flush enables (default). This also requires an IO stack which can support barriers, and if reiserfs gets an error on a barrier write, it will disable barriers again with a warning. Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance penalty. If your disks are battery-backed in one way or another, disabling barriers may safely improve performance. Mount options for ubifs UBIFS is a flash filesystem which works on top of UBI volumes. Note that atime is not supported and is always turned off. The device name may be specified as ubiX_Y UBI device number X, volume number Y ubiY UBI device number 0, volume number Y ubiX:NAME UBI device number X, volume with name NAME ubi:NAME UBI device number 0, volume with name NAME Alternative ! separator may be used instead of :. The following mount options are available: bulk_read Enable bulk-read. VFS read-ahead is disabled because it slows down the filesystem. Bulk-Read is an internal optimization. Some flashes may read faster if the data are read at one go, rather than at several read requests. For example, OneNAND can do "read-while-load" if it reads more than one NAND page. no_bulk_read Do not bulk-read. This is the default. chk_data_crc Check data CRC-32 checksums. This is the default. no_chk_data_crc Do not check data CRC-32 checksums. With this option, the filesystem does not check CRC-32 checksum for data, but it does check it for the internal indexing information. This option only affects reading, not writing. CRC-32 is always calculated when writing the data. compr={none|lzo|zlib} Select the default compressor which is used when new files are written. It is still possible to read compressed files if mounted with the none option. Mount options for udf UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical Storage Technology Association, and is often used for DVD-ROM, frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, however, perfectly usable by itself on disk drives, flash drives and other block devices. See also iso9660. uid= Make all files in the filesystem belong to the given user. uid=forget can be specified independently of (or usually in addition to) uid=<user> and results in UDF not storing uids to the media. In fact the recorded uid is the 32-bit overflow uid -1 as defined by the UDF standard. The value is given as either <user> which is a valid user name or the corresponding decimal user id, or the special string "forget". gid= Make all files in the filesystem belong to the given group. gid=forget can be specified independently of (or usually in addition to) gid=<group> and results in UDF not storing gids to the media. In fact the recorded gid is the 32-bit overflow gid -1 as defined by the UDF standard. The value is given as either <group> which is a valid group name or the corresponding decimal group id, or the special string "forget". umask= Mask out the given permissions from all inodes read from the filesystem. The value is given in octal. mode= If mode= is set the permissions of all non-directory inodes read from the filesystem will be set to the given mode. The value is given in octal. dmode= If dmode= is set the permissions of all directory inodes read from the filesystem will be set to the given dmode. The value is given in octal. bs= Set the block size. Default value prior to kernel version 2.6.30 was 2048. Since 2.6.30 and prior to 4.11 it was logical device block size with fallback to 2048. Since 4.11 it is logical block size with fallback to any valid block size between logical device block size and 4096. For other details see the mkudffs(8) 2.0+ manpage, see the COMPATIBILITY and BLOCK SIZE sections. unhide Show otherwise hidden files. undelete Show deleted files in lists. adinicb Embed data in the inode. (default) noadinicb Dont embed data in the inode. shortad Use short UDF address descriptors. longad Use long UDF address descriptors. (default) nostrict Unset strict conformance. iocharset= Set the NLS character set. This requires kernel compiled with CONFIG_UDF_NLS option. utf8 Set the UTF-8 character set. Mount options for debugging and disaster recovery novrs Ignore the Volume Recognition Sequence and attempt to mount anyway. session= Select the session number for multi-session recorded optical media. (default= last session) anchor= Override standard anchor location. (default= 256) lastblock= Set the last block of the filesystem. Unused historical mount options that may be encountered and should be removed uid=ignore Ignored, use uid=<user> instead. gid=ignore Ignored, use gid=<group> instead. volume= Unimplemented and ignored. partition= Unimplemented and ignored. fileset= Unimplemented and ignored. rootdir= Unimplemented and ignored. Mount options for ufs ufstype=value UFS is a filesystem widely used in different operating systems. The problem are differences among implementations. Features of some implementations are undocumented, so its hard to recognize the type of ufs automatically. Thats why the user must specify the type of ufs by mount option. Possible values are: old Old format of ufs, this is the default, read only. (Dont forget to give the -r option.) 44bsd For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD). ufs2 Used in FreeBSD 5.x supported as read-write. 5xbsd Synonym for ufs2. sun For filesystems created by SunOS or Solaris on Sparc. sunx86 For filesystems created by Solaris on x86. hp For filesystems created by HP-UX, read-only. nextstep For filesystems created by NeXTStep (on NeXT station) (currently read only). nextstep-cd For NextStep CDROMs (block_size == 2048), read-only. openstep For filesystems created by OpenStep (currently read only). The same filesystem type is also used by macOS. onerror=value Set behavior on error: panic If an error is encountered, cause a kernel panic. [lock|umount|repair] These mount options dont do anything at present; when an error is encountered only a console message is printed. Mount options for umsdos See mount options for msdos. The dotsOK option is explicitly killed by umsdos. Mount options for vfat First of all, the mount options for fat are recognized. The dotsOK option is explicitly killed by vfat. Furthermore, there are uni_xlate Translate unhandled Unicode characters to special escaped sequences. This lets you backup and restore filenames that are created with any Unicode characters. Without this option, a '?' is used when no translation is possible. The escape character is ':' because it is otherwise invalid on the vfat filesystem. The escape sequence that gets used, where u is the Unicode character, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12). posix Allow two files with names that only differ in case. This option is obsolete. nonumtail First try to make a short name without sequence number, before trying name~num.ext. utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the console. It can be enabled for the filesystem with this option or disabled with utf8=0, utf8=no or utf8=false. If uni_xlate gets set, UTF8 gets disabled. shortname=mode Defines the behavior for creation and display of filenames which fit into 8.3 characters. If a long name for a file exists, it will always be the preferred one for display. There are four modes: lower Force the short name to lower case upon display; store a long name when the short name is not all upper case. win95 Force the short name to upper case upon display; store a long name when the short name is not all upper case. winnt Display the short name as is; store a long name when the short name is not all lower case or all upper case. mixed Display the short name as is; store a long name when the short name is not all upper case. This mode is the default since Linux 2.6.32. Mount options for usbfs devuid=uid and devgid=gid and devmode=mode Set the owner and group and mode of the device files in the usbfs filesystem (default: uid=gid=0, mode=0644). The mode is given in octal. busuid=uid and busgid=gid and busmode=mode Set the owner and group and mode of the bus directories in the usbfs filesystem (default: uid=gid=0, mode=0555). The mode is given in octal. listuid=uid and listgid=gid and listmode=mode Set the owner and group and mode of the file devices (default: uid=gid=0, mode=0444). The mode is given in octal. DM-VERITY SUPPORT top The device-mapper verity target provides read-only transparent integrity checking of block devices using kernel crypto API. The mount command can open the dm-verity device and do the integrity verification before the device filesystem is mounted. Requires libcryptsetup with in libmount (optionally via dlopen(3)). If libcryptsetup supports extracting the root hash of an already mounted device, existing devices will be automatically reused in case of a match. Mount options for dm-verity: verity.hashdevice=path Path to the hash tree device associated with the source volume to pass to dm-verity. verity.roothash=hex Hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothashfile. verity.roothashfile=path Path to file containing the hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothash. verity.hashoffset=offset If the hash tree device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the tree. verity.fecdevice=path Path to the Forward Error Correction (FEC) device associated with the source volume to pass to dm-verity. Optional. Requires kernel built with CONFIG_DM_VERITY_FEC. verity.fecoffset=offset If the FEC device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the FEC area. Optional. verity.fecroots=value Parity bytes for FEC (default: 2). Optional. verity.roothashsig=path Path to pkcs7(1ssl) signature of root hash hex string. Requires crypt_activate_by_signed_key() from cryptsetup and kernel built with CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG. For device reuse, signatures have to be either used by all mounts of a device or by none. Optional. verity.oncorruption=ignore|restart|panic Instruct the kernel to ignore, reboot or panic when corruption is detected. By default the I/O operation simply fails. Requires Linux 4.1 or newer, and libcrypsetup 2.3.4 or newer. Optional. Supported since util-linux v2.35. For example commands: mksquashfs /etc /tmp/etc.raw veritysetup format /tmp/etc.raw /tmp/etc.verity --root-hash-file=/tmp/etc.roothash openssl smime -sign -in /tmp/etc.roothash -nocerts -inkey private.key \ -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s mount -o verity.hashdevice=/tmp/etc.verity,verity.roothashfile=/tmp/etc.roothash,\ verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.raw /mnt create squashfs image from /etc directory, verity hash device and mount verified filesystem image to /mnt. The kernel will verify that the root hash is signed by a key from the kernel keyring if roothashsig is used. LOOP-DEVICE SUPPORT top One further possible type is a mount via the loop device. For example, the command mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3 will set up the loop device /dev/loop3 to correspond to the file /tmp/disk.img, and then mount this device on /mnt. If no explicit loop device is mentioned (but just an option '-o loop' is given), then mount will try to find some unused loop device and use that, for example mount /tmp/disk.img /mnt -o loop The mount command automatically creates a loop device from a regular file if a filesystem type is not specified or the filesystem is known for libblkid, for example: mount /tmp/disk.img /mnt mount -t ext4 /tmp/disk.img /mnt This type of mount knows about three options, namely loop, offset and sizelimit, that are really options to losetup(8). (These options can be used in addition to those specific to the filesystem type.) Since Linux 2.6.25 auto-destruction of loop devices is supported, meaning that any loop device allocated by mount will be freed by umount independently of /etc/mtab. You can also free a loop device by hand, using losetup -d or umount -d. Since util-linux v2.29, mount re-uses the loop device rather than initializing a new device if the same backing file is already used for some loop device with the same offset and sizelimit. This is necessary to avoid a filesystem corruption. EXIT STATUS top mount has the following exit status values (the bits can be ORed): 0 success 1 incorrect invocation or permissions 2 system error (out of memory, cannot fork, no more loop devices) 4 internal mount bug 8 user interrupt 16 problems writing or locking /etc/mtab 32 mount failure 64 some mount succeeded The command mount -a returns 0 (all succeeded), 32 (all failed), or 64 (some failed, some succeeded). EXTERNAL HELPERS top The syntax of external mount helpers is: /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t type.subtype] where the suffix is the filesystem type and the -sfnvoN options have the same meaning as the normal mount options. The -t option is used for filesystems with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs). The command mount does not pass the mount options unbindable, runbindable, private, rprivate, slave, rslave, shared, rshared, auto, noauto, comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers. All other options are used in a comma-separated list as an argument to the -o option. ENVIRONMENT top LIBMOUNT_FORCE_MOUNT2={always|never|auto} force to use classic mount(2) system call (requires support for new file descriptors based mount API). The default is auto; in this case, libmount tries to be smart and use classic mount(2) only for well-known issues. If the new mount API is unavailable, libmount can still use traditional mount(2), although LIBMOUNT_FORCE_MOUNT2 is set to never. LIBMOUNT_FSTAB=<path> overrides the default location of the fstab file (ignored for suid) LIBMOUNT_DEBUG=all enables libmount debug output LIBBLKID_DEBUG=all enables libblkid debug output LOOPDEV_DEBUG=all enables loop device setup debug output FILES top See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section above. /etc/fstab filesystem table /run/mount libmount private runtime directory /etc/mtab table of mounted filesystems or symlink to /proc/mounts /etc/mtab~ lock file (unused on systems with mtab symlink) /etc/mtab.tmp temporary file (unused on systems with mtab symlink) /etc/filesystems a list of filesystem types to try HISTORY top A mount command existed in Version 5 AT&T UNIX. BUGS top It is possible for a corrupted filesystem to cause a crash. Some Linux filesystems dont support -o sync and -o dirsync (the ext2, ext3, ext4, fat and vfat filesystems do support synchronous updates (a la BSD) when mounted with the sync option). The -o remount may not be able to change mount parameters (all ext2fs-specific parameters, except sb, are changeable with a remount, for example, but you cant change gid or umask for the fatfs). It is possible that the files /etc/mtab and /proc/mounts dont match on systems with a regular mtab file. The first file is based only on the mount command options, but the content of the second file also depends on the kernel and others settings (e.g. on a remote NFS server in certain cases the mount command may report unreliable information about an NFS mount point and the /proc/mount file usually contains more reliable information.) This is another reason to replace the mtab file with a symlink to the /proc/mounts file. Checking files on NFS filesystems referenced by file descriptors (i.e. the fcntl and ioctl families of functions) may lead to inconsistent results due to the lack of a consistency check in the kernel even if the noac mount option is used. The loop option with the offset or sizelimit options used may fail when using older kernels if the mount command cant confirm that the size of the block device has been configured as requested. This situation can be worked around by using the losetup(8) command manually before calling mount with the configured loop device. AUTHORS top Karel Zak <kzak@redhat.com> SEE ALSO top mount(2), umount(2), filesystems(5), fstab(5), nfs(5), xfs(5), mount_namespaces(7), xattr(7), e2label(8), findmnt(8), losetup(8), lsblk(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8), umount(8), xfs_admin(8) REPORTING BUGS top For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY top The mount command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at https://www.kernel.org/pub/linux/utils/util-linux/. If you have a bug report for this manual page, send it to util-linux@vger.kernel.org. This page was obtained from the project's upstream Git repository git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org util-linux 2.39.594-1e0ad 2023-08-25 MOUNT(8) Pages that refer to this page: eject(1), fusermount3(1), homectl(1), mountpoint(1), quotasync(1), systemd-dissect(1), systemd-mount(1), unshare(1), chown(2), fcntl(2), fsync(2), ioctl_iflags(2), mount(2), open(2), open_by_handle_at(2), umount(2), getmntent(3), getsubopt(3), fd(4), hd(4), loop(4), ram(4), autofs(5), ext4(5), filesystems(5), fstab(5), lxc.container.conf(5), nfs(5), nfsmount.conf(5), proc(5), repart.d(5), systemd.automount(5), systemd.exec(5), systemd.mount(5), tmpfs(5), xfs(5), bootparam(7), fanotify(7), file-hierarchy(7), hier(7), inode(7), man-pages(7), mount_namespaces(7), spufs(7), automount(8), blkid(8), btrfs-subvolume(8), e4crypt(8), e4defrag(8), findmnt(8), fsck.cramfs(8), fsck.xfs(8), fsfreeze(8), fstrim(8), lsof(8), mkfs.cramfs(8), mount(8), mount.fuse3(8), mount.nfs(8), pam_namespace(8), pivot_root(8), quotaon(8), swapon(8), switch_root(8), systemd-remount-fs.service(8), tune2fs(8), umount(8), wipefs(8), xfs_admin(8), xfs_db(8), xfs_freeze(8), xfs_growfs(8), xfs_info(8), xfs_logprint(8), xfs_rtcp(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if "/path/to/dir" is a nfs mount point Bash Command:<START>mount -l | grep 'type nfs' | sed 's/.* on \([^ ]*\) .*/\1/' | grep /path/to/dir<END>

Check if "\[$VLABEL\]" is mounted and save the result in variable "AMV"

AMV=$(mount -l | grep "\[$VLABEL\]")

['grep', 'mount']

Output a Bash command to accomplish the following task. Task: Check if "\[$VLABEL\]" is mounted and save the result in variable "AMV" Bash Command:<START>AMV=$(mount -l | grep "\[$VLABEL\]")<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # mount\n\n> Provides access to an entire filesystem in one directory.\n> More information: <https://manned.org/mount.8>.\n\n- Show all mounted filesystems:\n\n`mount`\n\n- Mount a device to a directory:\n\n`mount -t {{filesystem_type}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Create a specific directory if it does not exist and mount a device to it:\n\n`mount --mkdir {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a device to a directory for a specific user:\n\n`mount -o uid={{user_id}},gid={{group_id}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a CD-ROM device (with the filetype ISO9660) to `/cdrom` (readonly):\n\n`mount -t {{iso9660}} -o ro {{/dev/cdrom}} {{/cdrom}}`\n\n- Mount all the filesystem defined in `/etc/fstab`:\n\n`mount -a`\n\n- Mount a specific filesystem described in `/etc/fstab` (e.g. `/dev/sda1 /my_drive ext2 defaults 0 2`):\n\n`mount {{/my_drive}}`\n\n- Mount a directory to another directory:\n\n`mount --bind {{path/to/old_dir}} {{path/to/new_dir}}`\n Task: Check if "\[$VLABEL\]" is mounted and save the result in variable "AMV" Bash Command:<START>AMV=$(mount -l | grep "\[$VLABEL\]")<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. mount(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training mount(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND-LINE OPTIONS | FILESYSTEM-INDEPENDENT MOUNT OPTIONS | FILESYSTEM-SPECIFIC MOUNT OPTIONS | DM-VERITY SUPPORT | LOOP-DEVICE SUPPORT | EXIT STATUS | EXTERNAL HELPERS | ENVIRONMENT | FILES | HISTORY | BUGS | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY MOUNT(8) System Administration MOUNT(8) NAME top mount - mount a filesystem SYNOPSIS top mount [-h|-V] mount [-l] [-t fstype] mount -a [-fFnrsvw] [-t fstype] [-O optlist] mount [-fnrsvw] [-o options] device|mountpoint mount [-fnrsvw] [-t fstype] [-o options] device mountpoint mount --bind|--rbind|--move olddir newdir mount --make-[shared|slave|private|unbindable|rshared|rslave|rprivate|runbindable] mountpoint DESCRIPTION top All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the filesystem found on some device to the big file tree. Conversely, the umount(8) command will detach it again. The filesystem is used to control how data is stored on the device or provided in a virtual way by network or other services. The standard form of the mount command is: mount -t type device dir This tells the kernel to attach the filesystem found on device (which is of type type) at the directory dir. The option -t type is optional. The mount command is usually able to detect a filesystem. The root permissions are necessary to mount a filesystem by default. See section "Non-superuser mounts" below for more details. The previous contents (if any) and owner and mode of dir become invisible, and as long as this filesystem remains mounted, the pathname dir refers to the root of the filesystem on device. If only the directory or the device is given, for example: mount /dir then mount looks for a mountpoint (and if not found then for a device) in the /etc/fstab file. Its possible to use the --target or --source options to avoid ambiguous interpretation of the given argument. For example: mount --target /mountpoint The same filesystem may be mounted more than once, and in some cases (e.g., network filesystems) the same filesystem may be mounted on the same mountpoint multiple times. The mount command does not implement any policy to control this behavior. All behavior is controlled by the kernel and it is usually specific to the filesystem driver. The exception is --all, in this case already mounted filesystems are ignored (see --all below for more details). Listing the mounts The listing mode is maintained for backward compatibility only. For more robust and customizable output use findmnt(8), especially in your scripts. Note that control characters in the mountpoint name are replaced with '?'. The following command lists all mounted filesystems (of type type): mount [-l] [-t type] The option -l adds labels to this listing. See below. Indicating the device and filesystem Most devices are indicated by a filename (of a block special device), like /dev/sda1, but there are other possibilities. For example, in the case of an NFS mount, device may look like knuth.cwi.nl:/dir. The device names of disk partitions are unstable; hardware reconfiguration, and adding or removing a device can cause changes in names. This is the reason why its strongly recommended to use filesystem or partition identifiers like UUID or LABEL. Currently supported identifiers (tags): LABEL=label Human readable filesystem identifier. See also -L. UUID=uuid Filesystem universally unique identifier. The format of the UUID is usually a series of hex digits separated by hyphens. See also -U. Note that mount uses UUIDs as strings. The UUIDs from the command line or from fstab(5) are not converted to internal binary representation. The string representation of the UUID should be based on lower case characters. PARTLABEL=label Human readable partition identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). PARTUUID=uuid Partition universally unique identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). ID=id Hardware block device ID as generated by udevd. This identifier is usually based on WWN (unique storage identifier) and assigned by the hardware manufacturer. See ls /dev/disk/by-id for more details, this directory and running udevd is required. This identifier is not recommended for generic use as the identifier is not strictly defined and it depends on udev, udev rules and hardware. The command lsblk --fs provides an overview of filesystems, LABELs and UUIDs on available block devices. The command blkid -p <device> provides details about a filesystem on the specified device. Dont forget that there is no guarantee that UUIDs and labels are really unique, especially if you move, share or copy the device. Use lsblk -o +UUID,PARTUUID to verify that the UUIDs are really unique in your system. The recommended setup is to use tags (e.g. UUID=uuid) rather than /dev/disk/by-{label,uuid,id,partuuid,partlabel} udev symlinks in the /etc/fstab file. Tags are more readable, robust and portable. The mount(8) command internally uses udev symlinks, so the use of symlinks in /etc/fstab has no advantage over tags. For more details see libblkid(3). The proc filesystem is not associated with a special device, and when mounting it, an arbitrary keyword - for example, proc - can be used instead of a device specification. (The customary choice none is less fortunate: the error message 'none already mounted' from mount can be confusing.) The files /etc/fstab, /etc/mtab and /proc/mounts The file /etc/fstab (see fstab(5)), may contain lines describing what devices are usually mounted where, using which options. The default location of the fstab(5) file can be overridden with the --fstab path command-line option (see below for more details). The command mount -a [-t type] [-O optlist] (usually given in a bootscript) causes all filesystems mentioned in fstab (of the proper type and/or having or not having the proper options) to be mounted as indicated, except for those whose line contains the noauto keyword. Adding the -F option will make mount fork, so that the filesystems are mounted in parallel. When mounting a filesystem mentioned in fstab or mtab, it suffices to specify on the command line only the device, or only the mount point. The programs mount and umount(8) traditionally maintained a list of currently mounted filesystems in the file /etc/mtab. The support for regular classic /etc/mtab is completely disabled at compile time by default, because on current Linux systems it is better to make /etc/mtab a symlink to /proc/mounts instead. The regular mtab file maintained in userspace cannot reliably work with namespaces, containers and other advanced Linux features. If the regular mtab support is enabled, then its possible to use the file as well as the symlink. If no arguments are given to mount, the list of mounted filesystems is printed. If you want to override mount options from /etc/fstab, you have to use the -o option: mount device|dir -o options and then the mount options from the command line will be appended to the list of options from /etc/fstab. This default behaviour can be changed using the --options-mode command-line option. The usual behavior is that the last option wins if there are conflicting ones. The mount program does not read the /etc/fstab file if both device (or LABEL, UUID, ID, PARTUUID or PARTLABEL) and dir are specified. For example, to mount device foo at /dir: mount /dev/foo /dir This default behaviour can be changed by using the --options-source-force command-line option to always read configuration from fstab. For non-root users mount always reads the fstab configuration. Non-superuser mounts Normally, only the superuser can mount filesystems. However, when fstab contains the user option on a line, anybody can mount the corresponding filesystem. Thus, given a line /dev/cdrom /cd iso9660 ro,user,noauto,unhide any user can mount the iso9660 filesystem found on an inserted CDROM using the command: mount /cd Note that mount is very strict about non-root users and all paths specified on command line are verified before fstab is parsed or a helper program is executed. Its strongly recommended to use a valid mountpoint to specify filesystem, otherwise mount may fail. For example its a bad idea to use NFS or CIFS source on command line. Since util-linux 2.35, mount does not exit when user permissions are inadequate according to libmounts internal security rules. Instead, it drops suid permissions and continues as regular non-root user. This behavior supports use-cases where root permissions are not necessary (e.g., fuse filesystems, user namespaces, etc). For more details, see fstab(5). Only the user that mounted a filesystem can unmount it again. If any user should be able to unmount it, then use users instead of user in the fstab line. The owner option is similar to the user option, with the restriction that the user must be the owner of the special file. This may be useful e.g. for /dev/fd if a login script makes the console user owner of this device. The group option is similar, with the restriction that the user must be a member of the group of the special file. The user mount option is accepted if no username is specified. If used in the format user=someone, the option is silently ignored and visible only for external mount helpers (/sbin/mount.<type>) for compatibility with some network filesystems. Bind mount operation Remount part of the file hierarchy somewhere else. The call is: mount --bind olddir newdir or by using this fstab entry: /olddir /newdir none bind After this call the same contents are accessible in two places. It is important to understand that "bind" does not create any second-class or special node in the kernel VFS. The "bind" is just another operation to attach a filesystem. There is nowhere stored information that the filesystem has been attached by a "bind" operation. The olddir and newdir are independent and the olddir may be unmounted. One can also remount a single file (on a single file). Its also possible to use a bind mount to create a mountpoint from a regular directory, for example: mount --bind foo foo The bind mount call attaches only (part of) a single filesystem, not possible submounts. The entire file hierarchy including submounts can be attached a second place by using: mount --rbind olddir newdir Note that the filesystem mount options maintained by the kernel will remain the same as those on the original mount point. The userspace mount options (e.g., _netdev) will not be copied by mount and its necessary to explicitly specify the options on the mount command line. Since util-linux 2.27 mount permits changing the mount options by passing the relevant options along with --bind. For example: mount -o bind,ro foo foo This feature is not supported by the Linux kernel; it is implemented in userspace by an additional mount(2) remounting system call. This solution is not atomic. The alternative (classic) way to create a read-only bind mount is to use the remount operation, for example: mount --bind olddir newdir mount -o remount,bind,ro olddir newdir Note that a read-only bind will create a read-only mountpoint (VFS entry), but the original filesystem superblock will still be writable, meaning that the olddir will be writable, but the newdir will be read-only. Its also possible to change nosuid, nodev, noexec, noatime, nodiratime, relatime and nosymfollow VFS entry flags via a "remount,bind" operation. The other flags (for example filesystem-specific flags) are silently ignored. The classic mount(2) system call does not allow to change mount options recursively (for example with -o rbind,ro). The recursive semantic is possible with a new mount_setattr(2) kernel system call and its supported since libmount from util-linux v2.39 by a new experimental "recursive" option argument (e.g. -o rbind,ro=recursive). For more details see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS section. Since util-linux 2.31, mount ignores the bind flag from /etc/fstab on a remount operation (if -o remount is specified on command line). This is necessary to fully control mount options on remount by command line. In previous versions the bind flag has been always applied and it was impossible to re-define mount options without interaction with the bind semantic. This mount behavior does not affect situations when "remount,bind" is specified in the /etc/fstab file. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink. This feature is usable (only) with the new kernel mount API where bind mount over symlinks is supported. The move operation Move a mounted tree to another place (atomically). The call is: mount --move olddir newdir This will cause the contents which previously appeared under olddir to now be accessible under newdir. The physical location of the files is not changed. Note that olddir has to be a mountpoint. Note also that moving a mount residing under a shared mount is invalid and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current propagation flags. Shared subtree operations Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, private, slave or unbindable. A shared mount provides the ability to create mirrors of that mount such that mounts and unmounts within any of the mirrors propagate to the other mirror. A slave mount receives propagation from its master, but not vice versa. A private mount carries no propagation abilities. An unbindable mount is a private mount which cannot be cloned through a bind operation. The detailed semantics are documented in Documentation/filesystems/sharedsubtree.txt file in the kernel source tree; see also mount_namespaces(7). Supported operations are: mount --make-shared mountpoint mount --make-slave mountpoint mount --make-private mountpoint mount --make-unbindable mountpoint The following commands allow one to recursively change the type of all the mounts under a given mountpoint. mount --make-rshared mountpoint mount --make-rslave mountpoint mount --make-rprivate mountpoint mount --make-runbindable mountpoint mount does not read fstab(5) when a --make-* operation is requested. All necessary information has to be specified on the command line. Note that the Linux kernel does not allow changing multiple propagation flags with a single mount(2) system call, and the flags cannot be mixed with other mount options and operations. Since util-linux 2.23 the mount command can be used to do more propagation (topology) changes by one mount(8) call and do it also together with other mount operations. The propagation flags are applied by additional mount(2) system calls when the preceding mount operations were successful. Note that this use case is not atomic. It is possible to specify the propagation flags in fstab(5) as mount options (private, slave, shared, unbindable, rprivate, rslave, rshared, runbindable). For example: mount --make-private --make-unbindable /dev/sda1 /foo is the same as: mount /dev/sda1 /foo mount --make-private /foo mount --make-unbindable /foo COMMAND-LINE OPTIONS top The full set of mount options used by an invocation of mount is determined by first extracting the mount options for the filesystem from the fstab table, then applying any options specified by the -o argument, and finally applying a -r or -w option, when present. The mount command does not pass all command-line options to the /sbin/mount.suffix mount helpers. The interface between mount and the mount helpers is described below in the EXTERNAL HELPERS section. Command-line options available for the mount command are: -a, --all Mount all filesystems (of the given types) mentioned in fstab (except for those whose line contains the noauto keyword). The filesystems are mounted following their order in fstab. The mount command compares filesystem source, target (and fs root for bind mount or btrfs) to detect already mounted filesystems. The kernel table with already mounted filesystems is cached during mount --all. This means that all duplicated fstab entries will be mounted. The correct functionality depends on /proc (to detect already mounted filesystems) and on /sys (to evaluate filesystem tags like UUID= or LABEL=). Its strongly recommended to mount /proc and /sys filesystems before mount -a is executed, or keep /proc and /sys at the beginning of fstab. The option --all is possible to use for remount operation too. In this case all filters (-t and -O) are applied to the table of already mounted filesystems. Since version 2.35 it is possible to use the command line option -o to alter mount options from fstab (see also --options-mode). Note that it is a bad practice to use mount -a for fstab checking. The recommended solution is findmnt --verify. -B, --bind Remount a subtree somewhere else (so that its contents are available in both places). See above, under Bind mount operation. -c, --no-canonicalize Dont canonicalize paths. The mount command canonicalizes all paths (from the command line or fstab) by default. The option is designed for mount helpers which call mount -i. It is strongly recommended to not use this command-line option for normal mount operations. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink (see "Bind mount operation" section for more details). Note that mount does not pass this option to the /sbin/mount.type helpers. -F, --fork (Used in conjunction with -a.) Fork off a new incarnation of mount for each device. This will do the mounts on different devices or different NFS servers in parallel. This has the advantage that it is faster; also NFS timeouts proceed in parallel. A disadvantage is that the order of the mount operations is undefined. Thus, you cannot use this option if you want to mount both /usr and /usr/spool. -f, --fake Causes everything to be done except for the mount-related system calls. The --fake option was originally designed to write an entry to /etc/mtab without actually mounting. The /etc/mtab is no longer maintained in userspace, and starting from version 2.39, the mount operation can be a complex chain of operations with dependencies between the syscalls. The --fake option forces libmount to skip all mount source preparation, mount option analysis, and the actual mounting process. The difference between fake and non-fake execution is huge. This is the reason why the --fake option has minimal significance for the current mount(8) implementation and it is maintained mostly for backward compatibility. -i, --internal-only Dont call the /sbin/mount.filesystem helper even if it exists. -L, --label label Mount the partition that has the specified label. -l, --show-labels Add the labels in the mount output. mount must have permission to read the disk device (e.g. be set-user-ID root) for this to work. One can set such a label for ext2, ext3 or ext4 using the e2label(8) utility, or for XFS using xfs_admin(8), or for reiserfs using reiserfstune(8). -M, --move Move a subtree to some other place. See above, the subsection The move operation. -m, --mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. Alias to "-o X-mount.mkdir[=mode]", the default mode is 0755. For more details see X-mount.mkdir below. --map-groups, --map-users inner:_outer_:_count_ Add the specified user/group mapping to an X-mount.idmap map. These options can be given multiple times to build up complete mappings for users and groups. For more details see X-mount.idmap below. --map-users /proc/PID/ns/user Use the specified user namespace for user and group mapping in an id-mapped mount. This is an alias for "-o X-mount.idmap=/proc/PID/ns/user" and cannot be used twice nor together with the inner:_outer_:_count_ option format above. For more details see X-mount.idmap below. -n, --no-mtab Mount without writing in /etc/mtab. This is necessary for example when /etc is on a read-only filesystem. -N, --namespace ns Perform the mount operation in the mount namespace specified by ns. ns is either PID of process running in that namespace or special file representing that namespace. mount switches to the mount namespace when it reads /etc/fstab, writes /etc/mtab: (or writes to _/run/mount) and calls mount(2), otherwise it runs in the original mount namespace. This means that the target namespace does not have to contain any libraries or other requirements necessary to execute the mount(2) call. See mount_namespaces(7) for more information. -O, --test-opts opts Limit the set of filesystems to which the -a option applies. In this regard it is like the -t option except that -O is useless without -a. For example, the command mount -a -O no_netdev mounts all filesystems except those which have the option netdev specified in the options field in the /etc/fstab file. It is different from -t in that each option is matched exactly; a leading no at the beginning of one option does not negate the rest. The -t and -O options are cumulative in effect; that is, the command mount -a -t ext2 -O _netdev mounts all ext2 filesystems with the _netdev option, not all filesystems that are either ext2 or have the _netdev option specified. -o, --options opts Use the specified mount options. The opts argument is a comma-separated list. For example: mount LABEL=mydisk -o noatime,nodev,nosuid Note that the order of the options matters, as the last option wins if there are conflicting ones. The options from the command line also overwrite options from fstab by default. For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections. --onlyonce Forces mount command to check if the filesystem is already mounted. This behavior is the default for --all; otherwise, it depends on the kernel filesystem driver. Some filesystems may be mounted more than once on the same mount point (e.g. tmpfs). --options-mode mode Controls how to combine options from fstab/mtab with options from the command line. mode can be one of ignore, append, prepend or replace. For example, append means that options from fstab are appended to options from the command line. The default value is prepend it means command line options are evaluated after fstab options. Note that the last option wins if there are conflicting ones. --options-source source Source of default options. source is a comma-separated list of fstab, mtab and disable. disable disables fstab and mtab and enables --options-source-force. The default value is fstab,mtab. --options-source-force Use options from fstab/mtab even if both device and dir are specified. -R, --rbind Remount a subtree and all possible submounts somewhere else (so that its contents are available in both places). See above, the subsection Bind mount operation. -r, --read-only Mount the filesystem read-only. A synonym is -o ro. Note that, depending on the filesystem type, state and kernel behavior, the system may still write to the device. For example, ext3 and ext4 will replay the journal if the filesystem is dirty. To prevent this kind of write access, you may want to mount an ext3 or ext4 filesystem with the ro,noload mount options or set the block device itself to read-only mode, see the blockdev(8) command. -s Tolerate sloppy mount options rather than failing. This will ignore mount options not supported by a filesystem type. Not all filesystems support this option. Currently its supported by the mount.nfs mount helper only. --source device If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount source. --target directory If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount target. --target-prefix directory Prepend the specified directory to all mount targets. This option can be used to follow fstab, but mount operations are done in another place, for example: mount --all --target-prefix /chroot -o X-mount.mkdir mounts all from system fstab to /chroot, all missing mountpoint are created (due to X-mount.mkdir). See also --fstab to use an alternative fstab. -T, --fstab path Specifies an alternative fstab file. If path is a directory, then the files in the directory are sorted by strverscmp(3); files that start with "." or without an .fstab extension are ignored. The option can be specified more than once. This option is mostly designed for initramfs or chroot scripts where additional configuration is specified beyond standard system configuration. Note that mount does not pass the option --fstab to the /sbin/mount.type helpers, meaning that the alternative fstab files will be invisible for the helpers. This is no problem for normal mounts, but user (non-root) mounts always require fstab to verify the users rights. -t, --types fstype The argument following the -t is used to indicate the filesystem type. The filesystem types which are currently supported depend on the running kernel. See /proc/filesystems and /lib/modules/$(uname -r)/kernel/fs for a complete list of the filesystems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs. The programs mount and umount(8) support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For example 'fuse.sshfs'. Its recommended to use subtype notation rather than add any prefix to the mount source (for example 'sshfs#example.com' is deprecated). If no -t option is given, or if the auto type is specified, mount will try to guess the desired type. mount uses the libblkid(3) library for guessing the filesystem type; if that does not turn up anything that looks familiar, mount will try to read the file /etc/filesystems, or, if that does not exist, /proc/filesystems. All of the filesystem types listed there will be tried, except for those that are labeled "nodev" (e.g. devpts, proc and nfs). If /etc/filesystems ends in a line with a single *, mount will read /proc/filesystems afterwards. While trying, all filesystem types will be mounted with the mount option silent. The auto type may be useful for user-mounted floppies. Creating a file /etc/filesystems can be useful to change the probe order (e.g., to try vfat before msdos or ext3 before ext2) or if you use a kernel module autoloader. More than one type may be specified in a comma-separated list, for the -t option as well as in an /etc/fstab entry. The list of filesystem types for the -t option can be prefixed with no to specify the filesystem types on which no action should be taken. The prefix no has no effect when specified in an /etc/fstab entry. The prefix no can be meaningful with the -a option. For example, the command mount -a -t nomsdos,smbfs mounts all filesystems except those of type msdos and smbfs. For most types all the mount program has to do is issue a simple mount(2) system call, and no detailed knowledge of the filesystem type is required. For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems have a separate mount program. In order to make it possible to treat all types in a uniform way, mount will execute the program /sbin/mount.type (if that exists) when called with type type. Since different versions of the smbmount program have different calling conventions, /sbin/mount.smbfs may have to be a shell script that sets up the desired call. -U, --uuid uuid Mount the partition that has the specified uuid. -v, --verbose Verbose mode. -w, --rw, --read-write Mount the filesystem read/write. Read-write is the kernel default and the mount default is to try read-only if the previous mount(2) syscall with read-write flags on write-protected devices failed. A synonym is -o rw. Note that specifying -w on the command line forces mount to never try read-only mount on write-protected devices or already mounted read-only filesystems. -h, --help Display help text and exit. -V, --version Print version and exit. FILESYSTEM-INDEPENDENT MOUNT OPTIONS top Some of these options are only useful when they appear in the /etc/fstab file. Some of these options could be enabled or disabled by default in the system kernel. To check the current setting see the options in /proc/mounts. Note that filesystems also have per-filesystem specific default mount options (see for example tune2fs -l output for extN filesystems). The options nosuid, noexec, nodiratime, relatime, noatime, strictatime, and nosymfollow are interpreted only by the abstract VFS kernel layer and applied to the mountpoint node rather than to the filesystem itself. Try: findmnt -o TARGET,VFS-OPTIONS,FS-OPTIONS to get a complete overview of filesystems and VFS options. The read-only setting (ro or rw) is interpreted by VFS and the filesystem and depends on how the option is specified on the mount(8) command line. The default is to interpret it on the filesystem level. The operation "-o bind,remount,ro" is applied only to the VFS mountpoint, and operation "-o remount,ro" is applied to VFS and filesystem superblock. This semantic allows create a read-only mountpoint but keeps the filesystem writable from another mountpoint. Since v2.39 libmount can use a new kernel mount interface to set the VFS options recursive. For backward compatibility, this feature is not enabled by default, although recursive operation (e.g. rbind) has been requested. The new option argument "recursive" could be specified, for example: mount -orbind,ro=recursive,noexec=recursive,nosuid /foo /bar recursively binds filesystems from /foo to /bar, /bar, and all submounts will be read-only and noexec, but only /bar itself will be "nosuid". The "recursive" optional argument for VFS mount options is an EXPERIMENTAL feature. The following options apply to any filesystem that is being mounted (but not every filesystem actually honors them - e.g., the sync option today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs): async All I/O to the filesystem should be done asynchronously. (See also the sync option.) atime Do not use the noatime feature, so the inode access time is controlled by kernel defaults. See also the descriptions of the relatime and strictatime mount options. noatime Do not update inode access times on this filesystem (e.g. for faster access on the news spool to speed up news servers). This works for all inode types (directories too), so it implies nodiratime. auto Can be mounted with the -a option. noauto Can only be mounted explicitly (i.e., the -a option will not cause the filesystem to be mounted). context=context, fscontext=context, defcontext=context, and rootcontext=context The context= option is useful when mounting filesystems that do not support extended attributes, such as a floppy or hard disk formatted with VFAT, or systems that are not normally running under SELinux, such as an ext3 or ext4 formatted disk from a non-SELinux workstation. You can also use context= on filesystems you do not trust, such as a floppy. It also helps in compatibility with xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where xattrs are supported, you can save time not having to label every file by assigning the entire disk one security context. A commonly used option for removable media is context="system_u:object_r:removable_t. The fscontext= option works for all filesystems, regardless of their xattr support. The fscontext option sets the overarching filesystem label to a specific security context. This filesystem label is separate from the individual labels on the files. It represents the entire filesystem for certain kinds of permission checks, such as during mount or file creation. Individual file labels are still obtained from the xattrs on the files themselves. The context option actually sets the aggregate context that fscontext provides, in addition to supplying the same label for individual files. You can set the default security context for unlabeled files using defcontext= option. This overrides the value set for unlabeled files in the policy and requires a filesystem that supports xattr labeling. The rootcontext= option allows you to explicitly label the root inode of a FS being mounted before that FS or inode becomes visible to userspace. This was found to be useful for things like stateless Linux. The special value @target can be used to assign the current context of the target mountpoint location. Note that the kernel rejects any remount request that includes the context option, even when unchanged from the current context. Warning: the context value might contain commas, in which case the value has to be properly quoted, otherwise mount will interpret the comma as a separator between mount options. Dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t tmpfs none /mnt -o \ 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec' For more details, see selinux(8). defaults Use the default options: rw, suid, dev, exec, auto, nouser, and async. Note that the real set of all default mount options depends on the kernel and filesystem type. See the beginning of this section for more details. dev Interpret character or block special devices on the filesystem. nodev Do not interpret character or block special devices on the filesystem. diratime Update directory inode access times on this filesystem. This is the default. (This option is ignored when noatime is set.) nodiratime Do not update directory inode access times on this filesystem. (This option is implied when noatime is set.) dirsync All directory updates within the filesystem should be done synchronously. This affects the following system calls: creat(2), link(2), unlink(2), symlink(2), mkdir(2), rmdir(2), mknod(2) and rename(2). exec Permit execution of binaries and other executable files. noexec Do not permit direct execution of any binaries on the mounted filesystem. group Allow an ordinary user to mount the filesystem if one of that users groups matches the group of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line group,dev,suid). iversion Every time the inode is modified, the i_version field will be incremented. noiversion Do not increment the i_version inode field. mand Allow mandatory locks on this filesystem. See fcntl(2). This option was deprecated in Linux 5.15. nomand Do not allow mandatory locks on this filesystem. _netdev The filesystem resides on a device that requires network access (used to prevent the system from attempting to mount these filesystems until the network has been enabled on the system). nofail Do not report errors for this device if it does not exist. relatime Update inode access times relative to modify or change time. Access time is only updated if the previous access time was earlier than or equal to the current modify or change time. (Similar to noatime, but it doesnt break mutt(1) or other applications that need to know if a file has been read since the last time it was modified.) Since Linux 2.6.30, the kernel defaults to the behavior provided by this option (unless noatime was specified), and the strictatime option is required to obtain traditional semantics. In addition, since Linux 2.6.30, the files last access time is always updated if it is more than 1 day old. norelatime Do not use the relatime feature. See also the strictatime mount option. strictatime Allows to explicitly request full atime updates. This makes it possible for the kernel to default to relatime or noatime but still allow userspace to override it. For more details about the default system mount options see /proc/mounts. nostrictatime Use the kernels default behavior for inode access time updates. lazytime Only update times (atime, mtime, ctime) on the in-memory version of the file inode. This mount option significantly reduces writes to the inode table for workloads that perform frequent random writes to preallocated files. The on-disk timestamps are updated only when: the inode needs to be updated for some change unrelated to file timestamps the application employs fsync(2), syncfs(2), or sync(2) an undeleted inode is evicted from memory more than 24 hours have passed since the inode was written to disk. nolazytime Do not use the lazytime feature. suid Honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. nosuid Do not honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. In addition, SELinux domain transitions require permission nosuid_transition, which in turn needs also policy capability nnp_nosuid_transition. silent Turn on the silent flag. loud Turn off the silent flag. owner Allow an ordinary user to mount the filesystem if that user is the owner of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line owner,dev,suid). remount Attempt to remount an already-mounted filesystem. This is commonly used to change the mount flags for a filesystem, especially to make a readonly filesystem writable. It does not change device or mount point. The remount operation together with the bind flag has special semantics. See above, the subsection Bind mount operation. The default kernel behavior for VFS mount flags (nodev,nosuid,noexec,ro) is to reset all unspecified flags on remount. Thats why mount(8) tries to keep the current setting according to fstab or /proc/self/mountinfo. This default behavior is possible to change by --options-mode. The recursive change of the mount flags (supported since v2.39 on systems with mount_setattr(2) syscall), for example, mount -o remount,ro=recursive, do not use "reset-unspecified" behavior, and it works as a simple add/remove operation and unspecified flags are not modified. The remount functionality follows the standard way the mount command works with options from fstab. This means that mount does not read fstab (or mtab) only when both device and dir are specified. mount -o remount,rw /dev/foo /dir After this call all old mount options are replaced and arbitrary stuff from fstab (or mtab) is ignored, except the loop= option which is internally generated and maintained by the mount command. mount -o remount,rw /dir After this call, mount reads fstab and merges these options with the options from the command line (-o). If no mountpoint is found in fstab, then it defaults to mount options from /proc/self/mountinfo. mount allows the use of --all to remount all already mounted filesystems which match a specified filter (-O and -t). For example: mount --all -o remount,ro -t vfat remounts all already mounted vfat filesystems in read-only mode. Each of the filesystems is remounted by mount -o remount,ro /dir semantic. This means the mount command reads fstab or mtab and merges these options with the options from the command line. ro Mount the filesystem read-only. rw Mount the filesystem read-write. sync All I/O to the filesystem should be done synchronously. In the case of media with a limited number of write cycles (e.g. some flash drives), sync may cause life-cycle shortening. user Allow an ordinary user to mount the filesystem. The name of the mounting user is written to the mtab file (or to the private libmount file in /run/mount on systems without a regular mtab) so that this same user can unmount the filesystem again. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line user,exec,dev,suid). nouser Forbid an ordinary user to mount the filesystem. This is the default; it does not imply any other options. users Allow any user to mount and to unmount the filesystem, even when some other ordinary user mounted it. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line users,exec,dev,suid). X-* All options prefixed with "X-" are interpreted as comments or as userspace application-specific options. These options are not stored in user space (e.g., mtab file), nor sent to the mount.type helpers nor to the mount(2) system call. The suggested format is X-appname.option. x-* The same as X-* options, but stored permanently in user space. This means the options are also available for umount(8) or other operations. Note that maintaining mount options in user space is tricky, because its necessary use libmount-based tools and there is no guarantee that the options will be always available (for example after a move mount operation or in unshared namespace). Note that before util-linux v2.30 the x-* options have not been maintained by libmount and stored in user space (functionality was the same as for X-* now), but due to the growing number of use-cases (in initrd, systemd etc.) the functionality has been extended to keep existing fstab configurations usable without a change. X-mount.auto-fstypes=list Specifies allowed or forbidden filesystem types for automatic filesystem detection. The list is a comma-separated list of the filesystem names. The automatic filesystem detection is triggered by the "auto" filesystem type or when the filesystem type is not specified. Thy list follows how mount evaluates type patterns (see -t for more details). Only specified filesystem types are allowed, or all specified types are forbidden if the list is prefixed by "no". For example, X-mount.auto-fstypes="ext4,btrfs" accepts only ext4 and btrfs, and X-mount.auto-fstypes="novfat,xfs" accepts all filesystems except vfat and xfs. Note that comma is used as a separator between mount options, it means that auto-fstypes values have to be properly quoted, dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t auto -oX-mount.auto-fstypes="noext2,ext3"' /dev/sdc1 /mnt/test X-mount.mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. The optional argument mode specifies the filesystem access mode used for mkdir(2) in octal notation. The default mode is 0755. This functionality is supported only for root users or when mount is executed without suid permissions. The option is also supported as x-mount.mkdir, but this notation is deprecated since v2.30. See also --mkdir command line option. X-mount.subdir=directory Allow mounting sub-directory from a filesystem instead of the root directory. For now, this feature is implemented by temporary filesystem root directory mount in unshared namespace and then bind the sub-directory to the final mount point and umount the root of the filesystem. The sub-directory mount shows up atomically for the rest of the system although it is implemented by multiple mount(2) syscalls. Note that this feature will not work in session with an unshared private mount namespace (after unshare --mount) on old kernels or with mount(8) without support for file-descriptors-based mount kernel API. In this case, you need unshare --mount --propagation shared. This feature is EXPERIMENTAL. X-mount.owner=username|UID, X-mount.group=group|GID Set mountpoint's ownership after mounting. Names resolved in the target mount namespace, see -N. X-mount.mode=mode Set mountpoint's mode after mounting. X-mount.idmap=id-type:id-mount:id-host:id-range [id-type:id-mount:id-host:id-range], X-mount.idmap=file Use this option to create an idmapped mount. An idmapped mount allows to change ownership of all files located under a mount according to the ID-mapping associated with a user namespace. The ownership change is tied to the lifetime and localized to the relevant mount. The relevant ID-mapping can be specified in two ways: A user can specify the ID-mapping directly. The ID-mapping must be specified using the syntax id-type:id-mount:id-host:id-range. Specifying u as the id-type prefix creates a UID-mapping, g creates a GID-mapping and omitting id-type or specifying b creates both a UID- and GID-mapping. The id-mount parameter indicates the starting ID in the new mount. The id-host parameter indicates the starting ID in the filesystem. The id-range parameter indicates how many IDs are to be mapped. It is possible to specify multiple ID-mappings. The individual ID-mappings must be separated by spaces. For example, the ID-mapping X-mount.idmap=u:1000:0:1 g:1001:1:2 5000:1000:2 creates an idmapped mount where UID 0 is mapped to UID 1000, GID 1 is mapped to GUID 1001, GID 2 is mapped to GID 1002, UID and GID 1000 are mapped to 5000, and UID and GID 1001 are mapped to 5001 in the mount. When an ID-mapping is specified directly a new user namespace will be allocated with the requested ID-mapping. The newly created user namespace will be attached to the mount. A user can specify a user namespace file. The user namespace will then be attached to the mount and the ID-mapping of the user namespace will become the ID-mapping of the mount. For example, X-mount.idmap=/proc/PID/ns/user will attach the user namespace of the process PID to the mount. nosymfollow Do not follow symlinks when resolving paths. Symlinks can still be created, and readlink(1), readlink(2), realpath(1), and realpath(3) all still work properly. FILESYSTEM-SPECIFIC MOUNT OPTIONS top This section lists options that are specific to particular filesystems. Where possible, you should first consult filesystem-specific manual pages for details. Some of those pages are listed in the following table. Filesystem(s) Manual page btrfs btrfs(5) cifs mount.cifs(8) ext2, ext3, ext4 ext4(5) fuse fuse(8) nfs nfs(5) tmpfs tmpfs(5) xfs xfs(5) Note that some of the pages listed above might be available only after you install the respective userland tools. The following options apply only to certain filesystems. We sort them by filesystem. All options follow the -o flag. What options are supported depends a bit on the running kernel. Further information may be available in filesystem-specific files in the kernel source subdirectory Documentation/filesystems. Mount options for adfs uid=value and gid=value Set the owner and group of the files in the filesystem (default: uid=gid=0). ownmask=value and othmask=value Set the permission mask for ADFS 'owner' permissions and 'other' permissions, respectively (default: 0700 and 0077, respectively). See also /usr/src/linux/Documentation/filesystems/adfs.rst. Mount options for affs uid=value and gid=value Set the owner and group of the root of the filesystem (default: uid=gid=0, but with option uid or gid without specified value, the UID and GID of the current process are taken). setuid=value and setgid=value Set the owner and group of all files. mode=value Set the mode of all files to value & 0777 disregarding the original permissions. Add search permission to directories that have read permission. The value is given in octal. protect Do not allow any changes to the protection bits on the filesystem. usemp Set UID and GID of the root of the filesystem to the UID and GID of the mount point upon the first sync or umount, and then clear this option. Strange... verbose Print an informational message for each successful mount. prefix=string Prefix used before volume name, when following a link. volume=string Prefix (of length at most 30) used before '/' when following a symbolic link. reserved=value (Default: 2.) Number of unused blocks at the start of the device. root=value Give explicitly the location of the root block. bs=value Give blocksize. Allowed values are 512, 1024, 2048, 4096. grpquota|noquota|quota|usrquota These options are accepted but ignored. (However, quota utilities may react to such strings in /etc/fstab.) Mount options for debugfs The debugfs filesystem is a pseudo filesystem, traditionally mounted on /sys/kernel/debug. As of kernel version 3.4, debugfs has the following options: uid=n, gid=n Set the owner and group of the mountpoint. mode=value Sets the mode of the mountpoint. Mount options for devpts The devpts filesystem is a pseudo filesystem, traditionally mounted on /dev/pts. In order to acquire a pseudo terminal, a process opens /dev/ptmx; the number of the pseudo terminal is then made available to the process and the pseudo terminal slave can be accessed as /dev/pts/<number>. uid=value and gid=value This sets the owner or the group of newly created pseudo terminals to the specified values. When nothing is specified, they will be set to the UID and GID of the creating process. For example, if there is a tty group with GID 5, then gid=5 will cause newly created pseudo terminals to belong to the tty group. mode=value Set the mode of newly created pseudo terminals to the specified value. The default is 0600. A value of mode=620 and gid=5 makes "mesg y" the default on newly created pseudo terminals. newinstance Create a private instance of the devpts filesystem, such that indices of pseudo terminals allocated in this new instance are independent of indices created in other instances of devpts. All mounts of devpts without this newinstance option share the same set of pseudo terminal indices (i.e., legacy mode). Each mount of devpts with the newinstance option has a private set of pseudo terminal indices. This option is mainly used to support containers in the Linux kernel. It is implemented in Linux kernel versions starting with 2.6.29. Further, this mount option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. To use this option effectively, /dev/ptmx must be a symbolic link to pts/ptmx. See Documentation/filesystems/devpts.txt in the Linux kernel source tree for details. ptmxmode=value Set the mode for the new ptmx device node in the devpts filesystem. With the support for multiple instances of devpts (see newinstance option above), each instance has a private ptmx node in the root of the devpts filesystem (typically /dev/pts/ptmx). For compatibility with older versions of the kernel, the default mode of the new ptmx node is 0000. ptmxmode=value specifies a more useful mode for the ptmx node and is highly recommended when the newinstance option is specified. This option is only implemented in Linux kernel versions starting with 2.6.29. Further, this option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. Mount options for fat (Note: fat is not a separate filesystem, but a common part of the msdos, umsdos and vfat filesystems.) blocksize={512|1024|2048} Set blocksize (default 512). This option is obsolete. uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. dmask=value Set the umask applied to directories only. The default is the umask of the current process. The value is given in octal. fmask=value Set the umask applied to regular files only. The default is the umask of the current process. The value is given in octal. allow_utime=value This option controls the permission check of mtime/atime. 20 If current process is in group of files group ID, you can change timestamp. 2 Other users can change timestamp. The default is set from 'dmask' option. (If the directory is writable, utime(2) is also allowed. I.e. ~dmask & 022) Normally utime(2) checks that the current process is owner of the file, or that it has the CAP_FOWNER capability. But FAT filesystems dont have UID/GID on disk, so the normal check is too inflexible. With this option you can relax it. check=value Three different levels of pickiness can be chosen: r[elaxed] Upper and lower case are accepted and equivalent, long name parts are truncated (e.g. verylongname.foobar becomes verylong.foo), leading and embedded spaces are accepted in each name part (name and extension). n[ormal] Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are rejected. This is the default. s[trict] Like "normal", but names that contain long parts or special characters that are sometimes used on Linux but are not accepted by MS-DOS (+, =, etc.) are rejected. codepage=value Sets the codepage for converting to shortname characters on FAT and VFAT filesystems. By default, codepage 437 is used. conv=mode This option is obsolete and may fail or be ignored. cvf_format=module Forces the driver to use the CVF (Compressed Volume File) module cvf_module instead of auto-detection. If the kernel supports kmod, the cvf_format=xxx option also controls on-demand CVF module loading. This option is obsolete. cvf_option=option Option passed to the CVF module. This option is obsolete. debug Turn on the debug flag. A version string and a list of filesystem parameters will be printed (these data are also printed if the parameters appear to be inconsistent). discard If set, causes discard/TRIM commands to be issued to the block device when blocks are freed. This is useful for SSD devices and sparse/thinly-provisioned LUNs. dos1xfloppy If set, use a fallback default BIOS Parameter Block configuration, determined by backing device size. These static parameters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images. errors={panic|continue|remount-ro} Specify FAT behavior on critical errors: panic, continue without doing anything, or remount the partition in read-only mode (default behavior). fat={12|16|32} Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT type detection routine. Use with caution! iocharset=value Character set to use for converting between 8 bit characters and 16 bit Unicode characters. The default is iso8859-1. Long filenames are stored on disk in Unicode format. nfs={stale_rw|nostale_ro} Enable this only if you want to export the FAT filesystem over NFS. stale_rw: This option maintains an index (cache) of directory inodes which is used by the nfs-related code to improve look-ups. Full file operations (read/write) over NFS are supported but with cache eviction at NFS server, this could result in spurious ESTALE errors. nostale_ro: This option bases the inode number and file handle on the on-disk location of a file in the FAT directory entry. This ensures that ESTALE will not be returned after a file is evicted from the inode cache. However, it means that operations such as rename, create and unlink could cause file handles that previously pointed at one file to point at a different file, potentially causing data corruption. For this reason, this option also mounts the filesystem readonly. To maintain backward compatibility, -o nfs is also accepted, defaulting to stale_rw. tz=UTC This option disables the conversion of timestamps between local time (as used by Windows on FAT) and UTC (which Linux uses internally). This is particularly useful when mounting devices (like digital cameras) that are set to UTC in order to avoid the pitfalls of local time. time_offset=minutes Set offset for conversion of timestamps from local time used by FAT to UTC. I.e., minutes will be subtracted from each timestamp to convert it to UTC used internally by Linux. This is useful when the time zone set in the kernel via settimeofday(2) is not the time zone used by the filesystem. Note that this option still does not provide correct time stamps in all cases in presence of DST - time stamps in a different DST setting will be off by one hour. quiet Turn on the quiet flag. Attempts to chown or chmod files do not return errors, although they fail. Use with caution! rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO of the directory will just be ignored, and is used only by applications as a flag (e.g. its set for the customized folder). If you want to use ATTR_RO as read-only flag even for the directory, set this option. showexec If set, the execute permission bits of the file will be allowed only if the extension part of the name is .EXE, .COM, or .BAT. Not set by default. sys_immutable If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux. Not set by default. flush If set, the filesystem will try to flush to disk more early than normal. Not set by default. usefree Use the "free clusters" value stored on FSINFO. Itll be used to determine number of free clusters without scanning disk. But its not used by default, because recent Windows dont update it correctly in some case. If you are sure the "free clusters" on FSINFO is correct, by this option you can avoid scanning disk. dots, nodots, dotsOK=[yes|no] Various misguided attempts to force Unix or DOS conventions onto a FAT filesystem. Mount options for hfs creator=cccc, type=cccc Set the creator/type values as shown by the MacOS finder used for creating new files. Default values: '????'. uid=n, gid=n Set the owner and group of all files. (Default: the UID and GID of the current process.) dir_umask=n, file_umask=n, umask=n Set the umask used for all directories, all regular files, or all files and directories. Defaults to the umask of the current process. session=n Select the CDROM session to mount. Defaults to leaving that decision to the CDROM driver. This option will fail with anything but a CDROM as underlying device. part=n Select partition number n from the device. Only makes sense for CDROMs. Defaults to not parsing the partition table at all. quiet Dont complain about invalid mount options. Mount options for hpfs uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. case={lower|asis} Convert all files names to lower case, or leave them. (Default: case=lower.) conv=mode This option is obsolete and may fail or being ignored. nocheck Do not abort mounting when certain consistency checks fail. Mount options for iso9660 ISO 9660 is a standard describing a filesystem structure to be used on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the udf filesystem.) Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like restrictions on filename length), and in addition all characters are in upper case. Also there is no field for file ownership, protection, number of links, provision for block/character devices, etc. Rock Ridge is an extension to iso9660 that provides all of these UNIX-like features. Basically there are extensions to each directory record that supply all of the additional information, and when Rock Ridge is in use, the filesystem is indistinguishable from a normal UNIX filesystem (except that it is read-only, of course). norock Disable the use of Rock Ridge extensions, even if available. Cf. map. nojoliet Disable the use of Microsoft Joliet extensions, even if available. Cf. map. check={r[elaxed]|s[trict]} With check=relaxed, a filename is first converted to lower case before doing the lookup. This is probably only meaningful together with norock and map=normal. (Default: check=strict.) uid=value and gid=value Give all files in the filesystem the indicated user or group id, possibly overriding the information found in the Rock Ridge extensions. (Default: uid=0,gid=0.) map={n[ormal]|o[ff]|a[corn]} For non-Rock Ridge volumes, normal name translation maps upper to lower case ASCII, drops a trailing ';1', and converts ';' to '.'. With map=off no name translation is done. See norock. (Default: map=normal.) map=acorn is like map=normal but also apply Acorn extensions if present. mode=value For non-Rock Ridge volumes, give all files the indicated mode. (Default: read and execute permission for everybody.) Octal mode values require a leading 0. unhide Also show hidden and associated files. (If the ordinary files and the associated or hidden files have the same filenames, this may make the ordinary files inaccessible.) block={512|1024|2048} Set the block size to the indicated value. (Default: block=1024.) conv=mode This option is obsolete and may fail or being ignored. cruft If the high byte of the file length contains other garbage, set this mount option to ignore the high order bits of the file length. This implies that a file cannot be larger than 16 MB. session=x Select number of session on a multisession CD. sbsector=xxx Session begins from sector xxx. The following options are the same as for vfat and specifying them only makes sense when using discs encoded using Microsofts Joliet extensions. iocharset=value Character set to use for converting 16 bit Unicode characters on CD to 8 bit characters. The default is iso8859-1. utf8 Convert 16 bit Unicode characters on CD to UTF-8. Mount options for jfs iocharset=name Character set to use for converting from Unicode to ASCII. The default is to do no conversion. Use iocharset=utf8 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in the kernel .config file. resize=value Resize the volume to value blocks. JFS only supports growing a volume, not shrinking it. This option is only valid during a remount, when the volume is mounted read-write. The resize keyword with no value will grow the volume to the full size of the partition. nointegrity Do not write to the journal. The primary use of this option is to allow for higher performance when restoring a volume from backup media. The integrity of the volume is not guaranteed if the system abnormally ends. integrity Default. Commit metadata changes to the journal. Use this option to remount a volume where the nointegrity option was previously specified in order to restore normal behavior. errors={continue|remount-ro|panic} Define the behavior when an error is encountered. (Either ignore errors and just mark the filesystem erroneous and continue, or remount the filesystem read-only, or panic and halt the system.) noquota|quota|usrquota|grpquota These options are accepted but ignored. Mount options for msdos See mount options for fat. If the msdos filesystem detects an inconsistency, it reports an error and sets the file system read-only. The filesystem can be made writable again by remounting it. Mount options for ncpfs Just like nfs, the ncpfs implementation expects a binary argument (a struct ncp_mount_data) to the mount(2) system call. This argument is constructed by ncpmount(8) and the current version of mount (2.12) does not know anything about ncpfs. Mount options for ntfs iocharset=name Character set to use when returning file names. Unlike VFAT, NTFS suppresses names that contain nonconvertible characters. Deprecated. nls=name New name for the option earlier called iocharset. utf8 Use UTF-8 for converting file names. uni_xlate={0|1|2} For 0 (or 'no' or 'false'), do not use escape sequences for unknown Unicode characters. For 1 (or 'yes' or 'true') or 2, use vfat-style 4-byte escape sequences starting with ":". Here 2 gives a little-endian encoding and 1 a byteswapped bigendian encoding. posix=[0|1] If enabled (posix=1), the filesystem distinguishes between upper and lower case. The 8.3 alias names are presented as hard links instead of being suppressed. This option is obsolete. uid=value, gid=value and umask=value Set the file permission on the filesystem. The umask value is given in octal. By default, the files are owned by root and not readable by somebody else. Mount options for overlay Since Linux 3.18 the overlay pseudo filesystem implements a union mount for other filesystems. An overlay filesystem combines two filesystems - an upper filesystem and a lower filesystem. When a name exists in both filesystems, the object in the upper filesystem is visible while the object in the lower filesystem is either hidden or, in the case of directories, merged with the upper object. The lower filesystem can be any filesystem supported by Linux and does not need to be writable. The lower filesystem can even be another overlayfs. The upper filesystem will normally be writable and if it is it must support the creation of trusted.* extended attributes, and must provide a valid d_type in readdir responses, so NFS is not suitable. A read-only overlay of two read-only filesystems may use any filesystem type. The options lowerdir and upperdir are combined into a merged directory by using: mount -t overlay overlay \ -olowerdir=/lower,upperdir=/upper,workdir=/work /merged lowerdir=directory Any filesystem, does not need to be on a writable filesystem. upperdir=directory The upperdir is normally on a writable filesystem. workdir=directory The workdir needs to be an empty directory on the same filesystem as upperdir. userxattr Use the "user.overlay." xattr namespace instead of "trusted.overlay.". This is useful for unprivileged mounting of overlayfs. redirect_dir={on|off|follow|nofollow} If the redirect_dir feature is enabled, then the directory will be copied up (but not the contents). Then the "{trusted|user}.overlay.redirect" extended attribute is set to the path of the original location from the root of the overlay. Finally the directory is moved to the new location. on Redirects are enabled. off Redirects are not created and only followed if "redirect_always_follow" feature is enabled in the kernel/module config. follow Redirects are not created, but followed. nofollow Redirects are not created and not followed (equivalent to "redirect_dir=off" if "redirect_always_follow" feature is not enabled). index={on|off} Inode index. If this feature is disabled and a file with multiple hard links is copied up, then this will "break" the link. Changes will not be propagated to other names referring to the same inode. uuid={on|off} Can be used to replace UUID of the underlying filesystem in file handles with null, and effectively disable UUID checks. This can be useful in case the underlying disk is copied and the UUID of this copy is changed. This is only applicable if all lower/upper/work directories are on the same filesystem, otherwise it will fallback to normal behaviour. nfs_export={on|off} When the underlying filesystems supports NFS export and the "nfs_export" feature is enabled, an overlay filesystem may be exported to NFS. With the "nfs_export" feature, on copy_up of any lower object, an index entry is created under the index directory. The index entry name is the hexadecimal representation of the copy up origin file handle. For a non-directory object, the index entry is a hard link to the upper inode. For a directory object, the index entry has an extended attribute "{trusted|user}.overlay.upper" with an encoded file handle of the upper directory inode. When encoding a file handle from an overlay filesystem object, the following rules apply For a non-upper object, encode a lower file handle from lower inode For an indexed object, encode a lower file handle from copy_up origin For a pure-upper object and for an existing non-indexed upper object, encode an upper file handle from upper inode The encoded overlay file handle includes Header including path type information (e.g. lower/upper) UUID of the underlying filesystem Underlying filesystem encoding of underlying inode This encoding format is identical to the encoding format of file handles that are stored in extended attribute "{trusted|user}.overlay.origin". When decoding an overlay file handle, the following steps are followed Find underlying layer by UUID and path type information. Decode the underlying filesystem file handle to underlying dentry. For a lower file handle, lookup the handle in index directory by name. If a whiteout is found in index, return ESTALE. This represents an overlay object that was deleted after its file handle was encoded. For a non-directory, instantiate a disconnected overlay dentry from the decoded underlying dentry, the path type and index inode, if found. For a directory, use the connected underlying decoded dentry, path type and index, to lookup a connected overlay dentry. Decoding a non-directory file handle may return a disconnected dentry. copy_up of that disconnected dentry will create an upper index entry with no upper alias. When overlay filesystem has multiple lower layers, a middle layer directory may have a "redirect" to lower directory. Because middle layer "redirects" are not indexed, a lower file handle that was encoded from the "redirect" origin directory, cannot be used to find the middle or upper layer directory. Similarly, a lower file handle that was encoded from a descendant of the "redirect" origin directory, cannot be used to reconstruct a connected overlay path. To mitigate the cases of directories that cannot be decoded from a lower file handle, these directories are copied up on encode and encoded as an upper file handle. On an overlay filesystem with no upper layer this mitigation cannot be used NFS export in this setup requires turning off redirect follow (e.g. "redirect_dir=nofollow"). The overlay filesystem does not support non-directory connectable file handles, so exporting with the subtree_check exportfs configuration will cause failures to lookup files over NFS. When the NFS export feature is enabled, all directory index entries are verified on mount time to check that upper file handles are not stale. This verification may cause significant overhead in some cases. Note: the mount options index=off,nfs_export=on are conflicting for a read-write mount and will result in an error. xino={on|off|auto} The "xino" feature composes a unique object identifier from the real object st_ino and an underlying fsid index. The "xino" feature uses the high inode number bits for fsid, because the underlying filesystems rarely use the high inode number bits. In case the underlying inode number does overflow into the high xino bits, overlay filesystem will fall back to the non xino behavior for that inode. For a detailed description of the effect of this option please refer to https://docs.kernel.org/filesystems/overlayfs.html metacopy={on|off} When metadata only copy up feature is enabled, overlayfs will only copy up metadata (as opposed to whole file), when a metadata specific operation like chown/chmod is performed. Full file will be copied up later when file is opened for WRITE operation. In other words, this is delayed data copy up operation and data is copied up when there is a need to actually modify data. volatile Volatile mounts are not guaranteed to survive a crash. It is strongly recommended that volatile mounts are only used if data written to the overlay can be recreated without significant effort. The advantage of mounting with the "volatile" option is that all forms of sync calls to the upper filesystem are omitted. In order to avoid a giving a false sense of safety, the syncfs (and fsync) semantics of volatile mounts are slightly different than that of the rest of VFS. If any writeback error occurs on the upperdirs filesystem after a volatile mount takes place, all sync functions will return an error. Once this condition is reached, the filesystem will not recover, and every subsequent sync call will return an error, even if the upperdir has not experience a new error since the last sync call. When overlay is mounted with "volatile" option, the directory "$workdir/work/incompat/volatile" is created. During next mount, overlay checks for this directory and refuses to mount if present. This is a strong indicator that user should throw away upper and work directories and create fresh one. In very limited cases where the user knows that the system has not crashed and contents of upperdir are intact, The "volatile" directory can be removed. Mount options for reiserfs Reiserfs is a journaling filesystem. conv Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem, using the 3.6 format for newly created objects. This filesystem will no longer be compatible with reiserfs 3.5 tools. hash={rupasov|tea|r5|detect} Choose which hash function reiserfs will use to find files within directories. rupasov A hash invented by Yury Yu. Rupasov. It is fast and preserves locality, mapping lexicographically close file names to close hash values. This option should not be used, as it causes a high probability of hash collisions. tea A Davis-Meyer function implemented by Jeremy Fitzhardinge. It uses hash permuting bits in the name. It gets high randomness and, therefore, low probability of hash collisions at some CPU cost. This may be used if EHASHCOLLISION errors are experienced with the r5 hash. r5 A modified version of the rupasov hash. It is used by default and is the best choice unless the filesystem has huge directories and unusual file-name patterns. detect Instructs mount to detect which hash function is in use by examining the filesystem being mounted, and to write this information into the reiserfs superblock. This is only useful on the first mount of an old format filesystem. hashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. no_unhashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. noborder Disable the border allocator algorithm invented by Yury Yu. Rupasov. This may provide performance improvements in some situations. nolog Disable journaling. This will provide slight performance improvements in some situations at the cost of losing reiserfss fast recovery from crashes. Even with this option turned on, reiserfs still performs all journaling operations, save for actual writes into its journaling area. Implementation of nolog is a work in progress. notail By default, reiserfs stores small files and 'file tails' directly into its tree. This confuses some utilities such as lilo(8). This option is used to disable packing of files into the tree. replayonly Replay the transactions which are in the journal, but do not actually mount the filesystem. Mainly used by reiserfsck. resize=number A remount option which permits online expansion of reiserfs partitions. Instructs reiserfs to assume that the device has number blocks. This option is designed for use with devices which are under logical volume management (LVM). There is a special resizer utility which can be obtained from ftp://ftp.namesys.com/pub/reiserfsprogs. user_xattr Enable Extended User Attributes. See the attr(1) manual page. acl Enable POSIX Access Control Lists. See the acl(5) manual page. barrier=none / barrier=flush This disables / enables the use of write barriers in the journaling code. barrier=none disables, barrier=flush enables (default). This also requires an IO stack which can support barriers, and if reiserfs gets an error on a barrier write, it will disable barriers again with a warning. Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance penalty. If your disks are battery-backed in one way or another, disabling barriers may safely improve performance. Mount options for ubifs UBIFS is a flash filesystem which works on top of UBI volumes. Note that atime is not supported and is always turned off. The device name may be specified as ubiX_Y UBI device number X, volume number Y ubiY UBI device number 0, volume number Y ubiX:NAME UBI device number X, volume with name NAME ubi:NAME UBI device number 0, volume with name NAME Alternative ! separator may be used instead of :. The following mount options are available: bulk_read Enable bulk-read. VFS read-ahead is disabled because it slows down the filesystem. Bulk-Read is an internal optimization. Some flashes may read faster if the data are read at one go, rather than at several read requests. For example, OneNAND can do "read-while-load" if it reads more than one NAND page. no_bulk_read Do not bulk-read. This is the default. chk_data_crc Check data CRC-32 checksums. This is the default. no_chk_data_crc Do not check data CRC-32 checksums. With this option, the filesystem does not check CRC-32 checksum for data, but it does check it for the internal indexing information. This option only affects reading, not writing. CRC-32 is always calculated when writing the data. compr={none|lzo|zlib} Select the default compressor which is used when new files are written. It is still possible to read compressed files if mounted with the none option. Mount options for udf UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical Storage Technology Association, and is often used for DVD-ROM, frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, however, perfectly usable by itself on disk drives, flash drives and other block devices. See also iso9660. uid= Make all files in the filesystem belong to the given user. uid=forget can be specified independently of (or usually in addition to) uid=<user> and results in UDF not storing uids to the media. In fact the recorded uid is the 32-bit overflow uid -1 as defined by the UDF standard. The value is given as either <user> which is a valid user name or the corresponding decimal user id, or the special string "forget". gid= Make all files in the filesystem belong to the given group. gid=forget can be specified independently of (or usually in addition to) gid=<group> and results in UDF not storing gids to the media. In fact the recorded gid is the 32-bit overflow gid -1 as defined by the UDF standard. The value is given as either <group> which is a valid group name or the corresponding decimal group id, or the special string "forget". umask= Mask out the given permissions from all inodes read from the filesystem. The value is given in octal. mode= If mode= is set the permissions of all non-directory inodes read from the filesystem will be set to the given mode. The value is given in octal. dmode= If dmode= is set the permissions of all directory inodes read from the filesystem will be set to the given dmode. The value is given in octal. bs= Set the block size. Default value prior to kernel version 2.6.30 was 2048. Since 2.6.30 and prior to 4.11 it was logical device block size with fallback to 2048. Since 4.11 it is logical block size with fallback to any valid block size between logical device block size and 4096. For other details see the mkudffs(8) 2.0+ manpage, see the COMPATIBILITY and BLOCK SIZE sections. unhide Show otherwise hidden files. undelete Show deleted files in lists. adinicb Embed data in the inode. (default) noadinicb Dont embed data in the inode. shortad Use short UDF address descriptors. longad Use long UDF address descriptors. (default) nostrict Unset strict conformance. iocharset= Set the NLS character set. This requires kernel compiled with CONFIG_UDF_NLS option. utf8 Set the UTF-8 character set. Mount options for debugging and disaster recovery novrs Ignore the Volume Recognition Sequence and attempt to mount anyway. session= Select the session number for multi-session recorded optical media. (default= last session) anchor= Override standard anchor location. (default= 256) lastblock= Set the last block of the filesystem. Unused historical mount options that may be encountered and should be removed uid=ignore Ignored, use uid=<user> instead. gid=ignore Ignored, use gid=<group> instead. volume= Unimplemented and ignored. partition= Unimplemented and ignored. fileset= Unimplemented and ignored. rootdir= Unimplemented and ignored. Mount options for ufs ufstype=value UFS is a filesystem widely used in different operating systems. The problem are differences among implementations. Features of some implementations are undocumented, so its hard to recognize the type of ufs automatically. Thats why the user must specify the type of ufs by mount option. Possible values are: old Old format of ufs, this is the default, read only. (Dont forget to give the -r option.) 44bsd For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD). ufs2 Used in FreeBSD 5.x supported as read-write. 5xbsd Synonym for ufs2. sun For filesystems created by SunOS or Solaris on Sparc. sunx86 For filesystems created by Solaris on x86. hp For filesystems created by HP-UX, read-only. nextstep For filesystems created by NeXTStep (on NeXT station) (currently read only). nextstep-cd For NextStep CDROMs (block_size == 2048), read-only. openstep For filesystems created by OpenStep (currently read only). The same filesystem type is also used by macOS. onerror=value Set behavior on error: panic If an error is encountered, cause a kernel panic. [lock|umount|repair] These mount options dont do anything at present; when an error is encountered only a console message is printed. Mount options for umsdos See mount options for msdos. The dotsOK option is explicitly killed by umsdos. Mount options for vfat First of all, the mount options for fat are recognized. The dotsOK option is explicitly killed by vfat. Furthermore, there are uni_xlate Translate unhandled Unicode characters to special escaped sequences. This lets you backup and restore filenames that are created with any Unicode characters. Without this option, a '?' is used when no translation is possible. The escape character is ':' because it is otherwise invalid on the vfat filesystem. The escape sequence that gets used, where u is the Unicode character, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12). posix Allow two files with names that only differ in case. This option is obsolete. nonumtail First try to make a short name without sequence number, before trying name~num.ext. utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the console. It can be enabled for the filesystem with this option or disabled with utf8=0, utf8=no or utf8=false. If uni_xlate gets set, UTF8 gets disabled. shortname=mode Defines the behavior for creation and display of filenames which fit into 8.3 characters. If a long name for a file exists, it will always be the preferred one for display. There are four modes: lower Force the short name to lower case upon display; store a long name when the short name is not all upper case. win95 Force the short name to upper case upon display; store a long name when the short name is not all upper case. winnt Display the short name as is; store a long name when the short name is not all lower case or all upper case. mixed Display the short name as is; store a long name when the short name is not all upper case. This mode is the default since Linux 2.6.32. Mount options for usbfs devuid=uid and devgid=gid and devmode=mode Set the owner and group and mode of the device files in the usbfs filesystem (default: uid=gid=0, mode=0644). The mode is given in octal. busuid=uid and busgid=gid and busmode=mode Set the owner and group and mode of the bus directories in the usbfs filesystem (default: uid=gid=0, mode=0555). The mode is given in octal. listuid=uid and listgid=gid and listmode=mode Set the owner and group and mode of the file devices (default: uid=gid=0, mode=0444). The mode is given in octal. DM-VERITY SUPPORT top The device-mapper verity target provides read-only transparent integrity checking of block devices using kernel crypto API. The mount command can open the dm-verity device and do the integrity verification before the device filesystem is mounted. Requires libcryptsetup with in libmount (optionally via dlopen(3)). If libcryptsetup supports extracting the root hash of an already mounted device, existing devices will be automatically reused in case of a match. Mount options for dm-verity: verity.hashdevice=path Path to the hash tree device associated with the source volume to pass to dm-verity. verity.roothash=hex Hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothashfile. verity.roothashfile=path Path to file containing the hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothash. verity.hashoffset=offset If the hash tree device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the tree. verity.fecdevice=path Path to the Forward Error Correction (FEC) device associated with the source volume to pass to dm-verity. Optional. Requires kernel built with CONFIG_DM_VERITY_FEC. verity.fecoffset=offset If the FEC device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the FEC area. Optional. verity.fecroots=value Parity bytes for FEC (default: 2). Optional. verity.roothashsig=path Path to pkcs7(1ssl) signature of root hash hex string. Requires crypt_activate_by_signed_key() from cryptsetup and kernel built with CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG. For device reuse, signatures have to be either used by all mounts of a device or by none. Optional. verity.oncorruption=ignore|restart|panic Instruct the kernel to ignore, reboot or panic when corruption is detected. By default the I/O operation simply fails. Requires Linux 4.1 or newer, and libcrypsetup 2.3.4 or newer. Optional. Supported since util-linux v2.35. For example commands: mksquashfs /etc /tmp/etc.raw veritysetup format /tmp/etc.raw /tmp/etc.verity --root-hash-file=/tmp/etc.roothash openssl smime -sign -in /tmp/etc.roothash -nocerts -inkey private.key \ -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s mount -o verity.hashdevice=/tmp/etc.verity,verity.roothashfile=/tmp/etc.roothash,\ verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.raw /mnt create squashfs image from /etc directory, verity hash device and mount verified filesystem image to /mnt. The kernel will verify that the root hash is signed by a key from the kernel keyring if roothashsig is used. LOOP-DEVICE SUPPORT top One further possible type is a mount via the loop device. For example, the command mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3 will set up the loop device /dev/loop3 to correspond to the file /tmp/disk.img, and then mount this device on /mnt. If no explicit loop device is mentioned (but just an option '-o loop' is given), then mount will try to find some unused loop device and use that, for example mount /tmp/disk.img /mnt -o loop The mount command automatically creates a loop device from a regular file if a filesystem type is not specified or the filesystem is known for libblkid, for example: mount /tmp/disk.img /mnt mount -t ext4 /tmp/disk.img /mnt This type of mount knows about three options, namely loop, offset and sizelimit, that are really options to losetup(8). (These options can be used in addition to those specific to the filesystem type.) Since Linux 2.6.25 auto-destruction of loop devices is supported, meaning that any loop device allocated by mount will be freed by umount independently of /etc/mtab. You can also free a loop device by hand, using losetup -d or umount -d. Since util-linux v2.29, mount re-uses the loop device rather than initializing a new device if the same backing file is already used for some loop device with the same offset and sizelimit. This is necessary to avoid a filesystem corruption. EXIT STATUS top mount has the following exit status values (the bits can be ORed): 0 success 1 incorrect invocation or permissions 2 system error (out of memory, cannot fork, no more loop devices) 4 internal mount bug 8 user interrupt 16 problems writing or locking /etc/mtab 32 mount failure 64 some mount succeeded The command mount -a returns 0 (all succeeded), 32 (all failed), or 64 (some failed, some succeeded). EXTERNAL HELPERS top The syntax of external mount helpers is: /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t type.subtype] where the suffix is the filesystem type and the -sfnvoN options have the same meaning as the normal mount options. The -t option is used for filesystems with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs). The command mount does not pass the mount options unbindable, runbindable, private, rprivate, slave, rslave, shared, rshared, auto, noauto, comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers. All other options are used in a comma-separated list as an argument to the -o option. ENVIRONMENT top LIBMOUNT_FORCE_MOUNT2={always|never|auto} force to use classic mount(2) system call (requires support for new file descriptors based mount API). The default is auto; in this case, libmount tries to be smart and use classic mount(2) only for well-known issues. If the new mount API is unavailable, libmount can still use traditional mount(2), although LIBMOUNT_FORCE_MOUNT2 is set to never. LIBMOUNT_FSTAB=<path> overrides the default location of the fstab file (ignored for suid) LIBMOUNT_DEBUG=all enables libmount debug output LIBBLKID_DEBUG=all enables libblkid debug output LOOPDEV_DEBUG=all enables loop device setup debug output FILES top See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section above. /etc/fstab filesystem table /run/mount libmount private runtime directory /etc/mtab table of mounted filesystems or symlink to /proc/mounts /etc/mtab~ lock file (unused on systems with mtab symlink) /etc/mtab.tmp temporary file (unused on systems with mtab symlink) /etc/filesystems a list of filesystem types to try HISTORY top A mount command existed in Version 5 AT&T UNIX. BUGS top It is possible for a corrupted filesystem to cause a crash. Some Linux filesystems dont support -o sync and -o dirsync (the ext2, ext3, ext4, fat and vfat filesystems do support synchronous updates (a la BSD) when mounted with the sync option). The -o remount may not be able to change mount parameters (all ext2fs-specific parameters, except sb, are changeable with a remount, for example, but you cant change gid or umask for the fatfs). It is possible that the files /etc/mtab and /proc/mounts dont match on systems with a regular mtab file. The first file is based only on the mount command options, but the content of the second file also depends on the kernel and others settings (e.g. on a remote NFS server in certain cases the mount command may report unreliable information about an NFS mount point and the /proc/mount file usually contains more reliable information.) This is another reason to replace the mtab file with a symlink to the /proc/mounts file. Checking files on NFS filesystems referenced by file descriptors (i.e. the fcntl and ioctl families of functions) may lead to inconsistent results due to the lack of a consistency check in the kernel even if the noac mount option is used. The loop option with the offset or sizelimit options used may fail when using older kernels if the mount command cant confirm that the size of the block device has been configured as requested. This situation can be worked around by using the losetup(8) command manually before calling mount with the configured loop device. AUTHORS top Karel Zak <kzak@redhat.com> SEE ALSO top mount(2), umount(2), filesystems(5), fstab(5), nfs(5), xfs(5), mount_namespaces(7), xattr(7), e2label(8), findmnt(8), losetup(8), lsblk(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8), umount(8), xfs_admin(8) REPORTING BUGS top For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY top The mount command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at https://www.kernel.org/pub/linux/utils/util-linux/. If you have a bug report for this manual page, send it to util-linux@vger.kernel.org. This page was obtained from the project's upstream Git repository git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org util-linux 2.39.594-1e0ad 2023-08-25 MOUNT(8) Pages that refer to this page: eject(1), fusermount3(1), homectl(1), mountpoint(1), quotasync(1), systemd-dissect(1), systemd-mount(1), unshare(1), chown(2), fcntl(2), fsync(2), ioctl_iflags(2), mount(2), open(2), open_by_handle_at(2), umount(2), getmntent(3), getsubopt(3), fd(4), hd(4), loop(4), ram(4), autofs(5), ext4(5), filesystems(5), fstab(5), lxc.container.conf(5), nfs(5), nfsmount.conf(5), proc(5), repart.d(5), systemd.automount(5), systemd.exec(5), systemd.mount(5), tmpfs(5), xfs(5), bootparam(7), fanotify(7), file-hierarchy(7), hier(7), inode(7), man-pages(7), mount_namespaces(7), spufs(7), automount(8), blkid(8), btrfs-subvolume(8), e4crypt(8), e4defrag(8), findmnt(8), fsck.cramfs(8), fsck.xfs(8), fsfreeze(8), fstrim(8), lsof(8), mkfs.cramfs(8), mount(8), mount.fuse3(8), mount.nfs(8), pam_namespace(8), pivot_root(8), quotaon(8), swapon(8), switch_root(8), systemd-remount-fs.service(8), tune2fs(8), umount(8), wipefs(8), xfs_admin(8), xfs_db(8), xfs_freeze(8), xfs_growfs(8), xfs_info(8), xfs_logprint(8), xfs_rtcp(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if "\[$VLABEL\]" is mounted and save the result in variable "AMV" Bash Command:<START>AMV=$(mount -l | grep "\[$VLABEL\]")<END>

Check if "~/mnt/sdc1" is mounted

mount | grep -q ~/mnt/sdc1

['grep', 'mount']

Output a Bash command to accomplish the following task. Task: Check if "~/mnt/sdc1" is mounted Bash Command:<START>mount | grep -q ~/mnt/sdc1<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # mount\n\n> Provides access to an entire filesystem in one directory.\n> More information: <https://manned.org/mount.8>.\n\n- Show all mounted filesystems:\n\n`mount`\n\n- Mount a device to a directory:\n\n`mount -t {{filesystem_type}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Create a specific directory if it does not exist and mount a device to it:\n\n`mount --mkdir {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a device to a directory for a specific user:\n\n`mount -o uid={{user_id}},gid={{group_id}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a CD-ROM device (with the filetype ISO9660) to `/cdrom` (readonly):\n\n`mount -t {{iso9660}} -o ro {{/dev/cdrom}} {{/cdrom}}`\n\n- Mount all the filesystem defined in `/etc/fstab`:\n\n`mount -a`\n\n- Mount a specific filesystem described in `/etc/fstab` (e.g. `/dev/sda1 /my_drive ext2 defaults 0 2`):\n\n`mount {{/my_drive}}`\n\n- Mount a directory to another directory:\n\n`mount --bind {{path/to/old_dir}} {{path/to/new_dir}}`\n Task: Check if "~/mnt/sdc1" is mounted Bash Command:<START>mount | grep -q ~/mnt/sdc1<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. mount(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training mount(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND-LINE OPTIONS | FILESYSTEM-INDEPENDENT MOUNT OPTIONS | FILESYSTEM-SPECIFIC MOUNT OPTIONS | DM-VERITY SUPPORT | LOOP-DEVICE SUPPORT | EXIT STATUS | EXTERNAL HELPERS | ENVIRONMENT | FILES | HISTORY | BUGS | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY MOUNT(8) System Administration MOUNT(8) NAME top mount - mount a filesystem SYNOPSIS top mount [-h|-V] mount [-l] [-t fstype] mount -a [-fFnrsvw] [-t fstype] [-O optlist] mount [-fnrsvw] [-o options] device|mountpoint mount [-fnrsvw] [-t fstype] [-o options] device mountpoint mount --bind|--rbind|--move olddir newdir mount --make-[shared|slave|private|unbindable|rshared|rslave|rprivate|runbindable] mountpoint DESCRIPTION top All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the filesystem found on some device to the big file tree. Conversely, the umount(8) command will detach it again. The filesystem is used to control how data is stored on the device or provided in a virtual way by network or other services. The standard form of the mount command is: mount -t type device dir This tells the kernel to attach the filesystem found on device (which is of type type) at the directory dir. The option -t type is optional. The mount command is usually able to detect a filesystem. The root permissions are necessary to mount a filesystem by default. See section "Non-superuser mounts" below for more details. The previous contents (if any) and owner and mode of dir become invisible, and as long as this filesystem remains mounted, the pathname dir refers to the root of the filesystem on device. If only the directory or the device is given, for example: mount /dir then mount looks for a mountpoint (and if not found then for a device) in the /etc/fstab file. Its possible to use the --target or --source options to avoid ambiguous interpretation of the given argument. For example: mount --target /mountpoint The same filesystem may be mounted more than once, and in some cases (e.g., network filesystems) the same filesystem may be mounted on the same mountpoint multiple times. The mount command does not implement any policy to control this behavior. All behavior is controlled by the kernel and it is usually specific to the filesystem driver. The exception is --all, in this case already mounted filesystems are ignored (see --all below for more details). Listing the mounts The listing mode is maintained for backward compatibility only. For more robust and customizable output use findmnt(8), especially in your scripts. Note that control characters in the mountpoint name are replaced with '?'. The following command lists all mounted filesystems (of type type): mount [-l] [-t type] The option -l adds labels to this listing. See below. Indicating the device and filesystem Most devices are indicated by a filename (of a block special device), like /dev/sda1, but there are other possibilities. For example, in the case of an NFS mount, device may look like knuth.cwi.nl:/dir. The device names of disk partitions are unstable; hardware reconfiguration, and adding or removing a device can cause changes in names. This is the reason why its strongly recommended to use filesystem or partition identifiers like UUID or LABEL. Currently supported identifiers (tags): LABEL=label Human readable filesystem identifier. See also -L. UUID=uuid Filesystem universally unique identifier. The format of the UUID is usually a series of hex digits separated by hyphens. See also -U. Note that mount uses UUIDs as strings. The UUIDs from the command line or from fstab(5) are not converted to internal binary representation. The string representation of the UUID should be based on lower case characters. PARTLABEL=label Human readable partition identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). PARTUUID=uuid Partition universally unique identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). ID=id Hardware block device ID as generated by udevd. This identifier is usually based on WWN (unique storage identifier) and assigned by the hardware manufacturer. See ls /dev/disk/by-id for more details, this directory and running udevd is required. This identifier is not recommended for generic use as the identifier is not strictly defined and it depends on udev, udev rules and hardware. The command lsblk --fs provides an overview of filesystems, LABELs and UUIDs on available block devices. The command blkid -p <device> provides details about a filesystem on the specified device. Dont forget that there is no guarantee that UUIDs and labels are really unique, especially if you move, share or copy the device. Use lsblk -o +UUID,PARTUUID to verify that the UUIDs are really unique in your system. The recommended setup is to use tags (e.g. UUID=uuid) rather than /dev/disk/by-{label,uuid,id,partuuid,partlabel} udev symlinks in the /etc/fstab file. Tags are more readable, robust and portable. The mount(8) command internally uses udev symlinks, so the use of symlinks in /etc/fstab has no advantage over tags. For more details see libblkid(3). The proc filesystem is not associated with a special device, and when mounting it, an arbitrary keyword - for example, proc - can be used instead of a device specification. (The customary choice none is less fortunate: the error message 'none already mounted' from mount can be confusing.) The files /etc/fstab, /etc/mtab and /proc/mounts The file /etc/fstab (see fstab(5)), may contain lines describing what devices are usually mounted where, using which options. The default location of the fstab(5) file can be overridden with the --fstab path command-line option (see below for more details). The command mount -a [-t type] [-O optlist] (usually given in a bootscript) causes all filesystems mentioned in fstab (of the proper type and/or having or not having the proper options) to be mounted as indicated, except for those whose line contains the noauto keyword. Adding the -F option will make mount fork, so that the filesystems are mounted in parallel. When mounting a filesystem mentioned in fstab or mtab, it suffices to specify on the command line only the device, or only the mount point. The programs mount and umount(8) traditionally maintained a list of currently mounted filesystems in the file /etc/mtab. The support for regular classic /etc/mtab is completely disabled at compile time by default, because on current Linux systems it is better to make /etc/mtab a symlink to /proc/mounts instead. The regular mtab file maintained in userspace cannot reliably work with namespaces, containers and other advanced Linux features. If the regular mtab support is enabled, then its possible to use the file as well as the symlink. If no arguments are given to mount, the list of mounted filesystems is printed. If you want to override mount options from /etc/fstab, you have to use the -o option: mount device|dir -o options and then the mount options from the command line will be appended to the list of options from /etc/fstab. This default behaviour can be changed using the --options-mode command-line option. The usual behavior is that the last option wins if there are conflicting ones. The mount program does not read the /etc/fstab file if both device (or LABEL, UUID, ID, PARTUUID or PARTLABEL) and dir are specified. For example, to mount device foo at /dir: mount /dev/foo /dir This default behaviour can be changed by using the --options-source-force command-line option to always read configuration from fstab. For non-root users mount always reads the fstab configuration. Non-superuser mounts Normally, only the superuser can mount filesystems. However, when fstab contains the user option on a line, anybody can mount the corresponding filesystem. Thus, given a line /dev/cdrom /cd iso9660 ro,user,noauto,unhide any user can mount the iso9660 filesystem found on an inserted CDROM using the command: mount /cd Note that mount is very strict about non-root users and all paths specified on command line are verified before fstab is parsed or a helper program is executed. Its strongly recommended to use a valid mountpoint to specify filesystem, otherwise mount may fail. For example its a bad idea to use NFS or CIFS source on command line. Since util-linux 2.35, mount does not exit when user permissions are inadequate according to libmounts internal security rules. Instead, it drops suid permissions and continues as regular non-root user. This behavior supports use-cases where root permissions are not necessary (e.g., fuse filesystems, user namespaces, etc). For more details, see fstab(5). Only the user that mounted a filesystem can unmount it again. If any user should be able to unmount it, then use users instead of user in the fstab line. The owner option is similar to the user option, with the restriction that the user must be the owner of the special file. This may be useful e.g. for /dev/fd if a login script makes the console user owner of this device. The group option is similar, with the restriction that the user must be a member of the group of the special file. The user mount option is accepted if no username is specified. If used in the format user=someone, the option is silently ignored and visible only for external mount helpers (/sbin/mount.<type>) for compatibility with some network filesystems. Bind mount operation Remount part of the file hierarchy somewhere else. The call is: mount --bind olddir newdir or by using this fstab entry: /olddir /newdir none bind After this call the same contents are accessible in two places. It is important to understand that "bind" does not create any second-class or special node in the kernel VFS. The "bind" is just another operation to attach a filesystem. There is nowhere stored information that the filesystem has been attached by a "bind" operation. The olddir and newdir are independent and the olddir may be unmounted. One can also remount a single file (on a single file). Its also possible to use a bind mount to create a mountpoint from a regular directory, for example: mount --bind foo foo The bind mount call attaches only (part of) a single filesystem, not possible submounts. The entire file hierarchy including submounts can be attached a second place by using: mount --rbind olddir newdir Note that the filesystem mount options maintained by the kernel will remain the same as those on the original mount point. The userspace mount options (e.g., _netdev) will not be copied by mount and its necessary to explicitly specify the options on the mount command line. Since util-linux 2.27 mount permits changing the mount options by passing the relevant options along with --bind. For example: mount -o bind,ro foo foo This feature is not supported by the Linux kernel; it is implemented in userspace by an additional mount(2) remounting system call. This solution is not atomic. The alternative (classic) way to create a read-only bind mount is to use the remount operation, for example: mount --bind olddir newdir mount -o remount,bind,ro olddir newdir Note that a read-only bind will create a read-only mountpoint (VFS entry), but the original filesystem superblock will still be writable, meaning that the olddir will be writable, but the newdir will be read-only. Its also possible to change nosuid, nodev, noexec, noatime, nodiratime, relatime and nosymfollow VFS entry flags via a "remount,bind" operation. The other flags (for example filesystem-specific flags) are silently ignored. The classic mount(2) system call does not allow to change mount options recursively (for example with -o rbind,ro). The recursive semantic is possible with a new mount_setattr(2) kernel system call and its supported since libmount from util-linux v2.39 by a new experimental "recursive" option argument (e.g. -o rbind,ro=recursive). For more details see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS section. Since util-linux 2.31, mount ignores the bind flag from /etc/fstab on a remount operation (if -o remount is specified on command line). This is necessary to fully control mount options on remount by command line. In previous versions the bind flag has been always applied and it was impossible to re-define mount options without interaction with the bind semantic. This mount behavior does not affect situations when "remount,bind" is specified in the /etc/fstab file. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink. This feature is usable (only) with the new kernel mount API where bind mount over symlinks is supported. The move operation Move a mounted tree to another place (atomically). The call is: mount --move olddir newdir This will cause the contents which previously appeared under olddir to now be accessible under newdir. The physical location of the files is not changed. Note that olddir has to be a mountpoint. Note also that moving a mount residing under a shared mount is invalid and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current propagation flags. Shared subtree operations Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, private, slave or unbindable. A shared mount provides the ability to create mirrors of that mount such that mounts and unmounts within any of the mirrors propagate to the other mirror. A slave mount receives propagation from its master, but not vice versa. A private mount carries no propagation abilities. An unbindable mount is a private mount which cannot be cloned through a bind operation. The detailed semantics are documented in Documentation/filesystems/sharedsubtree.txt file in the kernel source tree; see also mount_namespaces(7). Supported operations are: mount --make-shared mountpoint mount --make-slave mountpoint mount --make-private mountpoint mount --make-unbindable mountpoint The following commands allow one to recursively change the type of all the mounts under a given mountpoint. mount --make-rshared mountpoint mount --make-rslave mountpoint mount --make-rprivate mountpoint mount --make-runbindable mountpoint mount does not read fstab(5) when a --make-* operation is requested. All necessary information has to be specified on the command line. Note that the Linux kernel does not allow changing multiple propagation flags with a single mount(2) system call, and the flags cannot be mixed with other mount options and operations. Since util-linux 2.23 the mount command can be used to do more propagation (topology) changes by one mount(8) call and do it also together with other mount operations. The propagation flags are applied by additional mount(2) system calls when the preceding mount operations were successful. Note that this use case is not atomic. It is possible to specify the propagation flags in fstab(5) as mount options (private, slave, shared, unbindable, rprivate, rslave, rshared, runbindable). For example: mount --make-private --make-unbindable /dev/sda1 /foo is the same as: mount /dev/sda1 /foo mount --make-private /foo mount --make-unbindable /foo COMMAND-LINE OPTIONS top The full set of mount options used by an invocation of mount is determined by first extracting the mount options for the filesystem from the fstab table, then applying any options specified by the -o argument, and finally applying a -r or -w option, when present. The mount command does not pass all command-line options to the /sbin/mount.suffix mount helpers. The interface between mount and the mount helpers is described below in the EXTERNAL HELPERS section. Command-line options available for the mount command are: -a, --all Mount all filesystems (of the given types) mentioned in fstab (except for those whose line contains the noauto keyword). The filesystems are mounted following their order in fstab. The mount command compares filesystem source, target (and fs root for bind mount or btrfs) to detect already mounted filesystems. The kernel table with already mounted filesystems is cached during mount --all. This means that all duplicated fstab entries will be mounted. The correct functionality depends on /proc (to detect already mounted filesystems) and on /sys (to evaluate filesystem tags like UUID= or LABEL=). Its strongly recommended to mount /proc and /sys filesystems before mount -a is executed, or keep /proc and /sys at the beginning of fstab. The option --all is possible to use for remount operation too. In this case all filters (-t and -O) are applied to the table of already mounted filesystems. Since version 2.35 it is possible to use the command line option -o to alter mount options from fstab (see also --options-mode). Note that it is a bad practice to use mount -a for fstab checking. The recommended solution is findmnt --verify. -B, --bind Remount a subtree somewhere else (so that its contents are available in both places). See above, under Bind mount operation. -c, --no-canonicalize Dont canonicalize paths. The mount command canonicalizes all paths (from the command line or fstab) by default. The option is designed for mount helpers which call mount -i. It is strongly recommended to not use this command-line option for normal mount operations. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink (see "Bind mount operation" section for more details). Note that mount does not pass this option to the /sbin/mount.type helpers. -F, --fork (Used in conjunction with -a.) Fork off a new incarnation of mount for each device. This will do the mounts on different devices or different NFS servers in parallel. This has the advantage that it is faster; also NFS timeouts proceed in parallel. A disadvantage is that the order of the mount operations is undefined. Thus, you cannot use this option if you want to mount both /usr and /usr/spool. -f, --fake Causes everything to be done except for the mount-related system calls. The --fake option was originally designed to write an entry to /etc/mtab without actually mounting. The /etc/mtab is no longer maintained in userspace, and starting from version 2.39, the mount operation can be a complex chain of operations with dependencies between the syscalls. The --fake option forces libmount to skip all mount source preparation, mount option analysis, and the actual mounting process. The difference between fake and non-fake execution is huge. This is the reason why the --fake option has minimal significance for the current mount(8) implementation and it is maintained mostly for backward compatibility. -i, --internal-only Dont call the /sbin/mount.filesystem helper even if it exists. -L, --label label Mount the partition that has the specified label. -l, --show-labels Add the labels in the mount output. mount must have permission to read the disk device (e.g. be set-user-ID root) for this to work. One can set such a label for ext2, ext3 or ext4 using the e2label(8) utility, or for XFS using xfs_admin(8), or for reiserfs using reiserfstune(8). -M, --move Move a subtree to some other place. See above, the subsection The move operation. -m, --mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. Alias to "-o X-mount.mkdir[=mode]", the default mode is 0755. For more details see X-mount.mkdir below. --map-groups, --map-users inner:_outer_:_count_ Add the specified user/group mapping to an X-mount.idmap map. These options can be given multiple times to build up complete mappings for users and groups. For more details see X-mount.idmap below. --map-users /proc/PID/ns/user Use the specified user namespace for user and group mapping in an id-mapped mount. This is an alias for "-o X-mount.idmap=/proc/PID/ns/user" and cannot be used twice nor together with the inner:_outer_:_count_ option format above. For more details see X-mount.idmap below. -n, --no-mtab Mount without writing in /etc/mtab. This is necessary for example when /etc is on a read-only filesystem. -N, --namespace ns Perform the mount operation in the mount namespace specified by ns. ns is either PID of process running in that namespace or special file representing that namespace. mount switches to the mount namespace when it reads /etc/fstab, writes /etc/mtab: (or writes to _/run/mount) and calls mount(2), otherwise it runs in the original mount namespace. This means that the target namespace does not have to contain any libraries or other requirements necessary to execute the mount(2) call. See mount_namespaces(7) for more information. -O, --test-opts opts Limit the set of filesystems to which the -a option applies. In this regard it is like the -t option except that -O is useless without -a. For example, the command mount -a -O no_netdev mounts all filesystems except those which have the option netdev specified in the options field in the /etc/fstab file. It is different from -t in that each option is matched exactly; a leading no at the beginning of one option does not negate the rest. The -t and -O options are cumulative in effect; that is, the command mount -a -t ext2 -O _netdev mounts all ext2 filesystems with the _netdev option, not all filesystems that are either ext2 or have the _netdev option specified. -o, --options opts Use the specified mount options. The opts argument is a comma-separated list. For example: mount LABEL=mydisk -o noatime,nodev,nosuid Note that the order of the options matters, as the last option wins if there are conflicting ones. The options from the command line also overwrite options from fstab by default. For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections. --onlyonce Forces mount command to check if the filesystem is already mounted. This behavior is the default for --all; otherwise, it depends on the kernel filesystem driver. Some filesystems may be mounted more than once on the same mount point (e.g. tmpfs). --options-mode mode Controls how to combine options from fstab/mtab with options from the command line. mode can be one of ignore, append, prepend or replace. For example, append means that options from fstab are appended to options from the command line. The default value is prepend it means command line options are evaluated after fstab options. Note that the last option wins if there are conflicting ones. --options-source source Source of default options. source is a comma-separated list of fstab, mtab and disable. disable disables fstab and mtab and enables --options-source-force. The default value is fstab,mtab. --options-source-force Use options from fstab/mtab even if both device and dir are specified. -R, --rbind Remount a subtree and all possible submounts somewhere else (so that its contents are available in both places). See above, the subsection Bind mount operation. -r, --read-only Mount the filesystem read-only. A synonym is -o ro. Note that, depending on the filesystem type, state and kernel behavior, the system may still write to the device. For example, ext3 and ext4 will replay the journal if the filesystem is dirty. To prevent this kind of write access, you may want to mount an ext3 or ext4 filesystem with the ro,noload mount options or set the block device itself to read-only mode, see the blockdev(8) command. -s Tolerate sloppy mount options rather than failing. This will ignore mount options not supported by a filesystem type. Not all filesystems support this option. Currently its supported by the mount.nfs mount helper only. --source device If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount source. --target directory If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount target. --target-prefix directory Prepend the specified directory to all mount targets. This option can be used to follow fstab, but mount operations are done in another place, for example: mount --all --target-prefix /chroot -o X-mount.mkdir mounts all from system fstab to /chroot, all missing mountpoint are created (due to X-mount.mkdir). See also --fstab to use an alternative fstab. -T, --fstab path Specifies an alternative fstab file. If path is a directory, then the files in the directory are sorted by strverscmp(3); files that start with "." or without an .fstab extension are ignored. The option can be specified more than once. This option is mostly designed for initramfs or chroot scripts where additional configuration is specified beyond standard system configuration. Note that mount does not pass the option --fstab to the /sbin/mount.type helpers, meaning that the alternative fstab files will be invisible for the helpers. This is no problem for normal mounts, but user (non-root) mounts always require fstab to verify the users rights. -t, --types fstype The argument following the -t is used to indicate the filesystem type. The filesystem types which are currently supported depend on the running kernel. See /proc/filesystems and /lib/modules/$(uname -r)/kernel/fs for a complete list of the filesystems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs. The programs mount and umount(8) support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For example 'fuse.sshfs'. Its recommended to use subtype notation rather than add any prefix to the mount source (for example 'sshfs#example.com' is deprecated). If no -t option is given, or if the auto type is specified, mount will try to guess the desired type. mount uses the libblkid(3) library for guessing the filesystem type; if that does not turn up anything that looks familiar, mount will try to read the file /etc/filesystems, or, if that does not exist, /proc/filesystems. All of the filesystem types listed there will be tried, except for those that are labeled "nodev" (e.g. devpts, proc and nfs). If /etc/filesystems ends in a line with a single *, mount will read /proc/filesystems afterwards. While trying, all filesystem types will be mounted with the mount option silent. The auto type may be useful for user-mounted floppies. Creating a file /etc/filesystems can be useful to change the probe order (e.g., to try vfat before msdos or ext3 before ext2) or if you use a kernel module autoloader. More than one type may be specified in a comma-separated list, for the -t option as well as in an /etc/fstab entry. The list of filesystem types for the -t option can be prefixed with no to specify the filesystem types on which no action should be taken. The prefix no has no effect when specified in an /etc/fstab entry. The prefix no can be meaningful with the -a option. For example, the command mount -a -t nomsdos,smbfs mounts all filesystems except those of type msdos and smbfs. For most types all the mount program has to do is issue a simple mount(2) system call, and no detailed knowledge of the filesystem type is required. For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems have a separate mount program. In order to make it possible to treat all types in a uniform way, mount will execute the program /sbin/mount.type (if that exists) when called with type type. Since different versions of the smbmount program have different calling conventions, /sbin/mount.smbfs may have to be a shell script that sets up the desired call. -U, --uuid uuid Mount the partition that has the specified uuid. -v, --verbose Verbose mode. -w, --rw, --read-write Mount the filesystem read/write. Read-write is the kernel default and the mount default is to try read-only if the previous mount(2) syscall with read-write flags on write-protected devices failed. A synonym is -o rw. Note that specifying -w on the command line forces mount to never try read-only mount on write-protected devices or already mounted read-only filesystems. -h, --help Display help text and exit. -V, --version Print version and exit. FILESYSTEM-INDEPENDENT MOUNT OPTIONS top Some of these options are only useful when they appear in the /etc/fstab file. Some of these options could be enabled or disabled by default in the system kernel. To check the current setting see the options in /proc/mounts. Note that filesystems also have per-filesystem specific default mount options (see for example tune2fs -l output for extN filesystems). The options nosuid, noexec, nodiratime, relatime, noatime, strictatime, and nosymfollow are interpreted only by the abstract VFS kernel layer and applied to the mountpoint node rather than to the filesystem itself. Try: findmnt -o TARGET,VFS-OPTIONS,FS-OPTIONS to get a complete overview of filesystems and VFS options. The read-only setting (ro or rw) is interpreted by VFS and the filesystem and depends on how the option is specified on the mount(8) command line. The default is to interpret it on the filesystem level. The operation "-o bind,remount,ro" is applied only to the VFS mountpoint, and operation "-o remount,ro" is applied to VFS and filesystem superblock. This semantic allows create a read-only mountpoint but keeps the filesystem writable from another mountpoint. Since v2.39 libmount can use a new kernel mount interface to set the VFS options recursive. For backward compatibility, this feature is not enabled by default, although recursive operation (e.g. rbind) has been requested. The new option argument "recursive" could be specified, for example: mount -orbind,ro=recursive,noexec=recursive,nosuid /foo /bar recursively binds filesystems from /foo to /bar, /bar, and all submounts will be read-only and noexec, but only /bar itself will be "nosuid". The "recursive" optional argument for VFS mount options is an EXPERIMENTAL feature. The following options apply to any filesystem that is being mounted (but not every filesystem actually honors them - e.g., the sync option today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs): async All I/O to the filesystem should be done asynchronously. (See also the sync option.) atime Do not use the noatime feature, so the inode access time is controlled by kernel defaults. See also the descriptions of the relatime and strictatime mount options. noatime Do not update inode access times on this filesystem (e.g. for faster access on the news spool to speed up news servers). This works for all inode types (directories too), so it implies nodiratime. auto Can be mounted with the -a option. noauto Can only be mounted explicitly (i.e., the -a option will not cause the filesystem to be mounted). context=context, fscontext=context, defcontext=context, and rootcontext=context The context= option is useful when mounting filesystems that do not support extended attributes, such as a floppy or hard disk formatted with VFAT, or systems that are not normally running under SELinux, such as an ext3 or ext4 formatted disk from a non-SELinux workstation. You can also use context= on filesystems you do not trust, such as a floppy. It also helps in compatibility with xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where xattrs are supported, you can save time not having to label every file by assigning the entire disk one security context. A commonly used option for removable media is context="system_u:object_r:removable_t. The fscontext= option works for all filesystems, regardless of their xattr support. The fscontext option sets the overarching filesystem label to a specific security context. This filesystem label is separate from the individual labels on the files. It represents the entire filesystem for certain kinds of permission checks, such as during mount or file creation. Individual file labels are still obtained from the xattrs on the files themselves. The context option actually sets the aggregate context that fscontext provides, in addition to supplying the same label for individual files. You can set the default security context for unlabeled files using defcontext= option. This overrides the value set for unlabeled files in the policy and requires a filesystem that supports xattr labeling. The rootcontext= option allows you to explicitly label the root inode of a FS being mounted before that FS or inode becomes visible to userspace. This was found to be useful for things like stateless Linux. The special value @target can be used to assign the current context of the target mountpoint location. Note that the kernel rejects any remount request that includes the context option, even when unchanged from the current context. Warning: the context value might contain commas, in which case the value has to be properly quoted, otherwise mount will interpret the comma as a separator between mount options. Dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t tmpfs none /mnt -o \ 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec' For more details, see selinux(8). defaults Use the default options: rw, suid, dev, exec, auto, nouser, and async. Note that the real set of all default mount options depends on the kernel and filesystem type. See the beginning of this section for more details. dev Interpret character or block special devices on the filesystem. nodev Do not interpret character or block special devices on the filesystem. diratime Update directory inode access times on this filesystem. This is the default. (This option is ignored when noatime is set.) nodiratime Do not update directory inode access times on this filesystem. (This option is implied when noatime is set.) dirsync All directory updates within the filesystem should be done synchronously. This affects the following system calls: creat(2), link(2), unlink(2), symlink(2), mkdir(2), rmdir(2), mknod(2) and rename(2). exec Permit execution of binaries and other executable files. noexec Do not permit direct execution of any binaries on the mounted filesystem. group Allow an ordinary user to mount the filesystem if one of that users groups matches the group of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line group,dev,suid). iversion Every time the inode is modified, the i_version field will be incremented. noiversion Do not increment the i_version inode field. mand Allow mandatory locks on this filesystem. See fcntl(2). This option was deprecated in Linux 5.15. nomand Do not allow mandatory locks on this filesystem. _netdev The filesystem resides on a device that requires network access (used to prevent the system from attempting to mount these filesystems until the network has been enabled on the system). nofail Do not report errors for this device if it does not exist. relatime Update inode access times relative to modify or change time. Access time is only updated if the previous access time was earlier than or equal to the current modify or change time. (Similar to noatime, but it doesnt break mutt(1) or other applications that need to know if a file has been read since the last time it was modified.) Since Linux 2.6.30, the kernel defaults to the behavior provided by this option (unless noatime was specified), and the strictatime option is required to obtain traditional semantics. In addition, since Linux 2.6.30, the files last access time is always updated if it is more than 1 day old. norelatime Do not use the relatime feature. See also the strictatime mount option. strictatime Allows to explicitly request full atime updates. This makes it possible for the kernel to default to relatime or noatime but still allow userspace to override it. For more details about the default system mount options see /proc/mounts. nostrictatime Use the kernels default behavior for inode access time updates. lazytime Only update times (atime, mtime, ctime) on the in-memory version of the file inode. This mount option significantly reduces writes to the inode table for workloads that perform frequent random writes to preallocated files. The on-disk timestamps are updated only when: the inode needs to be updated for some change unrelated to file timestamps the application employs fsync(2), syncfs(2), or sync(2) an undeleted inode is evicted from memory more than 24 hours have passed since the inode was written to disk. nolazytime Do not use the lazytime feature. suid Honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. nosuid Do not honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. In addition, SELinux domain transitions require permission nosuid_transition, which in turn needs also policy capability nnp_nosuid_transition. silent Turn on the silent flag. loud Turn off the silent flag. owner Allow an ordinary user to mount the filesystem if that user is the owner of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line owner,dev,suid). remount Attempt to remount an already-mounted filesystem. This is commonly used to change the mount flags for a filesystem, especially to make a readonly filesystem writable. It does not change device or mount point. The remount operation together with the bind flag has special semantics. See above, the subsection Bind mount operation. The default kernel behavior for VFS mount flags (nodev,nosuid,noexec,ro) is to reset all unspecified flags on remount. Thats why mount(8) tries to keep the current setting according to fstab or /proc/self/mountinfo. This default behavior is possible to change by --options-mode. The recursive change of the mount flags (supported since v2.39 on systems with mount_setattr(2) syscall), for example, mount -o remount,ro=recursive, do not use "reset-unspecified" behavior, and it works as a simple add/remove operation and unspecified flags are not modified. The remount functionality follows the standard way the mount command works with options from fstab. This means that mount does not read fstab (or mtab) only when both device and dir are specified. mount -o remount,rw /dev/foo /dir After this call all old mount options are replaced and arbitrary stuff from fstab (or mtab) is ignored, except the loop= option which is internally generated and maintained by the mount command. mount -o remount,rw /dir After this call, mount reads fstab and merges these options with the options from the command line (-o). If no mountpoint is found in fstab, then it defaults to mount options from /proc/self/mountinfo. mount allows the use of --all to remount all already mounted filesystems which match a specified filter (-O and -t). For example: mount --all -o remount,ro -t vfat remounts all already mounted vfat filesystems in read-only mode. Each of the filesystems is remounted by mount -o remount,ro /dir semantic. This means the mount command reads fstab or mtab and merges these options with the options from the command line. ro Mount the filesystem read-only. rw Mount the filesystem read-write. sync All I/O to the filesystem should be done synchronously. In the case of media with a limited number of write cycles (e.g. some flash drives), sync may cause life-cycle shortening. user Allow an ordinary user to mount the filesystem. The name of the mounting user is written to the mtab file (or to the private libmount file in /run/mount on systems without a regular mtab) so that this same user can unmount the filesystem again. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line user,exec,dev,suid). nouser Forbid an ordinary user to mount the filesystem. This is the default; it does not imply any other options. users Allow any user to mount and to unmount the filesystem, even when some other ordinary user mounted it. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line users,exec,dev,suid). X-* All options prefixed with "X-" are interpreted as comments or as userspace application-specific options. These options are not stored in user space (e.g., mtab file), nor sent to the mount.type helpers nor to the mount(2) system call. The suggested format is X-appname.option. x-* The same as X-* options, but stored permanently in user space. This means the options are also available for umount(8) or other operations. Note that maintaining mount options in user space is tricky, because its necessary use libmount-based tools and there is no guarantee that the options will be always available (for example after a move mount operation or in unshared namespace). Note that before util-linux v2.30 the x-* options have not been maintained by libmount and stored in user space (functionality was the same as for X-* now), but due to the growing number of use-cases (in initrd, systemd etc.) the functionality has been extended to keep existing fstab configurations usable without a change. X-mount.auto-fstypes=list Specifies allowed or forbidden filesystem types for automatic filesystem detection. The list is a comma-separated list of the filesystem names. The automatic filesystem detection is triggered by the "auto" filesystem type or when the filesystem type is not specified. Thy list follows how mount evaluates type patterns (see -t for more details). Only specified filesystem types are allowed, or all specified types are forbidden if the list is prefixed by "no". For example, X-mount.auto-fstypes="ext4,btrfs" accepts only ext4 and btrfs, and X-mount.auto-fstypes="novfat,xfs" accepts all filesystems except vfat and xfs. Note that comma is used as a separator between mount options, it means that auto-fstypes values have to be properly quoted, dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t auto -oX-mount.auto-fstypes="noext2,ext3"' /dev/sdc1 /mnt/test X-mount.mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. The optional argument mode specifies the filesystem access mode used for mkdir(2) in octal notation. The default mode is 0755. This functionality is supported only for root users or when mount is executed without suid permissions. The option is also supported as x-mount.mkdir, but this notation is deprecated since v2.30. See also --mkdir command line option. X-mount.subdir=directory Allow mounting sub-directory from a filesystem instead of the root directory. For now, this feature is implemented by temporary filesystem root directory mount in unshared namespace and then bind the sub-directory to the final mount point and umount the root of the filesystem. The sub-directory mount shows up atomically for the rest of the system although it is implemented by multiple mount(2) syscalls. Note that this feature will not work in session with an unshared private mount namespace (after unshare --mount) on old kernels or with mount(8) without support for file-descriptors-based mount kernel API. In this case, you need unshare --mount --propagation shared. This feature is EXPERIMENTAL. X-mount.owner=username|UID, X-mount.group=group|GID Set mountpoint's ownership after mounting. Names resolved in the target mount namespace, see -N. X-mount.mode=mode Set mountpoint's mode after mounting. X-mount.idmap=id-type:id-mount:id-host:id-range [id-type:id-mount:id-host:id-range], X-mount.idmap=file Use this option to create an idmapped mount. An idmapped mount allows to change ownership of all files located under a mount according to the ID-mapping associated with a user namespace. The ownership change is tied to the lifetime and localized to the relevant mount. The relevant ID-mapping can be specified in two ways: A user can specify the ID-mapping directly. The ID-mapping must be specified using the syntax id-type:id-mount:id-host:id-range. Specifying u as the id-type prefix creates a UID-mapping, g creates a GID-mapping and omitting id-type or specifying b creates both a UID- and GID-mapping. The id-mount parameter indicates the starting ID in the new mount. The id-host parameter indicates the starting ID in the filesystem. The id-range parameter indicates how many IDs are to be mapped. It is possible to specify multiple ID-mappings. The individual ID-mappings must be separated by spaces. For example, the ID-mapping X-mount.idmap=u:1000:0:1 g:1001:1:2 5000:1000:2 creates an idmapped mount where UID 0 is mapped to UID 1000, GID 1 is mapped to GUID 1001, GID 2 is mapped to GID 1002, UID and GID 1000 are mapped to 5000, and UID and GID 1001 are mapped to 5001 in the mount. When an ID-mapping is specified directly a new user namespace will be allocated with the requested ID-mapping. The newly created user namespace will be attached to the mount. A user can specify a user namespace file. The user namespace will then be attached to the mount and the ID-mapping of the user namespace will become the ID-mapping of the mount. For example, X-mount.idmap=/proc/PID/ns/user will attach the user namespace of the process PID to the mount. nosymfollow Do not follow symlinks when resolving paths. Symlinks can still be created, and readlink(1), readlink(2), realpath(1), and realpath(3) all still work properly. FILESYSTEM-SPECIFIC MOUNT OPTIONS top This section lists options that are specific to particular filesystems. Where possible, you should first consult filesystem-specific manual pages for details. Some of those pages are listed in the following table. Filesystem(s) Manual page btrfs btrfs(5) cifs mount.cifs(8) ext2, ext3, ext4 ext4(5) fuse fuse(8) nfs nfs(5) tmpfs tmpfs(5) xfs xfs(5) Note that some of the pages listed above might be available only after you install the respective userland tools. The following options apply only to certain filesystems. We sort them by filesystem. All options follow the -o flag. What options are supported depends a bit on the running kernel. Further information may be available in filesystem-specific files in the kernel source subdirectory Documentation/filesystems. Mount options for adfs uid=value and gid=value Set the owner and group of the files in the filesystem (default: uid=gid=0). ownmask=value and othmask=value Set the permission mask for ADFS 'owner' permissions and 'other' permissions, respectively (default: 0700 and 0077, respectively). See also /usr/src/linux/Documentation/filesystems/adfs.rst. Mount options for affs uid=value and gid=value Set the owner and group of the root of the filesystem (default: uid=gid=0, but with option uid or gid without specified value, the UID and GID of the current process are taken). setuid=value and setgid=value Set the owner and group of all files. mode=value Set the mode of all files to value & 0777 disregarding the original permissions. Add search permission to directories that have read permission. The value is given in octal. protect Do not allow any changes to the protection bits on the filesystem. usemp Set UID and GID of the root of the filesystem to the UID and GID of the mount point upon the first sync or umount, and then clear this option. Strange... verbose Print an informational message for each successful mount. prefix=string Prefix used before volume name, when following a link. volume=string Prefix (of length at most 30) used before '/' when following a symbolic link. reserved=value (Default: 2.) Number of unused blocks at the start of the device. root=value Give explicitly the location of the root block. bs=value Give blocksize. Allowed values are 512, 1024, 2048, 4096. grpquota|noquota|quota|usrquota These options are accepted but ignored. (However, quota utilities may react to such strings in /etc/fstab.) Mount options for debugfs The debugfs filesystem is a pseudo filesystem, traditionally mounted on /sys/kernel/debug. As of kernel version 3.4, debugfs has the following options: uid=n, gid=n Set the owner and group of the mountpoint. mode=value Sets the mode of the mountpoint. Mount options for devpts The devpts filesystem is a pseudo filesystem, traditionally mounted on /dev/pts. In order to acquire a pseudo terminal, a process opens /dev/ptmx; the number of the pseudo terminal is then made available to the process and the pseudo terminal slave can be accessed as /dev/pts/<number>. uid=value and gid=value This sets the owner or the group of newly created pseudo terminals to the specified values. When nothing is specified, they will be set to the UID and GID of the creating process. For example, if there is a tty group with GID 5, then gid=5 will cause newly created pseudo terminals to belong to the tty group. mode=value Set the mode of newly created pseudo terminals to the specified value. The default is 0600. A value of mode=620 and gid=5 makes "mesg y" the default on newly created pseudo terminals. newinstance Create a private instance of the devpts filesystem, such that indices of pseudo terminals allocated in this new instance are independent of indices created in other instances of devpts. All mounts of devpts without this newinstance option share the same set of pseudo terminal indices (i.e., legacy mode). Each mount of devpts with the newinstance option has a private set of pseudo terminal indices. This option is mainly used to support containers in the Linux kernel. It is implemented in Linux kernel versions starting with 2.6.29. Further, this mount option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. To use this option effectively, /dev/ptmx must be a symbolic link to pts/ptmx. See Documentation/filesystems/devpts.txt in the Linux kernel source tree for details. ptmxmode=value Set the mode for the new ptmx device node in the devpts filesystem. With the support for multiple instances of devpts (see newinstance option above), each instance has a private ptmx node in the root of the devpts filesystem (typically /dev/pts/ptmx). For compatibility with older versions of the kernel, the default mode of the new ptmx node is 0000. ptmxmode=value specifies a more useful mode for the ptmx node and is highly recommended when the newinstance option is specified. This option is only implemented in Linux kernel versions starting with 2.6.29. Further, this option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. Mount options for fat (Note: fat is not a separate filesystem, but a common part of the msdos, umsdos and vfat filesystems.) blocksize={512|1024|2048} Set blocksize (default 512). This option is obsolete. uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. dmask=value Set the umask applied to directories only. The default is the umask of the current process. The value is given in octal. fmask=value Set the umask applied to regular files only. The default is the umask of the current process. The value is given in octal. allow_utime=value This option controls the permission check of mtime/atime. 20 If current process is in group of files group ID, you can change timestamp. 2 Other users can change timestamp. The default is set from 'dmask' option. (If the directory is writable, utime(2) is also allowed. I.e. ~dmask & 022) Normally utime(2) checks that the current process is owner of the file, or that it has the CAP_FOWNER capability. But FAT filesystems dont have UID/GID on disk, so the normal check is too inflexible. With this option you can relax it. check=value Three different levels of pickiness can be chosen: r[elaxed] Upper and lower case are accepted and equivalent, long name parts are truncated (e.g. verylongname.foobar becomes verylong.foo), leading and embedded spaces are accepted in each name part (name and extension). n[ormal] Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are rejected. This is the default. s[trict] Like "normal", but names that contain long parts or special characters that are sometimes used on Linux but are not accepted by MS-DOS (+, =, etc.) are rejected. codepage=value Sets the codepage for converting to shortname characters on FAT and VFAT filesystems. By default, codepage 437 is used. conv=mode This option is obsolete and may fail or be ignored. cvf_format=module Forces the driver to use the CVF (Compressed Volume File) module cvf_module instead of auto-detection. If the kernel supports kmod, the cvf_format=xxx option also controls on-demand CVF module loading. This option is obsolete. cvf_option=option Option passed to the CVF module. This option is obsolete. debug Turn on the debug flag. A version string and a list of filesystem parameters will be printed (these data are also printed if the parameters appear to be inconsistent). discard If set, causes discard/TRIM commands to be issued to the block device when blocks are freed. This is useful for SSD devices and sparse/thinly-provisioned LUNs. dos1xfloppy If set, use a fallback default BIOS Parameter Block configuration, determined by backing device size. These static parameters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images. errors={panic|continue|remount-ro} Specify FAT behavior on critical errors: panic, continue without doing anything, or remount the partition in read-only mode (default behavior). fat={12|16|32} Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT type detection routine. Use with caution! iocharset=value Character set to use for converting between 8 bit characters and 16 bit Unicode characters. The default is iso8859-1. Long filenames are stored on disk in Unicode format. nfs={stale_rw|nostale_ro} Enable this only if you want to export the FAT filesystem over NFS. stale_rw: This option maintains an index (cache) of directory inodes which is used by the nfs-related code to improve look-ups. Full file operations (read/write) over NFS are supported but with cache eviction at NFS server, this could result in spurious ESTALE errors. nostale_ro: This option bases the inode number and file handle on the on-disk location of a file in the FAT directory entry. This ensures that ESTALE will not be returned after a file is evicted from the inode cache. However, it means that operations such as rename, create and unlink could cause file handles that previously pointed at one file to point at a different file, potentially causing data corruption. For this reason, this option also mounts the filesystem readonly. To maintain backward compatibility, -o nfs is also accepted, defaulting to stale_rw. tz=UTC This option disables the conversion of timestamps between local time (as used by Windows on FAT) and UTC (which Linux uses internally). This is particularly useful when mounting devices (like digital cameras) that are set to UTC in order to avoid the pitfalls of local time. time_offset=minutes Set offset for conversion of timestamps from local time used by FAT to UTC. I.e., minutes will be subtracted from each timestamp to convert it to UTC used internally by Linux. This is useful when the time zone set in the kernel via settimeofday(2) is not the time zone used by the filesystem. Note that this option still does not provide correct time stamps in all cases in presence of DST - time stamps in a different DST setting will be off by one hour. quiet Turn on the quiet flag. Attempts to chown or chmod files do not return errors, although they fail. Use with caution! rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO of the directory will just be ignored, and is used only by applications as a flag (e.g. its set for the customized folder). If you want to use ATTR_RO as read-only flag even for the directory, set this option. showexec If set, the execute permission bits of the file will be allowed only if the extension part of the name is .EXE, .COM, or .BAT. Not set by default. sys_immutable If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux. Not set by default. flush If set, the filesystem will try to flush to disk more early than normal. Not set by default. usefree Use the "free clusters" value stored on FSINFO. Itll be used to determine number of free clusters without scanning disk. But its not used by default, because recent Windows dont update it correctly in some case. If you are sure the "free clusters" on FSINFO is correct, by this option you can avoid scanning disk. dots, nodots, dotsOK=[yes|no] Various misguided attempts to force Unix or DOS conventions onto a FAT filesystem. Mount options for hfs creator=cccc, type=cccc Set the creator/type values as shown by the MacOS finder used for creating new files. Default values: '????'. uid=n, gid=n Set the owner and group of all files. (Default: the UID and GID of the current process.) dir_umask=n, file_umask=n, umask=n Set the umask used for all directories, all regular files, or all files and directories. Defaults to the umask of the current process. session=n Select the CDROM session to mount. Defaults to leaving that decision to the CDROM driver. This option will fail with anything but a CDROM as underlying device. part=n Select partition number n from the device. Only makes sense for CDROMs. Defaults to not parsing the partition table at all. quiet Dont complain about invalid mount options. Mount options for hpfs uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. case={lower|asis} Convert all files names to lower case, or leave them. (Default: case=lower.) conv=mode This option is obsolete and may fail or being ignored. nocheck Do not abort mounting when certain consistency checks fail. Mount options for iso9660 ISO 9660 is a standard describing a filesystem structure to be used on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the udf filesystem.) Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like restrictions on filename length), and in addition all characters are in upper case. Also there is no field for file ownership, protection, number of links, provision for block/character devices, etc. Rock Ridge is an extension to iso9660 that provides all of these UNIX-like features. Basically there are extensions to each directory record that supply all of the additional information, and when Rock Ridge is in use, the filesystem is indistinguishable from a normal UNIX filesystem (except that it is read-only, of course). norock Disable the use of Rock Ridge extensions, even if available. Cf. map. nojoliet Disable the use of Microsoft Joliet extensions, even if available. Cf. map. check={r[elaxed]|s[trict]} With check=relaxed, a filename is first converted to lower case before doing the lookup. This is probably only meaningful together with norock and map=normal. (Default: check=strict.) uid=value and gid=value Give all files in the filesystem the indicated user or group id, possibly overriding the information found in the Rock Ridge extensions. (Default: uid=0,gid=0.) map={n[ormal]|o[ff]|a[corn]} For non-Rock Ridge volumes, normal name translation maps upper to lower case ASCII, drops a trailing ';1', and converts ';' to '.'. With map=off no name translation is done. See norock. (Default: map=normal.) map=acorn is like map=normal but also apply Acorn extensions if present. mode=value For non-Rock Ridge volumes, give all files the indicated mode. (Default: read and execute permission for everybody.) Octal mode values require a leading 0. unhide Also show hidden and associated files. (If the ordinary files and the associated or hidden files have the same filenames, this may make the ordinary files inaccessible.) block={512|1024|2048} Set the block size to the indicated value. (Default: block=1024.) conv=mode This option is obsolete and may fail or being ignored. cruft If the high byte of the file length contains other garbage, set this mount option to ignore the high order bits of the file length. This implies that a file cannot be larger than 16 MB. session=x Select number of session on a multisession CD. sbsector=xxx Session begins from sector xxx. The following options are the same as for vfat and specifying them only makes sense when using discs encoded using Microsofts Joliet extensions. iocharset=value Character set to use for converting 16 bit Unicode characters on CD to 8 bit characters. The default is iso8859-1. utf8 Convert 16 bit Unicode characters on CD to UTF-8. Mount options for jfs iocharset=name Character set to use for converting from Unicode to ASCII. The default is to do no conversion. Use iocharset=utf8 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in the kernel .config file. resize=value Resize the volume to value blocks. JFS only supports growing a volume, not shrinking it. This option is only valid during a remount, when the volume is mounted read-write. The resize keyword with no value will grow the volume to the full size of the partition. nointegrity Do not write to the journal. The primary use of this option is to allow for higher performance when restoring a volume from backup media. The integrity of the volume is not guaranteed if the system abnormally ends. integrity Default. Commit metadata changes to the journal. Use this option to remount a volume where the nointegrity option was previously specified in order to restore normal behavior. errors={continue|remount-ro|panic} Define the behavior when an error is encountered. (Either ignore errors and just mark the filesystem erroneous and continue, or remount the filesystem read-only, or panic and halt the system.) noquota|quota|usrquota|grpquota These options are accepted but ignored. Mount options for msdos See mount options for fat. If the msdos filesystem detects an inconsistency, it reports an error and sets the file system read-only. The filesystem can be made writable again by remounting it. Mount options for ncpfs Just like nfs, the ncpfs implementation expects a binary argument (a struct ncp_mount_data) to the mount(2) system call. This argument is constructed by ncpmount(8) and the current version of mount (2.12) does not know anything about ncpfs. Mount options for ntfs iocharset=name Character set to use when returning file names. Unlike VFAT, NTFS suppresses names that contain nonconvertible characters. Deprecated. nls=name New name for the option earlier called iocharset. utf8 Use UTF-8 for converting file names. uni_xlate={0|1|2} For 0 (or 'no' or 'false'), do not use escape sequences for unknown Unicode characters. For 1 (or 'yes' or 'true') or 2, use vfat-style 4-byte escape sequences starting with ":". Here 2 gives a little-endian encoding and 1 a byteswapped bigendian encoding. posix=[0|1] If enabled (posix=1), the filesystem distinguishes between upper and lower case. The 8.3 alias names are presented as hard links instead of being suppressed. This option is obsolete. uid=value, gid=value and umask=value Set the file permission on the filesystem. The umask value is given in octal. By default, the files are owned by root and not readable by somebody else. Mount options for overlay Since Linux 3.18 the overlay pseudo filesystem implements a union mount for other filesystems. An overlay filesystem combines two filesystems - an upper filesystem and a lower filesystem. When a name exists in both filesystems, the object in the upper filesystem is visible while the object in the lower filesystem is either hidden or, in the case of directories, merged with the upper object. The lower filesystem can be any filesystem supported by Linux and does not need to be writable. The lower filesystem can even be another overlayfs. The upper filesystem will normally be writable and if it is it must support the creation of trusted.* extended attributes, and must provide a valid d_type in readdir responses, so NFS is not suitable. A read-only overlay of two read-only filesystems may use any filesystem type. The options lowerdir and upperdir are combined into a merged directory by using: mount -t overlay overlay \ -olowerdir=/lower,upperdir=/upper,workdir=/work /merged lowerdir=directory Any filesystem, does not need to be on a writable filesystem. upperdir=directory The upperdir is normally on a writable filesystem. workdir=directory The workdir needs to be an empty directory on the same filesystem as upperdir. userxattr Use the "user.overlay." xattr namespace instead of "trusted.overlay.". This is useful for unprivileged mounting of overlayfs. redirect_dir={on|off|follow|nofollow} If the redirect_dir feature is enabled, then the directory will be copied up (but not the contents). Then the "{trusted|user}.overlay.redirect" extended attribute is set to the path of the original location from the root of the overlay. Finally the directory is moved to the new location. on Redirects are enabled. off Redirects are not created and only followed if "redirect_always_follow" feature is enabled in the kernel/module config. follow Redirects are not created, but followed. nofollow Redirects are not created and not followed (equivalent to "redirect_dir=off" if "redirect_always_follow" feature is not enabled). index={on|off} Inode index. If this feature is disabled and a file with multiple hard links is copied up, then this will "break" the link. Changes will not be propagated to other names referring to the same inode. uuid={on|off} Can be used to replace UUID of the underlying filesystem in file handles with null, and effectively disable UUID checks. This can be useful in case the underlying disk is copied and the UUID of this copy is changed. This is only applicable if all lower/upper/work directories are on the same filesystem, otherwise it will fallback to normal behaviour. nfs_export={on|off} When the underlying filesystems supports NFS export and the "nfs_export" feature is enabled, an overlay filesystem may be exported to NFS. With the "nfs_export" feature, on copy_up of any lower object, an index entry is created under the index directory. The index entry name is the hexadecimal representation of the copy up origin file handle. For a non-directory object, the index entry is a hard link to the upper inode. For a directory object, the index entry has an extended attribute "{trusted|user}.overlay.upper" with an encoded file handle of the upper directory inode. When encoding a file handle from an overlay filesystem object, the following rules apply For a non-upper object, encode a lower file handle from lower inode For an indexed object, encode a lower file handle from copy_up origin For a pure-upper object and for an existing non-indexed upper object, encode an upper file handle from upper inode The encoded overlay file handle includes Header including path type information (e.g. lower/upper) UUID of the underlying filesystem Underlying filesystem encoding of underlying inode This encoding format is identical to the encoding format of file handles that are stored in extended attribute "{trusted|user}.overlay.origin". When decoding an overlay file handle, the following steps are followed Find underlying layer by UUID and path type information. Decode the underlying filesystem file handle to underlying dentry. For a lower file handle, lookup the handle in index directory by name. If a whiteout is found in index, return ESTALE. This represents an overlay object that was deleted after its file handle was encoded. For a non-directory, instantiate a disconnected overlay dentry from the decoded underlying dentry, the path type and index inode, if found. For a directory, use the connected underlying decoded dentry, path type and index, to lookup a connected overlay dentry. Decoding a non-directory file handle may return a disconnected dentry. copy_up of that disconnected dentry will create an upper index entry with no upper alias. When overlay filesystem has multiple lower layers, a middle layer directory may have a "redirect" to lower directory. Because middle layer "redirects" are not indexed, a lower file handle that was encoded from the "redirect" origin directory, cannot be used to find the middle or upper layer directory. Similarly, a lower file handle that was encoded from a descendant of the "redirect" origin directory, cannot be used to reconstruct a connected overlay path. To mitigate the cases of directories that cannot be decoded from a lower file handle, these directories are copied up on encode and encoded as an upper file handle. On an overlay filesystem with no upper layer this mitigation cannot be used NFS export in this setup requires turning off redirect follow (e.g. "redirect_dir=nofollow"). The overlay filesystem does not support non-directory connectable file handles, so exporting with the subtree_check exportfs configuration will cause failures to lookup files over NFS. When the NFS export feature is enabled, all directory index entries are verified on mount time to check that upper file handles are not stale. This verification may cause significant overhead in some cases. Note: the mount options index=off,nfs_export=on are conflicting for a read-write mount and will result in an error. xino={on|off|auto} The "xino" feature composes a unique object identifier from the real object st_ino and an underlying fsid index. The "xino" feature uses the high inode number bits for fsid, because the underlying filesystems rarely use the high inode number bits. In case the underlying inode number does overflow into the high xino bits, overlay filesystem will fall back to the non xino behavior for that inode. For a detailed description of the effect of this option please refer to https://docs.kernel.org/filesystems/overlayfs.html metacopy={on|off} When metadata only copy up feature is enabled, overlayfs will only copy up metadata (as opposed to whole file), when a metadata specific operation like chown/chmod is performed. Full file will be copied up later when file is opened for WRITE operation. In other words, this is delayed data copy up operation and data is copied up when there is a need to actually modify data. volatile Volatile mounts are not guaranteed to survive a crash. It is strongly recommended that volatile mounts are only used if data written to the overlay can be recreated without significant effort. The advantage of mounting with the "volatile" option is that all forms of sync calls to the upper filesystem are omitted. In order to avoid a giving a false sense of safety, the syncfs (and fsync) semantics of volatile mounts are slightly different than that of the rest of VFS. If any writeback error occurs on the upperdirs filesystem after a volatile mount takes place, all sync functions will return an error. Once this condition is reached, the filesystem will not recover, and every subsequent sync call will return an error, even if the upperdir has not experience a new error since the last sync call. When overlay is mounted with "volatile" option, the directory "$workdir/work/incompat/volatile" is created. During next mount, overlay checks for this directory and refuses to mount if present. This is a strong indicator that user should throw away upper and work directories and create fresh one. In very limited cases where the user knows that the system has not crashed and contents of upperdir are intact, The "volatile" directory can be removed. Mount options for reiserfs Reiserfs is a journaling filesystem. conv Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem, using the 3.6 format for newly created objects. This filesystem will no longer be compatible with reiserfs 3.5 tools. hash={rupasov|tea|r5|detect} Choose which hash function reiserfs will use to find files within directories. rupasov A hash invented by Yury Yu. Rupasov. It is fast and preserves locality, mapping lexicographically close file names to close hash values. This option should not be used, as it causes a high probability of hash collisions. tea A Davis-Meyer function implemented by Jeremy Fitzhardinge. It uses hash permuting bits in the name. It gets high randomness and, therefore, low probability of hash collisions at some CPU cost. This may be used if EHASHCOLLISION errors are experienced with the r5 hash. r5 A modified version of the rupasov hash. It is used by default and is the best choice unless the filesystem has huge directories and unusual file-name patterns. detect Instructs mount to detect which hash function is in use by examining the filesystem being mounted, and to write this information into the reiserfs superblock. This is only useful on the first mount of an old format filesystem. hashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. no_unhashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. noborder Disable the border allocator algorithm invented by Yury Yu. Rupasov. This may provide performance improvements in some situations. nolog Disable journaling. This will provide slight performance improvements in some situations at the cost of losing reiserfss fast recovery from crashes. Even with this option turned on, reiserfs still performs all journaling operations, save for actual writes into its journaling area. Implementation of nolog is a work in progress. notail By default, reiserfs stores small files and 'file tails' directly into its tree. This confuses some utilities such as lilo(8). This option is used to disable packing of files into the tree. replayonly Replay the transactions which are in the journal, but do not actually mount the filesystem. Mainly used by reiserfsck. resize=number A remount option which permits online expansion of reiserfs partitions. Instructs reiserfs to assume that the device has number blocks. This option is designed for use with devices which are under logical volume management (LVM). There is a special resizer utility which can be obtained from ftp://ftp.namesys.com/pub/reiserfsprogs. user_xattr Enable Extended User Attributes. See the attr(1) manual page. acl Enable POSIX Access Control Lists. See the acl(5) manual page. barrier=none / barrier=flush This disables / enables the use of write barriers in the journaling code. barrier=none disables, barrier=flush enables (default). This also requires an IO stack which can support barriers, and if reiserfs gets an error on a barrier write, it will disable barriers again with a warning. Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance penalty. If your disks are battery-backed in one way or another, disabling barriers may safely improve performance. Mount options for ubifs UBIFS is a flash filesystem which works on top of UBI volumes. Note that atime is not supported and is always turned off. The device name may be specified as ubiX_Y UBI device number X, volume number Y ubiY UBI device number 0, volume number Y ubiX:NAME UBI device number X, volume with name NAME ubi:NAME UBI device number 0, volume with name NAME Alternative ! separator may be used instead of :. The following mount options are available: bulk_read Enable bulk-read. VFS read-ahead is disabled because it slows down the filesystem. Bulk-Read is an internal optimization. Some flashes may read faster if the data are read at one go, rather than at several read requests. For example, OneNAND can do "read-while-load" if it reads more than one NAND page. no_bulk_read Do not bulk-read. This is the default. chk_data_crc Check data CRC-32 checksums. This is the default. no_chk_data_crc Do not check data CRC-32 checksums. With this option, the filesystem does not check CRC-32 checksum for data, but it does check it for the internal indexing information. This option only affects reading, not writing. CRC-32 is always calculated when writing the data. compr={none|lzo|zlib} Select the default compressor which is used when new files are written. It is still possible to read compressed files if mounted with the none option. Mount options for udf UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical Storage Technology Association, and is often used for DVD-ROM, frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, however, perfectly usable by itself on disk drives, flash drives and other block devices. See also iso9660. uid= Make all files in the filesystem belong to the given user. uid=forget can be specified independently of (or usually in addition to) uid=<user> and results in UDF not storing uids to the media. In fact the recorded uid is the 32-bit overflow uid -1 as defined by the UDF standard. The value is given as either <user> which is a valid user name or the corresponding decimal user id, or the special string "forget". gid= Make all files in the filesystem belong to the given group. gid=forget can be specified independently of (or usually in addition to) gid=<group> and results in UDF not storing gids to the media. In fact the recorded gid is the 32-bit overflow gid -1 as defined by the UDF standard. The value is given as either <group> which is a valid group name or the corresponding decimal group id, or the special string "forget". umask= Mask out the given permissions from all inodes read from the filesystem. The value is given in octal. mode= If mode= is set the permissions of all non-directory inodes read from the filesystem will be set to the given mode. The value is given in octal. dmode= If dmode= is set the permissions of all directory inodes read from the filesystem will be set to the given dmode. The value is given in octal. bs= Set the block size. Default value prior to kernel version 2.6.30 was 2048. Since 2.6.30 and prior to 4.11 it was logical device block size with fallback to 2048. Since 4.11 it is logical block size with fallback to any valid block size between logical device block size and 4096. For other details see the mkudffs(8) 2.0+ manpage, see the COMPATIBILITY and BLOCK SIZE sections. unhide Show otherwise hidden files. undelete Show deleted files in lists. adinicb Embed data in the inode. (default) noadinicb Dont embed data in the inode. shortad Use short UDF address descriptors. longad Use long UDF address descriptors. (default) nostrict Unset strict conformance. iocharset= Set the NLS character set. This requires kernel compiled with CONFIG_UDF_NLS option. utf8 Set the UTF-8 character set. Mount options for debugging and disaster recovery novrs Ignore the Volume Recognition Sequence and attempt to mount anyway. session= Select the session number for multi-session recorded optical media. (default= last session) anchor= Override standard anchor location. (default= 256) lastblock= Set the last block of the filesystem. Unused historical mount options that may be encountered and should be removed uid=ignore Ignored, use uid=<user> instead. gid=ignore Ignored, use gid=<group> instead. volume= Unimplemented and ignored. partition= Unimplemented and ignored. fileset= Unimplemented and ignored. rootdir= Unimplemented and ignored. Mount options for ufs ufstype=value UFS is a filesystem widely used in different operating systems. The problem are differences among implementations. Features of some implementations are undocumented, so its hard to recognize the type of ufs automatically. Thats why the user must specify the type of ufs by mount option. Possible values are: old Old format of ufs, this is the default, read only. (Dont forget to give the -r option.) 44bsd For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD). ufs2 Used in FreeBSD 5.x supported as read-write. 5xbsd Synonym for ufs2. sun For filesystems created by SunOS or Solaris on Sparc. sunx86 For filesystems created by Solaris on x86. hp For filesystems created by HP-UX, read-only. nextstep For filesystems created by NeXTStep (on NeXT station) (currently read only). nextstep-cd For NextStep CDROMs (block_size == 2048), read-only. openstep For filesystems created by OpenStep (currently read only). The same filesystem type is also used by macOS. onerror=value Set behavior on error: panic If an error is encountered, cause a kernel panic. [lock|umount|repair] These mount options dont do anything at present; when an error is encountered only a console message is printed. Mount options for umsdos See mount options for msdos. The dotsOK option is explicitly killed by umsdos. Mount options for vfat First of all, the mount options for fat are recognized. The dotsOK option is explicitly killed by vfat. Furthermore, there are uni_xlate Translate unhandled Unicode characters to special escaped sequences. This lets you backup and restore filenames that are created with any Unicode characters. Without this option, a '?' is used when no translation is possible. The escape character is ':' because it is otherwise invalid on the vfat filesystem. The escape sequence that gets used, where u is the Unicode character, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12). posix Allow two files with names that only differ in case. This option is obsolete. nonumtail First try to make a short name without sequence number, before trying name~num.ext. utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the console. It can be enabled for the filesystem with this option or disabled with utf8=0, utf8=no or utf8=false. If uni_xlate gets set, UTF8 gets disabled. shortname=mode Defines the behavior for creation and display of filenames which fit into 8.3 characters. If a long name for a file exists, it will always be the preferred one for display. There are four modes: lower Force the short name to lower case upon display; store a long name when the short name is not all upper case. win95 Force the short name to upper case upon display; store a long name when the short name is not all upper case. winnt Display the short name as is; store a long name when the short name is not all lower case or all upper case. mixed Display the short name as is; store a long name when the short name is not all upper case. This mode is the default since Linux 2.6.32. Mount options for usbfs devuid=uid and devgid=gid and devmode=mode Set the owner and group and mode of the device files in the usbfs filesystem (default: uid=gid=0, mode=0644). The mode is given in octal. busuid=uid and busgid=gid and busmode=mode Set the owner and group and mode of the bus directories in the usbfs filesystem (default: uid=gid=0, mode=0555). The mode is given in octal. listuid=uid and listgid=gid and listmode=mode Set the owner and group and mode of the file devices (default: uid=gid=0, mode=0444). The mode is given in octal. DM-VERITY SUPPORT top The device-mapper verity target provides read-only transparent integrity checking of block devices using kernel crypto API. The mount command can open the dm-verity device and do the integrity verification before the device filesystem is mounted. Requires libcryptsetup with in libmount (optionally via dlopen(3)). If libcryptsetup supports extracting the root hash of an already mounted device, existing devices will be automatically reused in case of a match. Mount options for dm-verity: verity.hashdevice=path Path to the hash tree device associated with the source volume to pass to dm-verity. verity.roothash=hex Hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothashfile. verity.roothashfile=path Path to file containing the hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothash. verity.hashoffset=offset If the hash tree device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the tree. verity.fecdevice=path Path to the Forward Error Correction (FEC) device associated with the source volume to pass to dm-verity. Optional. Requires kernel built with CONFIG_DM_VERITY_FEC. verity.fecoffset=offset If the FEC device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the FEC area. Optional. verity.fecroots=value Parity bytes for FEC (default: 2). Optional. verity.roothashsig=path Path to pkcs7(1ssl) signature of root hash hex string. Requires crypt_activate_by_signed_key() from cryptsetup and kernel built with CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG. For device reuse, signatures have to be either used by all mounts of a device or by none. Optional. verity.oncorruption=ignore|restart|panic Instruct the kernel to ignore, reboot or panic when corruption is detected. By default the I/O operation simply fails. Requires Linux 4.1 or newer, and libcrypsetup 2.3.4 or newer. Optional. Supported since util-linux v2.35. For example commands: mksquashfs /etc /tmp/etc.raw veritysetup format /tmp/etc.raw /tmp/etc.verity --root-hash-file=/tmp/etc.roothash openssl smime -sign -in /tmp/etc.roothash -nocerts -inkey private.key \ -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s mount -o verity.hashdevice=/tmp/etc.verity,verity.roothashfile=/tmp/etc.roothash,\ verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.raw /mnt create squashfs image from /etc directory, verity hash device and mount verified filesystem image to /mnt. The kernel will verify that the root hash is signed by a key from the kernel keyring if roothashsig is used. LOOP-DEVICE SUPPORT top One further possible type is a mount via the loop device. For example, the command mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3 will set up the loop device /dev/loop3 to correspond to the file /tmp/disk.img, and then mount this device on /mnt. If no explicit loop device is mentioned (but just an option '-o loop' is given), then mount will try to find some unused loop device and use that, for example mount /tmp/disk.img /mnt -o loop The mount command automatically creates a loop device from a regular file if a filesystem type is not specified or the filesystem is known for libblkid, for example: mount /tmp/disk.img /mnt mount -t ext4 /tmp/disk.img /mnt This type of mount knows about three options, namely loop, offset and sizelimit, that are really options to losetup(8). (These options can be used in addition to those specific to the filesystem type.) Since Linux 2.6.25 auto-destruction of loop devices is supported, meaning that any loop device allocated by mount will be freed by umount independently of /etc/mtab. You can also free a loop device by hand, using losetup -d or umount -d. Since util-linux v2.29, mount re-uses the loop device rather than initializing a new device if the same backing file is already used for some loop device with the same offset and sizelimit. This is necessary to avoid a filesystem corruption. EXIT STATUS top mount has the following exit status values (the bits can be ORed): 0 success 1 incorrect invocation or permissions 2 system error (out of memory, cannot fork, no more loop devices) 4 internal mount bug 8 user interrupt 16 problems writing or locking /etc/mtab 32 mount failure 64 some mount succeeded The command mount -a returns 0 (all succeeded), 32 (all failed), or 64 (some failed, some succeeded). EXTERNAL HELPERS top The syntax of external mount helpers is: /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t type.subtype] where the suffix is the filesystem type and the -sfnvoN options have the same meaning as the normal mount options. The -t option is used for filesystems with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs). The command mount does not pass the mount options unbindable, runbindable, private, rprivate, slave, rslave, shared, rshared, auto, noauto, comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers. All other options are used in a comma-separated list as an argument to the -o option. ENVIRONMENT top LIBMOUNT_FORCE_MOUNT2={always|never|auto} force to use classic mount(2) system call (requires support for new file descriptors based mount API). The default is auto; in this case, libmount tries to be smart and use classic mount(2) only for well-known issues. If the new mount API is unavailable, libmount can still use traditional mount(2), although LIBMOUNT_FORCE_MOUNT2 is set to never. LIBMOUNT_FSTAB=<path> overrides the default location of the fstab file (ignored for suid) LIBMOUNT_DEBUG=all enables libmount debug output LIBBLKID_DEBUG=all enables libblkid debug output LOOPDEV_DEBUG=all enables loop device setup debug output FILES top See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section above. /etc/fstab filesystem table /run/mount libmount private runtime directory /etc/mtab table of mounted filesystems or symlink to /proc/mounts /etc/mtab~ lock file (unused on systems with mtab symlink) /etc/mtab.tmp temporary file (unused on systems with mtab symlink) /etc/filesystems a list of filesystem types to try HISTORY top A mount command existed in Version 5 AT&T UNIX. BUGS top It is possible for a corrupted filesystem to cause a crash. Some Linux filesystems dont support -o sync and -o dirsync (the ext2, ext3, ext4, fat and vfat filesystems do support synchronous updates (a la BSD) when mounted with the sync option). The -o remount may not be able to change mount parameters (all ext2fs-specific parameters, except sb, are changeable with a remount, for example, but you cant change gid or umask for the fatfs). It is possible that the files /etc/mtab and /proc/mounts dont match on systems with a regular mtab file. The first file is based only on the mount command options, but the content of the second file also depends on the kernel and others settings (e.g. on a remote NFS server in certain cases the mount command may report unreliable information about an NFS mount point and the /proc/mount file usually contains more reliable information.) This is another reason to replace the mtab file with a symlink to the /proc/mounts file. Checking files on NFS filesystems referenced by file descriptors (i.e. the fcntl and ioctl families of functions) may lead to inconsistent results due to the lack of a consistency check in the kernel even if the noac mount option is used. The loop option with the offset or sizelimit options used may fail when using older kernels if the mount command cant confirm that the size of the block device has been configured as requested. This situation can be worked around by using the losetup(8) command manually before calling mount with the configured loop device. AUTHORS top Karel Zak <kzak@redhat.com> SEE ALSO top mount(2), umount(2), filesystems(5), fstab(5), nfs(5), xfs(5), mount_namespaces(7), xattr(7), e2label(8), findmnt(8), losetup(8), lsblk(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8), umount(8), xfs_admin(8) REPORTING BUGS top For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY top The mount command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at https://www.kernel.org/pub/linux/utils/util-linux/. If you have a bug report for this manual page, send it to util-linux@vger.kernel.org. This page was obtained from the project's upstream Git repository git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org util-linux 2.39.594-1e0ad 2023-08-25 MOUNT(8) Pages that refer to this page: eject(1), fusermount3(1), homectl(1), mountpoint(1), quotasync(1), systemd-dissect(1), systemd-mount(1), unshare(1), chown(2), fcntl(2), fsync(2), ioctl_iflags(2), mount(2), open(2), open_by_handle_at(2), umount(2), getmntent(3), getsubopt(3), fd(4), hd(4), loop(4), ram(4), autofs(5), ext4(5), filesystems(5), fstab(5), lxc.container.conf(5), nfs(5), nfsmount.conf(5), proc(5), repart.d(5), systemd.automount(5), systemd.exec(5), systemd.mount(5), tmpfs(5), xfs(5), bootparam(7), fanotify(7), file-hierarchy(7), hier(7), inode(7), man-pages(7), mount_namespaces(7), spufs(7), automount(8), blkid(8), btrfs-subvolume(8), e4crypt(8), e4defrag(8), findmnt(8), fsck.cramfs(8), fsck.xfs(8), fsfreeze(8), fstrim(8), lsof(8), mkfs.cramfs(8), mount(8), mount.fuse3(8), mount.nfs(8), pam_namespace(8), pivot_root(8), quotaon(8), swapon(8), switch_root(8), systemd-remount-fs.service(8), tune2fs(8), umount(8), wipefs(8), xfs_admin(8), xfs_db(8), xfs_freeze(8), xfs_growfs(8), xfs_info(8), xfs_logprint(8), xfs_rtcp(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if "~/mnt/sdc1" is mounted Bash Command:<START>mount | grep -q ~/mnt/sdc1<END>

Check if $path_in_question is mount point of filesystem

df $path_in_question | grep " $path_in_question$"

['grep', 'df']

Output a Bash command to accomplish the following task. Task: Check if $path_in_question is mount point of filesystem Bash Command:<START>df $path_in_question | grep " $path_in_question$"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # df\n\n> Display an overview of the filesystem disk space usage.\n> More information: <https://www.gnu.org/software/coreutils/df>.\n\n- Display all filesystems and their disk usage:\n\n`df`\n\n- Display all filesystems and their disk usage in human-readable form:\n\n`df -h`\n\n- Display the filesystem and its disk usage containing the given file or directory:\n\n`df {{path/to/file_or_directory}}`\n\n- Include statistics on the number of free inodes:\n\n`df -i`\n\n- Display filesystems but exclude the specified types:\n\n`df -x {{squashfs}} -x {{tmpfs}}`\n Task: Check if $path_in_question is mount point of filesystem Bash Command:<START>df $path_in_question | grep " $path_in_question$"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. df(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training df(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DF(1) User Commands DF(1) NAME top df - report file system space usage SYNOPSIS top df [OPTION]... [FILE]... DESCRIPTION top This manual page documents the GNU version of df. df displays the amount of space available on the file system containing each file name argument. If no file name is given, the space available on all currently mounted file systems is shown. Space is shown in 1K blocks by default, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. If an argument is the absolute file name of a device node containing a mounted file system, df shows the space available on that file system rather than on the file system containing the device node. This version of df cannot show the space available on unmounted file systems, because on most kinds of systems doing so requires non-portable intimate knowledge of file system structures. OPTIONS top Show information about the file system on which each FILE resides, or all file systems by default. Mandatory arguments to long options are mandatory for short options too. -a, --all include pseudo, duplicate, inaccessible file systems -B, --block-size=SIZE scale sizes by SIZE before printing them; e.g., '-BM' prints sizes in units of 1,048,576 bytes; see SIZE format below -h, --human-readable print sizes in powers of 1024 (e.g., 1023M) -H, --si print sizes in powers of 1000 (e.g., 1.1G) -i, --inodes list inode information instead of block usage -k like --block-size=1K -l, --local limit listing to local file systems --no-sync do not invoke sync before getting usage info (default) --output[=FIELD_LIST] use the output format defined by FIELD_LIST, or print all fields if FIELD_LIST is omitted. -P, --portability use the POSIX output format --sync invoke sync before getting usage info --total elide all entries insignificant to available space, and produce a grand total -t, --type=TYPE limit listing to file systems of type TYPE -T, --print-type print file system type -x, --exclude-type=TYPE limit listing to file systems not of type TYPE -v (ignored) --help display this help and exit --version output version information and exit Display values are in units of the first available SIZE from --block-size, and the DF_BLOCK_SIZE, BLOCK_SIZE and BLOCKSIZE environment variables. Otherwise, units default to 1024 bytes (or 512 if POSIXLY_CORRECT is set). The SIZE argument is an integer and optional unit (example: 10K is 10*1024). Units are K,M,G,T,P,E,Z,Y,R,Q (powers of 1024) or KB,MB,... (powers of 1000). Binary prefixes can be used, too: KiB=K, MiB=M, and so on. FIELD_LIST is a comma-separated list of columns to be included. Valid field names are: 'source', 'fstype', 'itotal', 'iused', 'iavail', 'ipcent', 'size', 'used', 'avail', 'pcent', 'file' and 'target' (see info page). AUTHOR top Written by Torbjorn Granlund, David MacKenzie, and Paul Eggert. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top Full documentation <https://www.gnu.org/software/coreutils/df> or available locally via: info '(coreutils) df invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DF(1) Pages that refer to this page: fstab(5), tmpfs(5), findmnt(8), xfs_quota(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if $path_in_question is mount point of filesystem Bash Command:<START>df $path_in_question | grep " $path_in_question$"<END>

Check if a drive is mounted to nfs

mount |grep nfs

['grep', 'mount']

Output a Bash command to accomplish the following task. Task: Check if a drive is mounted to nfs Bash Command:<START>mount |grep nfs<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # mount\n\n> Provides access to an entire filesystem in one directory.\n> More information: <https://manned.org/mount.8>.\n\n- Show all mounted filesystems:\n\n`mount`\n\n- Mount a device to a directory:\n\n`mount -t {{filesystem_type}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Create a specific directory if it does not exist and mount a device to it:\n\n`mount --mkdir {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a device to a directory for a specific user:\n\n`mount -o uid={{user_id}},gid={{group_id}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a CD-ROM device (with the filetype ISO9660) to `/cdrom` (readonly):\n\n`mount -t {{iso9660}} -o ro {{/dev/cdrom}} {{/cdrom}}`\n\n- Mount all the filesystem defined in `/etc/fstab`:\n\n`mount -a`\n\n- Mount a specific filesystem described in `/etc/fstab` (e.g. `/dev/sda1 /my_drive ext2 defaults 0 2`):\n\n`mount {{/my_drive}}`\n\n- Mount a directory to another directory:\n\n`mount --bind {{path/to/old_dir}} {{path/to/new_dir}}`\n Task: Check if a drive is mounted to nfs Bash Command:<START>mount |grep nfs<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. mount(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training mount(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND-LINE OPTIONS | FILESYSTEM-INDEPENDENT MOUNT OPTIONS | FILESYSTEM-SPECIFIC MOUNT OPTIONS | DM-VERITY SUPPORT | LOOP-DEVICE SUPPORT | EXIT STATUS | EXTERNAL HELPERS | ENVIRONMENT | FILES | HISTORY | BUGS | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY MOUNT(8) System Administration MOUNT(8) NAME top mount - mount a filesystem SYNOPSIS top mount [-h|-V] mount [-l] [-t fstype] mount -a [-fFnrsvw] [-t fstype] [-O optlist] mount [-fnrsvw] [-o options] device|mountpoint mount [-fnrsvw] [-t fstype] [-o options] device mountpoint mount --bind|--rbind|--move olddir newdir mount --make-[shared|slave|private|unbindable|rshared|rslave|rprivate|runbindable] mountpoint DESCRIPTION top All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the filesystem found on some device to the big file tree. Conversely, the umount(8) command will detach it again. The filesystem is used to control how data is stored on the device or provided in a virtual way by network or other services. The standard form of the mount command is: mount -t type device dir This tells the kernel to attach the filesystem found on device (which is of type type) at the directory dir. The option -t type is optional. The mount command is usually able to detect a filesystem. The root permissions are necessary to mount a filesystem by default. See section "Non-superuser mounts" below for more details. The previous contents (if any) and owner and mode of dir become invisible, and as long as this filesystem remains mounted, the pathname dir refers to the root of the filesystem on device. If only the directory or the device is given, for example: mount /dir then mount looks for a mountpoint (and if not found then for a device) in the /etc/fstab file. Its possible to use the --target or --source options to avoid ambiguous interpretation of the given argument. For example: mount --target /mountpoint The same filesystem may be mounted more than once, and in some cases (e.g., network filesystems) the same filesystem may be mounted on the same mountpoint multiple times. The mount command does not implement any policy to control this behavior. All behavior is controlled by the kernel and it is usually specific to the filesystem driver. The exception is --all, in this case already mounted filesystems are ignored (see --all below for more details). Listing the mounts The listing mode is maintained for backward compatibility only. For more robust and customizable output use findmnt(8), especially in your scripts. Note that control characters in the mountpoint name are replaced with '?'. The following command lists all mounted filesystems (of type type): mount [-l] [-t type] The option -l adds labels to this listing. See below. Indicating the device and filesystem Most devices are indicated by a filename (of a block special device), like /dev/sda1, but there are other possibilities. For example, in the case of an NFS mount, device may look like knuth.cwi.nl:/dir. The device names of disk partitions are unstable; hardware reconfiguration, and adding or removing a device can cause changes in names. This is the reason why its strongly recommended to use filesystem or partition identifiers like UUID or LABEL. Currently supported identifiers (tags): LABEL=label Human readable filesystem identifier. See also -L. UUID=uuid Filesystem universally unique identifier. The format of the UUID is usually a series of hex digits separated by hyphens. See also -U. Note that mount uses UUIDs as strings. The UUIDs from the command line or from fstab(5) are not converted to internal binary representation. The string representation of the UUID should be based on lower case characters. PARTLABEL=label Human readable partition identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). PARTUUID=uuid Partition universally unique identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). ID=id Hardware block device ID as generated by udevd. This identifier is usually based on WWN (unique storage identifier) and assigned by the hardware manufacturer. See ls /dev/disk/by-id for more details, this directory and running udevd is required. This identifier is not recommended for generic use as the identifier is not strictly defined and it depends on udev, udev rules and hardware. The command lsblk --fs provides an overview of filesystems, LABELs and UUIDs on available block devices. The command blkid -p <device> provides details about a filesystem on the specified device. Dont forget that there is no guarantee that UUIDs and labels are really unique, especially if you move, share or copy the device. Use lsblk -o +UUID,PARTUUID to verify that the UUIDs are really unique in your system. The recommended setup is to use tags (e.g. UUID=uuid) rather than /dev/disk/by-{label,uuid,id,partuuid,partlabel} udev symlinks in the /etc/fstab file. Tags are more readable, robust and portable. The mount(8) command internally uses udev symlinks, so the use of symlinks in /etc/fstab has no advantage over tags. For more details see libblkid(3). The proc filesystem is not associated with a special device, and when mounting it, an arbitrary keyword - for example, proc - can be used instead of a device specification. (The customary choice none is less fortunate: the error message 'none already mounted' from mount can be confusing.) The files /etc/fstab, /etc/mtab and /proc/mounts The file /etc/fstab (see fstab(5)), may contain lines describing what devices are usually mounted where, using which options. The default location of the fstab(5) file can be overridden with the --fstab path command-line option (see below for more details). The command mount -a [-t type] [-O optlist] (usually given in a bootscript) causes all filesystems mentioned in fstab (of the proper type and/or having or not having the proper options) to be mounted as indicated, except for those whose line contains the noauto keyword. Adding the -F option will make mount fork, so that the filesystems are mounted in parallel. When mounting a filesystem mentioned in fstab or mtab, it suffices to specify on the command line only the device, or only the mount point. The programs mount and umount(8) traditionally maintained a list of currently mounted filesystems in the file /etc/mtab. The support for regular classic /etc/mtab is completely disabled at compile time by default, because on current Linux systems it is better to make /etc/mtab a symlink to /proc/mounts instead. The regular mtab file maintained in userspace cannot reliably work with namespaces, containers and other advanced Linux features. If the regular mtab support is enabled, then its possible to use the file as well as the symlink. If no arguments are given to mount, the list of mounted filesystems is printed. If you want to override mount options from /etc/fstab, you have to use the -o option: mount device|dir -o options and then the mount options from the command line will be appended to the list of options from /etc/fstab. This default behaviour can be changed using the --options-mode command-line option. The usual behavior is that the last option wins if there are conflicting ones. The mount program does not read the /etc/fstab file if both device (or LABEL, UUID, ID, PARTUUID or PARTLABEL) and dir are specified. For example, to mount device foo at /dir: mount /dev/foo /dir This default behaviour can be changed by using the --options-source-force command-line option to always read configuration from fstab. For non-root users mount always reads the fstab configuration. Non-superuser mounts Normally, only the superuser can mount filesystems. However, when fstab contains the user option on a line, anybody can mount the corresponding filesystem. Thus, given a line /dev/cdrom /cd iso9660 ro,user,noauto,unhide any user can mount the iso9660 filesystem found on an inserted CDROM using the command: mount /cd Note that mount is very strict about non-root users and all paths specified on command line are verified before fstab is parsed or a helper program is executed. Its strongly recommended to use a valid mountpoint to specify filesystem, otherwise mount may fail. For example its a bad idea to use NFS or CIFS source on command line. Since util-linux 2.35, mount does not exit when user permissions are inadequate according to libmounts internal security rules. Instead, it drops suid permissions and continues as regular non-root user. This behavior supports use-cases where root permissions are not necessary (e.g., fuse filesystems, user namespaces, etc). For more details, see fstab(5). Only the user that mounted a filesystem can unmount it again. If any user should be able to unmount it, then use users instead of user in the fstab line. The owner option is similar to the user option, with the restriction that the user must be the owner of the special file. This may be useful e.g. for /dev/fd if a login script makes the console user owner of this device. The group option is similar, with the restriction that the user must be a member of the group of the special file. The user mount option is accepted if no username is specified. If used in the format user=someone, the option is silently ignored and visible only for external mount helpers (/sbin/mount.<type>) for compatibility with some network filesystems. Bind mount operation Remount part of the file hierarchy somewhere else. The call is: mount --bind olddir newdir or by using this fstab entry: /olddir /newdir none bind After this call the same contents are accessible in two places. It is important to understand that "bind" does not create any second-class or special node in the kernel VFS. The "bind" is just another operation to attach a filesystem. There is nowhere stored information that the filesystem has been attached by a "bind" operation. The olddir and newdir are independent and the olddir may be unmounted. One can also remount a single file (on a single file). Its also possible to use a bind mount to create a mountpoint from a regular directory, for example: mount --bind foo foo The bind mount call attaches only (part of) a single filesystem, not possible submounts. The entire file hierarchy including submounts can be attached a second place by using: mount --rbind olddir newdir Note that the filesystem mount options maintained by the kernel will remain the same as those on the original mount point. The userspace mount options (e.g., _netdev) will not be copied by mount and its necessary to explicitly specify the options on the mount command line. Since util-linux 2.27 mount permits changing the mount options by passing the relevant options along with --bind. For example: mount -o bind,ro foo foo This feature is not supported by the Linux kernel; it is implemented in userspace by an additional mount(2) remounting system call. This solution is not atomic. The alternative (classic) way to create a read-only bind mount is to use the remount operation, for example: mount --bind olddir newdir mount -o remount,bind,ro olddir newdir Note that a read-only bind will create a read-only mountpoint (VFS entry), but the original filesystem superblock will still be writable, meaning that the olddir will be writable, but the newdir will be read-only. Its also possible to change nosuid, nodev, noexec, noatime, nodiratime, relatime and nosymfollow VFS entry flags via a "remount,bind" operation. The other flags (for example filesystem-specific flags) are silently ignored. The classic mount(2) system call does not allow to change mount options recursively (for example with -o rbind,ro). The recursive semantic is possible with a new mount_setattr(2) kernel system call and its supported since libmount from util-linux v2.39 by a new experimental "recursive" option argument (e.g. -o rbind,ro=recursive). For more details see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS section. Since util-linux 2.31, mount ignores the bind flag from /etc/fstab on a remount operation (if -o remount is specified on command line). This is necessary to fully control mount options on remount by command line. In previous versions the bind flag has been always applied and it was impossible to re-define mount options without interaction with the bind semantic. This mount behavior does not affect situations when "remount,bind" is specified in the /etc/fstab file. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink. This feature is usable (only) with the new kernel mount API where bind mount over symlinks is supported. The move operation Move a mounted tree to another place (atomically). The call is: mount --move olddir newdir This will cause the contents which previously appeared under olddir to now be accessible under newdir. The physical location of the files is not changed. Note that olddir has to be a mountpoint. Note also that moving a mount residing under a shared mount is invalid and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current propagation flags. Shared subtree operations Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, private, slave or unbindable. A shared mount provides the ability to create mirrors of that mount such that mounts and unmounts within any of the mirrors propagate to the other mirror. A slave mount receives propagation from its master, but not vice versa. A private mount carries no propagation abilities. An unbindable mount is a private mount which cannot be cloned through a bind operation. The detailed semantics are documented in Documentation/filesystems/sharedsubtree.txt file in the kernel source tree; see also mount_namespaces(7). Supported operations are: mount --make-shared mountpoint mount --make-slave mountpoint mount --make-private mountpoint mount --make-unbindable mountpoint The following commands allow one to recursively change the type of all the mounts under a given mountpoint. mount --make-rshared mountpoint mount --make-rslave mountpoint mount --make-rprivate mountpoint mount --make-runbindable mountpoint mount does not read fstab(5) when a --make-* operation is requested. All necessary information has to be specified on the command line. Note that the Linux kernel does not allow changing multiple propagation flags with a single mount(2) system call, and the flags cannot be mixed with other mount options and operations. Since util-linux 2.23 the mount command can be used to do more propagation (topology) changes by one mount(8) call and do it also together with other mount operations. The propagation flags are applied by additional mount(2) system calls when the preceding mount operations were successful. Note that this use case is not atomic. It is possible to specify the propagation flags in fstab(5) as mount options (private, slave, shared, unbindable, rprivate, rslave, rshared, runbindable). For example: mount --make-private --make-unbindable /dev/sda1 /foo is the same as: mount /dev/sda1 /foo mount --make-private /foo mount --make-unbindable /foo COMMAND-LINE OPTIONS top The full set of mount options used by an invocation of mount is determined by first extracting the mount options for the filesystem from the fstab table, then applying any options specified by the -o argument, and finally applying a -r or -w option, when present. The mount command does not pass all command-line options to the /sbin/mount.suffix mount helpers. The interface between mount and the mount helpers is described below in the EXTERNAL HELPERS section. Command-line options available for the mount command are: -a, --all Mount all filesystems (of the given types) mentioned in fstab (except for those whose line contains the noauto keyword). The filesystems are mounted following their order in fstab. The mount command compares filesystem source, target (and fs root for bind mount or btrfs) to detect already mounted filesystems. The kernel table with already mounted filesystems is cached during mount --all. This means that all duplicated fstab entries will be mounted. The correct functionality depends on /proc (to detect already mounted filesystems) and on /sys (to evaluate filesystem tags like UUID= or LABEL=). Its strongly recommended to mount /proc and /sys filesystems before mount -a is executed, or keep /proc and /sys at the beginning of fstab. The option --all is possible to use for remount operation too. In this case all filters (-t and -O) are applied to the table of already mounted filesystems. Since version 2.35 it is possible to use the command line option -o to alter mount options from fstab (see also --options-mode). Note that it is a bad practice to use mount -a for fstab checking. The recommended solution is findmnt --verify. -B, --bind Remount a subtree somewhere else (so that its contents are available in both places). See above, under Bind mount operation. -c, --no-canonicalize Dont canonicalize paths. The mount command canonicalizes all paths (from the command line or fstab) by default. The option is designed for mount helpers which call mount -i. It is strongly recommended to not use this command-line option for normal mount operations. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink (see "Bind mount operation" section for more details). Note that mount does not pass this option to the /sbin/mount.type helpers. -F, --fork (Used in conjunction with -a.) Fork off a new incarnation of mount for each device. This will do the mounts on different devices or different NFS servers in parallel. This has the advantage that it is faster; also NFS timeouts proceed in parallel. A disadvantage is that the order of the mount operations is undefined. Thus, you cannot use this option if you want to mount both /usr and /usr/spool. -f, --fake Causes everything to be done except for the mount-related system calls. The --fake option was originally designed to write an entry to /etc/mtab without actually mounting. The /etc/mtab is no longer maintained in userspace, and starting from version 2.39, the mount operation can be a complex chain of operations with dependencies between the syscalls. The --fake option forces libmount to skip all mount source preparation, mount option analysis, and the actual mounting process. The difference between fake and non-fake execution is huge. This is the reason why the --fake option has minimal significance for the current mount(8) implementation and it is maintained mostly for backward compatibility. -i, --internal-only Dont call the /sbin/mount.filesystem helper even if it exists. -L, --label label Mount the partition that has the specified label. -l, --show-labels Add the labels in the mount output. mount must have permission to read the disk device (e.g. be set-user-ID root) for this to work. One can set such a label for ext2, ext3 or ext4 using the e2label(8) utility, or for XFS using xfs_admin(8), or for reiserfs using reiserfstune(8). -M, --move Move a subtree to some other place. See above, the subsection The move operation. -m, --mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. Alias to "-o X-mount.mkdir[=mode]", the default mode is 0755. For more details see X-mount.mkdir below. --map-groups, --map-users inner:_outer_:_count_ Add the specified user/group mapping to an X-mount.idmap map. These options can be given multiple times to build up complete mappings for users and groups. For more details see X-mount.idmap below. --map-users /proc/PID/ns/user Use the specified user namespace for user and group mapping in an id-mapped mount. This is an alias for "-o X-mount.idmap=/proc/PID/ns/user" and cannot be used twice nor together with the inner:_outer_:_count_ option format above. For more details see X-mount.idmap below. -n, --no-mtab Mount without writing in /etc/mtab. This is necessary for example when /etc is on a read-only filesystem. -N, --namespace ns Perform the mount operation in the mount namespace specified by ns. ns is either PID of process running in that namespace or special file representing that namespace. mount switches to the mount namespace when it reads /etc/fstab, writes /etc/mtab: (or writes to _/run/mount) and calls mount(2), otherwise it runs in the original mount namespace. This means that the target namespace does not have to contain any libraries or other requirements necessary to execute the mount(2) call. See mount_namespaces(7) for more information. -O, --test-opts opts Limit the set of filesystems to which the -a option applies. In this regard it is like the -t option except that -O is useless without -a. For example, the command mount -a -O no_netdev mounts all filesystems except those which have the option netdev specified in the options field in the /etc/fstab file. It is different from -t in that each option is matched exactly; a leading no at the beginning of one option does not negate the rest. The -t and -O options are cumulative in effect; that is, the command mount -a -t ext2 -O _netdev mounts all ext2 filesystems with the _netdev option, not all filesystems that are either ext2 or have the _netdev option specified. -o, --options opts Use the specified mount options. The opts argument is a comma-separated list. For example: mount LABEL=mydisk -o noatime,nodev,nosuid Note that the order of the options matters, as the last option wins if there are conflicting ones. The options from the command line also overwrite options from fstab by default. For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections. --onlyonce Forces mount command to check if the filesystem is already mounted. This behavior is the default for --all; otherwise, it depends on the kernel filesystem driver. Some filesystems may be mounted more than once on the same mount point (e.g. tmpfs). --options-mode mode Controls how to combine options from fstab/mtab with options from the command line. mode can be one of ignore, append, prepend or replace. For example, append means that options from fstab are appended to options from the command line. The default value is prepend it means command line options are evaluated after fstab options. Note that the last option wins if there are conflicting ones. --options-source source Source of default options. source is a comma-separated list of fstab, mtab and disable. disable disables fstab and mtab and enables --options-source-force. The default value is fstab,mtab. --options-source-force Use options from fstab/mtab even if both device and dir are specified. -R, --rbind Remount a subtree and all possible submounts somewhere else (so that its contents are available in both places). See above, the subsection Bind mount operation. -r, --read-only Mount the filesystem read-only. A synonym is -o ro. Note that, depending on the filesystem type, state and kernel behavior, the system may still write to the device. For example, ext3 and ext4 will replay the journal if the filesystem is dirty. To prevent this kind of write access, you may want to mount an ext3 or ext4 filesystem with the ro,noload mount options or set the block device itself to read-only mode, see the blockdev(8) command. -s Tolerate sloppy mount options rather than failing. This will ignore mount options not supported by a filesystem type. Not all filesystems support this option. Currently its supported by the mount.nfs mount helper only. --source device If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount source. --target directory If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount target. --target-prefix directory Prepend the specified directory to all mount targets. This option can be used to follow fstab, but mount operations are done in another place, for example: mount --all --target-prefix /chroot -o X-mount.mkdir mounts all from system fstab to /chroot, all missing mountpoint are created (due to X-mount.mkdir). See also --fstab to use an alternative fstab. -T, --fstab path Specifies an alternative fstab file. If path is a directory, then the files in the directory are sorted by strverscmp(3); files that start with "." or without an .fstab extension are ignored. The option can be specified more than once. This option is mostly designed for initramfs or chroot scripts where additional configuration is specified beyond standard system configuration. Note that mount does not pass the option --fstab to the /sbin/mount.type helpers, meaning that the alternative fstab files will be invisible for the helpers. This is no problem for normal mounts, but user (non-root) mounts always require fstab to verify the users rights. -t, --types fstype The argument following the -t is used to indicate the filesystem type. The filesystem types which are currently supported depend on the running kernel. See /proc/filesystems and /lib/modules/$(uname -r)/kernel/fs for a complete list of the filesystems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs. The programs mount and umount(8) support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For example 'fuse.sshfs'. Its recommended to use subtype notation rather than add any prefix to the mount source (for example 'sshfs#example.com' is deprecated). If no -t option is given, or if the auto type is specified, mount will try to guess the desired type. mount uses the libblkid(3) library for guessing the filesystem type; if that does not turn up anything that looks familiar, mount will try to read the file /etc/filesystems, or, if that does not exist, /proc/filesystems. All of the filesystem types listed there will be tried, except for those that are labeled "nodev" (e.g. devpts, proc and nfs). If /etc/filesystems ends in a line with a single *, mount will read /proc/filesystems afterwards. While trying, all filesystem types will be mounted with the mount option silent. The auto type may be useful for user-mounted floppies. Creating a file /etc/filesystems can be useful to change the probe order (e.g., to try vfat before msdos or ext3 before ext2) or if you use a kernel module autoloader. More than one type may be specified in a comma-separated list, for the -t option as well as in an /etc/fstab entry. The list of filesystem types for the -t option can be prefixed with no to specify the filesystem types on which no action should be taken. The prefix no has no effect when specified in an /etc/fstab entry. The prefix no can be meaningful with the -a option. For example, the command mount -a -t nomsdos,smbfs mounts all filesystems except those of type msdos and smbfs. For most types all the mount program has to do is issue a simple mount(2) system call, and no detailed knowledge of the filesystem type is required. For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems have a separate mount program. In order to make it possible to treat all types in a uniform way, mount will execute the program /sbin/mount.type (if that exists) when called with type type. Since different versions of the smbmount program have different calling conventions, /sbin/mount.smbfs may have to be a shell script that sets up the desired call. -U, --uuid uuid Mount the partition that has the specified uuid. -v, --verbose Verbose mode. -w, --rw, --read-write Mount the filesystem read/write. Read-write is the kernel default and the mount default is to try read-only if the previous mount(2) syscall with read-write flags on write-protected devices failed. A synonym is -o rw. Note that specifying -w on the command line forces mount to never try read-only mount on write-protected devices or already mounted read-only filesystems. -h, --help Display help text and exit. -V, --version Print version and exit. FILESYSTEM-INDEPENDENT MOUNT OPTIONS top Some of these options are only useful when they appear in the /etc/fstab file. Some of these options could be enabled or disabled by default in the system kernel. To check the current setting see the options in /proc/mounts. Note that filesystems also have per-filesystem specific default mount options (see for example tune2fs -l output for extN filesystems). The options nosuid, noexec, nodiratime, relatime, noatime, strictatime, and nosymfollow are interpreted only by the abstract VFS kernel layer and applied to the mountpoint node rather than to the filesystem itself. Try: findmnt -o TARGET,VFS-OPTIONS,FS-OPTIONS to get a complete overview of filesystems and VFS options. The read-only setting (ro or rw) is interpreted by VFS and the filesystem and depends on how the option is specified on the mount(8) command line. The default is to interpret it on the filesystem level. The operation "-o bind,remount,ro" is applied only to the VFS mountpoint, and operation "-o remount,ro" is applied to VFS and filesystem superblock. This semantic allows create a read-only mountpoint but keeps the filesystem writable from another mountpoint. Since v2.39 libmount can use a new kernel mount interface to set the VFS options recursive. For backward compatibility, this feature is not enabled by default, although recursive operation (e.g. rbind) has been requested. The new option argument "recursive" could be specified, for example: mount -orbind,ro=recursive,noexec=recursive,nosuid /foo /bar recursively binds filesystems from /foo to /bar, /bar, and all submounts will be read-only and noexec, but only /bar itself will be "nosuid". The "recursive" optional argument for VFS mount options is an EXPERIMENTAL feature. The following options apply to any filesystem that is being mounted (but not every filesystem actually honors them - e.g., the sync option today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs): async All I/O to the filesystem should be done asynchronously. (See also the sync option.) atime Do not use the noatime feature, so the inode access time is controlled by kernel defaults. See also the descriptions of the relatime and strictatime mount options. noatime Do not update inode access times on this filesystem (e.g. for faster access on the news spool to speed up news servers). This works for all inode types (directories too), so it implies nodiratime. auto Can be mounted with the -a option. noauto Can only be mounted explicitly (i.e., the -a option will not cause the filesystem to be mounted). context=context, fscontext=context, defcontext=context, and rootcontext=context The context= option is useful when mounting filesystems that do not support extended attributes, such as a floppy or hard disk formatted with VFAT, or systems that are not normally running under SELinux, such as an ext3 or ext4 formatted disk from a non-SELinux workstation. You can also use context= on filesystems you do not trust, such as a floppy. It also helps in compatibility with xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where xattrs are supported, you can save time not having to label every file by assigning the entire disk one security context. A commonly used option for removable media is context="system_u:object_r:removable_t. The fscontext= option works for all filesystems, regardless of their xattr support. The fscontext option sets the overarching filesystem label to a specific security context. This filesystem label is separate from the individual labels on the files. It represents the entire filesystem for certain kinds of permission checks, such as during mount or file creation. Individual file labels are still obtained from the xattrs on the files themselves. The context option actually sets the aggregate context that fscontext provides, in addition to supplying the same label for individual files. You can set the default security context for unlabeled files using defcontext= option. This overrides the value set for unlabeled files in the policy and requires a filesystem that supports xattr labeling. The rootcontext= option allows you to explicitly label the root inode of a FS being mounted before that FS or inode becomes visible to userspace. This was found to be useful for things like stateless Linux. The special value @target can be used to assign the current context of the target mountpoint location. Note that the kernel rejects any remount request that includes the context option, even when unchanged from the current context. Warning: the context value might contain commas, in which case the value has to be properly quoted, otherwise mount will interpret the comma as a separator between mount options. Dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t tmpfs none /mnt -o \ 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec' For more details, see selinux(8). defaults Use the default options: rw, suid, dev, exec, auto, nouser, and async. Note that the real set of all default mount options depends on the kernel and filesystem type. See the beginning of this section for more details. dev Interpret character or block special devices on the filesystem. nodev Do not interpret character or block special devices on the filesystem. diratime Update directory inode access times on this filesystem. This is the default. (This option is ignored when noatime is set.) nodiratime Do not update directory inode access times on this filesystem. (This option is implied when noatime is set.) dirsync All directory updates within the filesystem should be done synchronously. This affects the following system calls: creat(2), link(2), unlink(2), symlink(2), mkdir(2), rmdir(2), mknod(2) and rename(2). exec Permit execution of binaries and other executable files. noexec Do not permit direct execution of any binaries on the mounted filesystem. group Allow an ordinary user to mount the filesystem if one of that users groups matches the group of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line group,dev,suid). iversion Every time the inode is modified, the i_version field will be incremented. noiversion Do not increment the i_version inode field. mand Allow mandatory locks on this filesystem. See fcntl(2). This option was deprecated in Linux 5.15. nomand Do not allow mandatory locks on this filesystem. _netdev The filesystem resides on a device that requires network access (used to prevent the system from attempting to mount these filesystems until the network has been enabled on the system). nofail Do not report errors for this device if it does not exist. relatime Update inode access times relative to modify or change time. Access time is only updated if the previous access time was earlier than or equal to the current modify or change time. (Similar to noatime, but it doesnt break mutt(1) or other applications that need to know if a file has been read since the last time it was modified.) Since Linux 2.6.30, the kernel defaults to the behavior provided by this option (unless noatime was specified), and the strictatime option is required to obtain traditional semantics. In addition, since Linux 2.6.30, the files last access time is always updated if it is more than 1 day old. norelatime Do not use the relatime feature. See also the strictatime mount option. strictatime Allows to explicitly request full atime updates. This makes it possible for the kernel to default to relatime or noatime but still allow userspace to override it. For more details about the default system mount options see /proc/mounts. nostrictatime Use the kernels default behavior for inode access time updates. lazytime Only update times (atime, mtime, ctime) on the in-memory version of the file inode. This mount option significantly reduces writes to the inode table for workloads that perform frequent random writes to preallocated files. The on-disk timestamps are updated only when: the inode needs to be updated for some change unrelated to file timestamps the application employs fsync(2), syncfs(2), or sync(2) an undeleted inode is evicted from memory more than 24 hours have passed since the inode was written to disk. nolazytime Do not use the lazytime feature. suid Honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. nosuid Do not honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. In addition, SELinux domain transitions require permission nosuid_transition, which in turn needs also policy capability nnp_nosuid_transition. silent Turn on the silent flag. loud Turn off the silent flag. owner Allow an ordinary user to mount the filesystem if that user is the owner of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line owner,dev,suid). remount Attempt to remount an already-mounted filesystem. This is commonly used to change the mount flags for a filesystem, especially to make a readonly filesystem writable. It does not change device or mount point. The remount operation together with the bind flag has special semantics. See above, the subsection Bind mount operation. The default kernel behavior for VFS mount flags (nodev,nosuid,noexec,ro) is to reset all unspecified flags on remount. Thats why mount(8) tries to keep the current setting according to fstab or /proc/self/mountinfo. This default behavior is possible to change by --options-mode. The recursive change of the mount flags (supported since v2.39 on systems with mount_setattr(2) syscall), for example, mount -o remount,ro=recursive, do not use "reset-unspecified" behavior, and it works as a simple add/remove operation and unspecified flags are not modified. The remount functionality follows the standard way the mount command works with options from fstab. This means that mount does not read fstab (or mtab) only when both device and dir are specified. mount -o remount,rw /dev/foo /dir After this call all old mount options are replaced and arbitrary stuff from fstab (or mtab) is ignored, except the loop= option which is internally generated and maintained by the mount command. mount -o remount,rw /dir After this call, mount reads fstab and merges these options with the options from the command line (-o). If no mountpoint is found in fstab, then it defaults to mount options from /proc/self/mountinfo. mount allows the use of --all to remount all already mounted filesystems which match a specified filter (-O and -t). For example: mount --all -o remount,ro -t vfat remounts all already mounted vfat filesystems in read-only mode. Each of the filesystems is remounted by mount -o remount,ro /dir semantic. This means the mount command reads fstab or mtab and merges these options with the options from the command line. ro Mount the filesystem read-only. rw Mount the filesystem read-write. sync All I/O to the filesystem should be done synchronously. In the case of media with a limited number of write cycles (e.g. some flash drives), sync may cause life-cycle shortening. user Allow an ordinary user to mount the filesystem. The name of the mounting user is written to the mtab file (or to the private libmount file in /run/mount on systems without a regular mtab) so that this same user can unmount the filesystem again. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line user,exec,dev,suid). nouser Forbid an ordinary user to mount the filesystem. This is the default; it does not imply any other options. users Allow any user to mount and to unmount the filesystem, even when some other ordinary user mounted it. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line users,exec,dev,suid). X-* All options prefixed with "X-" are interpreted as comments or as userspace application-specific options. These options are not stored in user space (e.g., mtab file), nor sent to the mount.type helpers nor to the mount(2) system call. The suggested format is X-appname.option. x-* The same as X-* options, but stored permanently in user space. This means the options are also available for umount(8) or other operations. Note that maintaining mount options in user space is tricky, because its necessary use libmount-based tools and there is no guarantee that the options will be always available (for example after a move mount operation or in unshared namespace). Note that before util-linux v2.30 the x-* options have not been maintained by libmount and stored in user space (functionality was the same as for X-* now), but due to the growing number of use-cases (in initrd, systemd etc.) the functionality has been extended to keep existing fstab configurations usable without a change. X-mount.auto-fstypes=list Specifies allowed or forbidden filesystem types for automatic filesystem detection. The list is a comma-separated list of the filesystem names. The automatic filesystem detection is triggered by the "auto" filesystem type or when the filesystem type is not specified. Thy list follows how mount evaluates type patterns (see -t for more details). Only specified filesystem types are allowed, or all specified types are forbidden if the list is prefixed by "no". For example, X-mount.auto-fstypes="ext4,btrfs" accepts only ext4 and btrfs, and X-mount.auto-fstypes="novfat,xfs" accepts all filesystems except vfat and xfs. Note that comma is used as a separator between mount options, it means that auto-fstypes values have to be properly quoted, dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t auto -oX-mount.auto-fstypes="noext2,ext3"' /dev/sdc1 /mnt/test X-mount.mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. The optional argument mode specifies the filesystem access mode used for mkdir(2) in octal notation. The default mode is 0755. This functionality is supported only for root users or when mount is executed without suid permissions. The option is also supported as x-mount.mkdir, but this notation is deprecated since v2.30. See also --mkdir command line option. X-mount.subdir=directory Allow mounting sub-directory from a filesystem instead of the root directory. For now, this feature is implemented by temporary filesystem root directory mount in unshared namespace and then bind the sub-directory to the final mount point and umount the root of the filesystem. The sub-directory mount shows up atomically for the rest of the system although it is implemented by multiple mount(2) syscalls. Note that this feature will not work in session with an unshared private mount namespace (after unshare --mount) on old kernels or with mount(8) without support for file-descriptors-based mount kernel API. In this case, you need unshare --mount --propagation shared. This feature is EXPERIMENTAL. X-mount.owner=username|UID, X-mount.group=group|GID Set mountpoint's ownership after mounting. Names resolved in the target mount namespace, see -N. X-mount.mode=mode Set mountpoint's mode after mounting. X-mount.idmap=id-type:id-mount:id-host:id-range [id-type:id-mount:id-host:id-range], X-mount.idmap=file Use this option to create an idmapped mount. An idmapped mount allows to change ownership of all files located under a mount according to the ID-mapping associated with a user namespace. The ownership change is tied to the lifetime and localized to the relevant mount. The relevant ID-mapping can be specified in two ways: A user can specify the ID-mapping directly. The ID-mapping must be specified using the syntax id-type:id-mount:id-host:id-range. Specifying u as the id-type prefix creates a UID-mapping, g creates a GID-mapping and omitting id-type or specifying b creates both a UID- and GID-mapping. The id-mount parameter indicates the starting ID in the new mount. The id-host parameter indicates the starting ID in the filesystem. The id-range parameter indicates how many IDs are to be mapped. It is possible to specify multiple ID-mappings. The individual ID-mappings must be separated by spaces. For example, the ID-mapping X-mount.idmap=u:1000:0:1 g:1001:1:2 5000:1000:2 creates an idmapped mount where UID 0 is mapped to UID 1000, GID 1 is mapped to GUID 1001, GID 2 is mapped to GID 1002, UID and GID 1000 are mapped to 5000, and UID and GID 1001 are mapped to 5001 in the mount. When an ID-mapping is specified directly a new user namespace will be allocated with the requested ID-mapping. The newly created user namespace will be attached to the mount. A user can specify a user namespace file. The user namespace will then be attached to the mount and the ID-mapping of the user namespace will become the ID-mapping of the mount. For example, X-mount.idmap=/proc/PID/ns/user will attach the user namespace of the process PID to the mount. nosymfollow Do not follow symlinks when resolving paths. Symlinks can still be created, and readlink(1), readlink(2), realpath(1), and realpath(3) all still work properly. FILESYSTEM-SPECIFIC MOUNT OPTIONS top This section lists options that are specific to particular filesystems. Where possible, you should first consult filesystem-specific manual pages for details. Some of those pages are listed in the following table. Filesystem(s) Manual page btrfs btrfs(5) cifs mount.cifs(8) ext2, ext3, ext4 ext4(5) fuse fuse(8) nfs nfs(5) tmpfs tmpfs(5) xfs xfs(5) Note that some of the pages listed above might be available only after you install the respective userland tools. The following options apply only to certain filesystems. We sort them by filesystem. All options follow the -o flag. What options are supported depends a bit on the running kernel. Further information may be available in filesystem-specific files in the kernel source subdirectory Documentation/filesystems. Mount options for adfs uid=value and gid=value Set the owner and group of the files in the filesystem (default: uid=gid=0). ownmask=value and othmask=value Set the permission mask for ADFS 'owner' permissions and 'other' permissions, respectively (default: 0700 and 0077, respectively). See also /usr/src/linux/Documentation/filesystems/adfs.rst. Mount options for affs uid=value and gid=value Set the owner and group of the root of the filesystem (default: uid=gid=0, but with option uid or gid without specified value, the UID and GID of the current process are taken). setuid=value and setgid=value Set the owner and group of all files. mode=value Set the mode of all files to value & 0777 disregarding the original permissions. Add search permission to directories that have read permission. The value is given in octal. protect Do not allow any changes to the protection bits on the filesystem. usemp Set UID and GID of the root of the filesystem to the UID and GID of the mount point upon the first sync or umount, and then clear this option. Strange... verbose Print an informational message for each successful mount. prefix=string Prefix used before volume name, when following a link. volume=string Prefix (of length at most 30) used before '/' when following a symbolic link. reserved=value (Default: 2.) Number of unused blocks at the start of the device. root=value Give explicitly the location of the root block. bs=value Give blocksize. Allowed values are 512, 1024, 2048, 4096. grpquota|noquota|quota|usrquota These options are accepted but ignored. (However, quota utilities may react to such strings in /etc/fstab.) Mount options for debugfs The debugfs filesystem is a pseudo filesystem, traditionally mounted on /sys/kernel/debug. As of kernel version 3.4, debugfs has the following options: uid=n, gid=n Set the owner and group of the mountpoint. mode=value Sets the mode of the mountpoint. Mount options for devpts The devpts filesystem is a pseudo filesystem, traditionally mounted on /dev/pts. In order to acquire a pseudo terminal, a process opens /dev/ptmx; the number of the pseudo terminal is then made available to the process and the pseudo terminal slave can be accessed as /dev/pts/<number>. uid=value and gid=value This sets the owner or the group of newly created pseudo terminals to the specified values. When nothing is specified, they will be set to the UID and GID of the creating process. For example, if there is a tty group with GID 5, then gid=5 will cause newly created pseudo terminals to belong to the tty group. mode=value Set the mode of newly created pseudo terminals to the specified value. The default is 0600. A value of mode=620 and gid=5 makes "mesg y" the default on newly created pseudo terminals. newinstance Create a private instance of the devpts filesystem, such that indices of pseudo terminals allocated in this new instance are independent of indices created in other instances of devpts. All mounts of devpts without this newinstance option share the same set of pseudo terminal indices (i.e., legacy mode). Each mount of devpts with the newinstance option has a private set of pseudo terminal indices. This option is mainly used to support containers in the Linux kernel. It is implemented in Linux kernel versions starting with 2.6.29. Further, this mount option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. To use this option effectively, /dev/ptmx must be a symbolic link to pts/ptmx. See Documentation/filesystems/devpts.txt in the Linux kernel source tree for details. ptmxmode=value Set the mode for the new ptmx device node in the devpts filesystem. With the support for multiple instances of devpts (see newinstance option above), each instance has a private ptmx node in the root of the devpts filesystem (typically /dev/pts/ptmx). For compatibility with older versions of the kernel, the default mode of the new ptmx node is 0000. ptmxmode=value specifies a more useful mode for the ptmx node and is highly recommended when the newinstance option is specified. This option is only implemented in Linux kernel versions starting with 2.6.29. Further, this option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. Mount options for fat (Note: fat is not a separate filesystem, but a common part of the msdos, umsdos and vfat filesystems.) blocksize={512|1024|2048} Set blocksize (default 512). This option is obsolete. uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. dmask=value Set the umask applied to directories only. The default is the umask of the current process. The value is given in octal. fmask=value Set the umask applied to regular files only. The default is the umask of the current process. The value is given in octal. allow_utime=value This option controls the permission check of mtime/atime. 20 If current process is in group of files group ID, you can change timestamp. 2 Other users can change timestamp. The default is set from 'dmask' option. (If the directory is writable, utime(2) is also allowed. I.e. ~dmask & 022) Normally utime(2) checks that the current process is owner of the file, or that it has the CAP_FOWNER capability. But FAT filesystems dont have UID/GID on disk, so the normal check is too inflexible. With this option you can relax it. check=value Three different levels of pickiness can be chosen: r[elaxed] Upper and lower case are accepted and equivalent, long name parts are truncated (e.g. verylongname.foobar becomes verylong.foo), leading and embedded spaces are accepted in each name part (name and extension). n[ormal] Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are rejected. This is the default. s[trict] Like "normal", but names that contain long parts or special characters that are sometimes used on Linux but are not accepted by MS-DOS (+, =, etc.) are rejected. codepage=value Sets the codepage for converting to shortname characters on FAT and VFAT filesystems. By default, codepage 437 is used. conv=mode This option is obsolete and may fail or be ignored. cvf_format=module Forces the driver to use the CVF (Compressed Volume File) module cvf_module instead of auto-detection. If the kernel supports kmod, the cvf_format=xxx option also controls on-demand CVF module loading. This option is obsolete. cvf_option=option Option passed to the CVF module. This option is obsolete. debug Turn on the debug flag. A version string and a list of filesystem parameters will be printed (these data are also printed if the parameters appear to be inconsistent). discard If set, causes discard/TRIM commands to be issued to the block device when blocks are freed. This is useful for SSD devices and sparse/thinly-provisioned LUNs. dos1xfloppy If set, use a fallback default BIOS Parameter Block configuration, determined by backing device size. These static parameters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images. errors={panic|continue|remount-ro} Specify FAT behavior on critical errors: panic, continue without doing anything, or remount the partition in read-only mode (default behavior). fat={12|16|32} Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT type detection routine. Use with caution! iocharset=value Character set to use for converting between 8 bit characters and 16 bit Unicode characters. The default is iso8859-1. Long filenames are stored on disk in Unicode format. nfs={stale_rw|nostale_ro} Enable this only if you want to export the FAT filesystem over NFS. stale_rw: This option maintains an index (cache) of directory inodes which is used by the nfs-related code to improve look-ups. Full file operations (read/write) over NFS are supported but with cache eviction at NFS server, this could result in spurious ESTALE errors. nostale_ro: This option bases the inode number and file handle on the on-disk location of a file in the FAT directory entry. This ensures that ESTALE will not be returned after a file is evicted from the inode cache. However, it means that operations such as rename, create and unlink could cause file handles that previously pointed at one file to point at a different file, potentially causing data corruption. For this reason, this option also mounts the filesystem readonly. To maintain backward compatibility, -o nfs is also accepted, defaulting to stale_rw. tz=UTC This option disables the conversion of timestamps between local time (as used by Windows on FAT) and UTC (which Linux uses internally). This is particularly useful when mounting devices (like digital cameras) that are set to UTC in order to avoid the pitfalls of local time. time_offset=minutes Set offset for conversion of timestamps from local time used by FAT to UTC. I.e., minutes will be subtracted from each timestamp to convert it to UTC used internally by Linux. This is useful when the time zone set in the kernel via settimeofday(2) is not the time zone used by the filesystem. Note that this option still does not provide correct time stamps in all cases in presence of DST - time stamps in a different DST setting will be off by one hour. quiet Turn on the quiet flag. Attempts to chown or chmod files do not return errors, although they fail. Use with caution! rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO of the directory will just be ignored, and is used only by applications as a flag (e.g. its set for the customized folder). If you want to use ATTR_RO as read-only flag even for the directory, set this option. showexec If set, the execute permission bits of the file will be allowed only if the extension part of the name is .EXE, .COM, or .BAT. Not set by default. sys_immutable If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux. Not set by default. flush If set, the filesystem will try to flush to disk more early than normal. Not set by default. usefree Use the "free clusters" value stored on FSINFO. Itll be used to determine number of free clusters without scanning disk. But its not used by default, because recent Windows dont update it correctly in some case. If you are sure the "free clusters" on FSINFO is correct, by this option you can avoid scanning disk. dots, nodots, dotsOK=[yes|no] Various misguided attempts to force Unix or DOS conventions onto a FAT filesystem. Mount options for hfs creator=cccc, type=cccc Set the creator/type values as shown by the MacOS finder used for creating new files. Default values: '????'. uid=n, gid=n Set the owner and group of all files. (Default: the UID and GID of the current process.) dir_umask=n, file_umask=n, umask=n Set the umask used for all directories, all regular files, or all files and directories. Defaults to the umask of the current process. session=n Select the CDROM session to mount. Defaults to leaving that decision to the CDROM driver. This option will fail with anything but a CDROM as underlying device. part=n Select partition number n from the device. Only makes sense for CDROMs. Defaults to not parsing the partition table at all. quiet Dont complain about invalid mount options. Mount options for hpfs uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. case={lower|asis} Convert all files names to lower case, or leave them. (Default: case=lower.) conv=mode This option is obsolete and may fail or being ignored. nocheck Do not abort mounting when certain consistency checks fail. Mount options for iso9660 ISO 9660 is a standard describing a filesystem structure to be used on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the udf filesystem.) Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like restrictions on filename length), and in addition all characters are in upper case. Also there is no field for file ownership, protection, number of links, provision for block/character devices, etc. Rock Ridge is an extension to iso9660 that provides all of these UNIX-like features. Basically there are extensions to each directory record that supply all of the additional information, and when Rock Ridge is in use, the filesystem is indistinguishable from a normal UNIX filesystem (except that it is read-only, of course). norock Disable the use of Rock Ridge extensions, even if available. Cf. map. nojoliet Disable the use of Microsoft Joliet extensions, even if available. Cf. map. check={r[elaxed]|s[trict]} With check=relaxed, a filename is first converted to lower case before doing the lookup. This is probably only meaningful together with norock and map=normal. (Default: check=strict.) uid=value and gid=value Give all files in the filesystem the indicated user or group id, possibly overriding the information found in the Rock Ridge extensions. (Default: uid=0,gid=0.) map={n[ormal]|o[ff]|a[corn]} For non-Rock Ridge volumes, normal name translation maps upper to lower case ASCII, drops a trailing ';1', and converts ';' to '.'. With map=off no name translation is done. See norock. (Default: map=normal.) map=acorn is like map=normal but also apply Acorn extensions if present. mode=value For non-Rock Ridge volumes, give all files the indicated mode. (Default: read and execute permission for everybody.) Octal mode values require a leading 0. unhide Also show hidden and associated files. (If the ordinary files and the associated or hidden files have the same filenames, this may make the ordinary files inaccessible.) block={512|1024|2048} Set the block size to the indicated value. (Default: block=1024.) conv=mode This option is obsolete and may fail or being ignored. cruft If the high byte of the file length contains other garbage, set this mount option to ignore the high order bits of the file length. This implies that a file cannot be larger than 16 MB. session=x Select number of session on a multisession CD. sbsector=xxx Session begins from sector xxx. The following options are the same as for vfat and specifying them only makes sense when using discs encoded using Microsofts Joliet extensions. iocharset=value Character set to use for converting 16 bit Unicode characters on CD to 8 bit characters. The default is iso8859-1. utf8 Convert 16 bit Unicode characters on CD to UTF-8. Mount options for jfs iocharset=name Character set to use for converting from Unicode to ASCII. The default is to do no conversion. Use iocharset=utf8 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in the kernel .config file. resize=value Resize the volume to value blocks. JFS only supports growing a volume, not shrinking it. This option is only valid during a remount, when the volume is mounted read-write. The resize keyword with no value will grow the volume to the full size of the partition. nointegrity Do not write to the journal. The primary use of this option is to allow for higher performance when restoring a volume from backup media. The integrity of the volume is not guaranteed if the system abnormally ends. integrity Default. Commit metadata changes to the journal. Use this option to remount a volume where the nointegrity option was previously specified in order to restore normal behavior. errors={continue|remount-ro|panic} Define the behavior when an error is encountered. (Either ignore errors and just mark the filesystem erroneous and continue, or remount the filesystem read-only, or panic and halt the system.) noquota|quota|usrquota|grpquota These options are accepted but ignored. Mount options for msdos See mount options for fat. If the msdos filesystem detects an inconsistency, it reports an error and sets the file system read-only. The filesystem can be made writable again by remounting it. Mount options for ncpfs Just like nfs, the ncpfs implementation expects a binary argument (a struct ncp_mount_data) to the mount(2) system call. This argument is constructed by ncpmount(8) and the current version of mount (2.12) does not know anything about ncpfs. Mount options for ntfs iocharset=name Character set to use when returning file names. Unlike VFAT, NTFS suppresses names that contain nonconvertible characters. Deprecated. nls=name New name for the option earlier called iocharset. utf8 Use UTF-8 for converting file names. uni_xlate={0|1|2} For 0 (or 'no' or 'false'), do not use escape sequences for unknown Unicode characters. For 1 (or 'yes' or 'true') or 2, use vfat-style 4-byte escape sequences starting with ":". Here 2 gives a little-endian encoding and 1 a byteswapped bigendian encoding. posix=[0|1] If enabled (posix=1), the filesystem distinguishes between upper and lower case. The 8.3 alias names are presented as hard links instead of being suppressed. This option is obsolete. uid=value, gid=value and umask=value Set the file permission on the filesystem. The umask value is given in octal. By default, the files are owned by root and not readable by somebody else. Mount options for overlay Since Linux 3.18 the overlay pseudo filesystem implements a union mount for other filesystems. An overlay filesystem combines two filesystems - an upper filesystem and a lower filesystem. When a name exists in both filesystems, the object in the upper filesystem is visible while the object in the lower filesystem is either hidden or, in the case of directories, merged with the upper object. The lower filesystem can be any filesystem supported by Linux and does not need to be writable. The lower filesystem can even be another overlayfs. The upper filesystem will normally be writable and if it is it must support the creation of trusted.* extended attributes, and must provide a valid d_type in readdir responses, so NFS is not suitable. A read-only overlay of two read-only filesystems may use any filesystem type. The options lowerdir and upperdir are combined into a merged directory by using: mount -t overlay overlay \ -olowerdir=/lower,upperdir=/upper,workdir=/work /merged lowerdir=directory Any filesystem, does not need to be on a writable filesystem. upperdir=directory The upperdir is normally on a writable filesystem. workdir=directory The workdir needs to be an empty directory on the same filesystem as upperdir. userxattr Use the "user.overlay." xattr namespace instead of "trusted.overlay.". This is useful for unprivileged mounting of overlayfs. redirect_dir={on|off|follow|nofollow} If the redirect_dir feature is enabled, then the directory will be copied up (but not the contents). Then the "{trusted|user}.overlay.redirect" extended attribute is set to the path of the original location from the root of the overlay. Finally the directory is moved to the new location. on Redirects are enabled. off Redirects are not created and only followed if "redirect_always_follow" feature is enabled in the kernel/module config. follow Redirects are not created, but followed. nofollow Redirects are not created and not followed (equivalent to "redirect_dir=off" if "redirect_always_follow" feature is not enabled). index={on|off} Inode index. If this feature is disabled and a file with multiple hard links is copied up, then this will "break" the link. Changes will not be propagated to other names referring to the same inode. uuid={on|off} Can be used to replace UUID of the underlying filesystem in file handles with null, and effectively disable UUID checks. This can be useful in case the underlying disk is copied and the UUID of this copy is changed. This is only applicable if all lower/upper/work directories are on the same filesystem, otherwise it will fallback to normal behaviour. nfs_export={on|off} When the underlying filesystems supports NFS export and the "nfs_export" feature is enabled, an overlay filesystem may be exported to NFS. With the "nfs_export" feature, on copy_up of any lower object, an index entry is created under the index directory. The index entry name is the hexadecimal representation of the copy up origin file handle. For a non-directory object, the index entry is a hard link to the upper inode. For a directory object, the index entry has an extended attribute "{trusted|user}.overlay.upper" with an encoded file handle of the upper directory inode. When encoding a file handle from an overlay filesystem object, the following rules apply For a non-upper object, encode a lower file handle from lower inode For an indexed object, encode a lower file handle from copy_up origin For a pure-upper object and for an existing non-indexed upper object, encode an upper file handle from upper inode The encoded overlay file handle includes Header including path type information (e.g. lower/upper) UUID of the underlying filesystem Underlying filesystem encoding of underlying inode This encoding format is identical to the encoding format of file handles that are stored in extended attribute "{trusted|user}.overlay.origin". When decoding an overlay file handle, the following steps are followed Find underlying layer by UUID and path type information. Decode the underlying filesystem file handle to underlying dentry. For a lower file handle, lookup the handle in index directory by name. If a whiteout is found in index, return ESTALE. This represents an overlay object that was deleted after its file handle was encoded. For a non-directory, instantiate a disconnected overlay dentry from the decoded underlying dentry, the path type and index inode, if found. For a directory, use the connected underlying decoded dentry, path type and index, to lookup a connected overlay dentry. Decoding a non-directory file handle may return a disconnected dentry. copy_up of that disconnected dentry will create an upper index entry with no upper alias. When overlay filesystem has multiple lower layers, a middle layer directory may have a "redirect" to lower directory. Because middle layer "redirects" are not indexed, a lower file handle that was encoded from the "redirect" origin directory, cannot be used to find the middle or upper layer directory. Similarly, a lower file handle that was encoded from a descendant of the "redirect" origin directory, cannot be used to reconstruct a connected overlay path. To mitigate the cases of directories that cannot be decoded from a lower file handle, these directories are copied up on encode and encoded as an upper file handle. On an overlay filesystem with no upper layer this mitigation cannot be used NFS export in this setup requires turning off redirect follow (e.g. "redirect_dir=nofollow"). The overlay filesystem does not support non-directory connectable file handles, so exporting with the subtree_check exportfs configuration will cause failures to lookup files over NFS. When the NFS export feature is enabled, all directory index entries are verified on mount time to check that upper file handles are not stale. This verification may cause significant overhead in some cases. Note: the mount options index=off,nfs_export=on are conflicting for a read-write mount and will result in an error. xino={on|off|auto} The "xino" feature composes a unique object identifier from the real object st_ino and an underlying fsid index. The "xino" feature uses the high inode number bits for fsid, because the underlying filesystems rarely use the high inode number bits. In case the underlying inode number does overflow into the high xino bits, overlay filesystem will fall back to the non xino behavior for that inode. For a detailed description of the effect of this option please refer to https://docs.kernel.org/filesystems/overlayfs.html metacopy={on|off} When metadata only copy up feature is enabled, overlayfs will only copy up metadata (as opposed to whole file), when a metadata specific operation like chown/chmod is performed. Full file will be copied up later when file is opened for WRITE operation. In other words, this is delayed data copy up operation and data is copied up when there is a need to actually modify data. volatile Volatile mounts are not guaranteed to survive a crash. It is strongly recommended that volatile mounts are only used if data written to the overlay can be recreated without significant effort. The advantage of mounting with the "volatile" option is that all forms of sync calls to the upper filesystem are omitted. In order to avoid a giving a false sense of safety, the syncfs (and fsync) semantics of volatile mounts are slightly different than that of the rest of VFS. If any writeback error occurs on the upperdirs filesystem after a volatile mount takes place, all sync functions will return an error. Once this condition is reached, the filesystem will not recover, and every subsequent sync call will return an error, even if the upperdir has not experience a new error since the last sync call. When overlay is mounted with "volatile" option, the directory "$workdir/work/incompat/volatile" is created. During next mount, overlay checks for this directory and refuses to mount if present. This is a strong indicator that user should throw away upper and work directories and create fresh one. In very limited cases where the user knows that the system has not crashed and contents of upperdir are intact, The "volatile" directory can be removed. Mount options for reiserfs Reiserfs is a journaling filesystem. conv Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem, using the 3.6 format for newly created objects. This filesystem will no longer be compatible with reiserfs 3.5 tools. hash={rupasov|tea|r5|detect} Choose which hash function reiserfs will use to find files within directories. rupasov A hash invented by Yury Yu. Rupasov. It is fast and preserves locality, mapping lexicographically close file names to close hash values. This option should not be used, as it causes a high probability of hash collisions. tea A Davis-Meyer function implemented by Jeremy Fitzhardinge. It uses hash permuting bits in the name. It gets high randomness and, therefore, low probability of hash collisions at some CPU cost. This may be used if EHASHCOLLISION errors are experienced with the r5 hash. r5 A modified version of the rupasov hash. It is used by default and is the best choice unless the filesystem has huge directories and unusual file-name patterns. detect Instructs mount to detect which hash function is in use by examining the filesystem being mounted, and to write this information into the reiserfs superblock. This is only useful on the first mount of an old format filesystem. hashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. no_unhashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. noborder Disable the border allocator algorithm invented by Yury Yu. Rupasov. This may provide performance improvements in some situations. nolog Disable journaling. This will provide slight performance improvements in some situations at the cost of losing reiserfss fast recovery from crashes. Even with this option turned on, reiserfs still performs all journaling operations, save for actual writes into its journaling area. Implementation of nolog is a work in progress. notail By default, reiserfs stores small files and 'file tails' directly into its tree. This confuses some utilities such as lilo(8). This option is used to disable packing of files into the tree. replayonly Replay the transactions which are in the journal, but do not actually mount the filesystem. Mainly used by reiserfsck. resize=number A remount option which permits online expansion of reiserfs partitions. Instructs reiserfs to assume that the device has number blocks. This option is designed for use with devices which are under logical volume management (LVM). There is a special resizer utility which can be obtained from ftp://ftp.namesys.com/pub/reiserfsprogs. user_xattr Enable Extended User Attributes. See the attr(1) manual page. acl Enable POSIX Access Control Lists. See the acl(5) manual page. barrier=none / barrier=flush This disables / enables the use of write barriers in the journaling code. barrier=none disables, barrier=flush enables (default). This also requires an IO stack which can support barriers, and if reiserfs gets an error on a barrier write, it will disable barriers again with a warning. Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance penalty. If your disks are battery-backed in one way or another, disabling barriers may safely improve performance. Mount options for ubifs UBIFS is a flash filesystem which works on top of UBI volumes. Note that atime is not supported and is always turned off. The device name may be specified as ubiX_Y UBI device number X, volume number Y ubiY UBI device number 0, volume number Y ubiX:NAME UBI device number X, volume with name NAME ubi:NAME UBI device number 0, volume with name NAME Alternative ! separator may be used instead of :. The following mount options are available: bulk_read Enable bulk-read. VFS read-ahead is disabled because it slows down the filesystem. Bulk-Read is an internal optimization. Some flashes may read faster if the data are read at one go, rather than at several read requests. For example, OneNAND can do "read-while-load" if it reads more than one NAND page. no_bulk_read Do not bulk-read. This is the default. chk_data_crc Check data CRC-32 checksums. This is the default. no_chk_data_crc Do not check data CRC-32 checksums. With this option, the filesystem does not check CRC-32 checksum for data, but it does check it for the internal indexing information. This option only affects reading, not writing. CRC-32 is always calculated when writing the data. compr={none|lzo|zlib} Select the default compressor which is used when new files are written. It is still possible to read compressed files if mounted with the none option. Mount options for udf UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical Storage Technology Association, and is often used for DVD-ROM, frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, however, perfectly usable by itself on disk drives, flash drives and other block devices. See also iso9660. uid= Make all files in the filesystem belong to the given user. uid=forget can be specified independently of (or usually in addition to) uid=<user> and results in UDF not storing uids to the media. In fact the recorded uid is the 32-bit overflow uid -1 as defined by the UDF standard. The value is given as either <user> which is a valid user name or the corresponding decimal user id, or the special string "forget". gid= Make all files in the filesystem belong to the given group. gid=forget can be specified independently of (or usually in addition to) gid=<group> and results in UDF not storing gids to the media. In fact the recorded gid is the 32-bit overflow gid -1 as defined by the UDF standard. The value is given as either <group> which is a valid group name or the corresponding decimal group id, or the special string "forget". umask= Mask out the given permissions from all inodes read from the filesystem. The value is given in octal. mode= If mode= is set the permissions of all non-directory inodes read from the filesystem will be set to the given mode. The value is given in octal. dmode= If dmode= is set the permissions of all directory inodes read from the filesystem will be set to the given dmode. The value is given in octal. bs= Set the block size. Default value prior to kernel version 2.6.30 was 2048. Since 2.6.30 and prior to 4.11 it was logical device block size with fallback to 2048. Since 4.11 it is logical block size with fallback to any valid block size between logical device block size and 4096. For other details see the mkudffs(8) 2.0+ manpage, see the COMPATIBILITY and BLOCK SIZE sections. unhide Show otherwise hidden files. undelete Show deleted files in lists. adinicb Embed data in the inode. (default) noadinicb Dont embed data in the inode. shortad Use short UDF address descriptors. longad Use long UDF address descriptors. (default) nostrict Unset strict conformance. iocharset= Set the NLS character set. This requires kernel compiled with CONFIG_UDF_NLS option. utf8 Set the UTF-8 character set. Mount options for debugging and disaster recovery novrs Ignore the Volume Recognition Sequence and attempt to mount anyway. session= Select the session number for multi-session recorded optical media. (default= last session) anchor= Override standard anchor location. (default= 256) lastblock= Set the last block of the filesystem. Unused historical mount options that may be encountered and should be removed uid=ignore Ignored, use uid=<user> instead. gid=ignore Ignored, use gid=<group> instead. volume= Unimplemented and ignored. partition= Unimplemented and ignored. fileset= Unimplemented and ignored. rootdir= Unimplemented and ignored. Mount options for ufs ufstype=value UFS is a filesystem widely used in different operating systems. The problem are differences among implementations. Features of some implementations are undocumented, so its hard to recognize the type of ufs automatically. Thats why the user must specify the type of ufs by mount option. Possible values are: old Old format of ufs, this is the default, read only. (Dont forget to give the -r option.) 44bsd For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD). ufs2 Used in FreeBSD 5.x supported as read-write. 5xbsd Synonym for ufs2. sun For filesystems created by SunOS or Solaris on Sparc. sunx86 For filesystems created by Solaris on x86. hp For filesystems created by HP-UX, read-only. nextstep For filesystems created by NeXTStep (on NeXT station) (currently read only). nextstep-cd For NextStep CDROMs (block_size == 2048), read-only. openstep For filesystems created by OpenStep (currently read only). The same filesystem type is also used by macOS. onerror=value Set behavior on error: panic If an error is encountered, cause a kernel panic. [lock|umount|repair] These mount options dont do anything at present; when an error is encountered only a console message is printed. Mount options for umsdos See mount options for msdos. The dotsOK option is explicitly killed by umsdos. Mount options for vfat First of all, the mount options for fat are recognized. The dotsOK option is explicitly killed by vfat. Furthermore, there are uni_xlate Translate unhandled Unicode characters to special escaped sequences. This lets you backup and restore filenames that are created with any Unicode characters. Without this option, a '?' is used when no translation is possible. The escape character is ':' because it is otherwise invalid on the vfat filesystem. The escape sequence that gets used, where u is the Unicode character, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12). posix Allow two files with names that only differ in case. This option is obsolete. nonumtail First try to make a short name without sequence number, before trying name~num.ext. utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the console. It can be enabled for the filesystem with this option or disabled with utf8=0, utf8=no or utf8=false. If uni_xlate gets set, UTF8 gets disabled. shortname=mode Defines the behavior for creation and display of filenames which fit into 8.3 characters. If a long name for a file exists, it will always be the preferred one for display. There are four modes: lower Force the short name to lower case upon display; store a long name when the short name is not all upper case. win95 Force the short name to upper case upon display; store a long name when the short name is not all upper case. winnt Display the short name as is; store a long name when the short name is not all lower case or all upper case. mixed Display the short name as is; store a long name when the short name is not all upper case. This mode is the default since Linux 2.6.32. Mount options for usbfs devuid=uid and devgid=gid and devmode=mode Set the owner and group and mode of the device files in the usbfs filesystem (default: uid=gid=0, mode=0644). The mode is given in octal. busuid=uid and busgid=gid and busmode=mode Set the owner and group and mode of the bus directories in the usbfs filesystem (default: uid=gid=0, mode=0555). The mode is given in octal. listuid=uid and listgid=gid and listmode=mode Set the owner and group and mode of the file devices (default: uid=gid=0, mode=0444). The mode is given in octal. DM-VERITY SUPPORT top The device-mapper verity target provides read-only transparent integrity checking of block devices using kernel crypto API. The mount command can open the dm-verity device and do the integrity verification before the device filesystem is mounted. Requires libcryptsetup with in libmount (optionally via dlopen(3)). If libcryptsetup supports extracting the root hash of an already mounted device, existing devices will be automatically reused in case of a match. Mount options for dm-verity: verity.hashdevice=path Path to the hash tree device associated with the source volume to pass to dm-verity. verity.roothash=hex Hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothashfile. verity.roothashfile=path Path to file containing the hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothash. verity.hashoffset=offset If the hash tree device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the tree. verity.fecdevice=path Path to the Forward Error Correction (FEC) device associated with the source volume to pass to dm-verity. Optional. Requires kernel built with CONFIG_DM_VERITY_FEC. verity.fecoffset=offset If the FEC device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the FEC area. Optional. verity.fecroots=value Parity bytes for FEC (default: 2). Optional. verity.roothashsig=path Path to pkcs7(1ssl) signature of root hash hex string. Requires crypt_activate_by_signed_key() from cryptsetup and kernel built with CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG. For device reuse, signatures have to be either used by all mounts of a device or by none. Optional. verity.oncorruption=ignore|restart|panic Instruct the kernel to ignore, reboot or panic when corruption is detected. By default the I/O operation simply fails. Requires Linux 4.1 or newer, and libcrypsetup 2.3.4 or newer. Optional. Supported since util-linux v2.35. For example commands: mksquashfs /etc /tmp/etc.raw veritysetup format /tmp/etc.raw /tmp/etc.verity --root-hash-file=/tmp/etc.roothash openssl smime -sign -in /tmp/etc.roothash -nocerts -inkey private.key \ -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s mount -o verity.hashdevice=/tmp/etc.verity,verity.roothashfile=/tmp/etc.roothash,\ verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.raw /mnt create squashfs image from /etc directory, verity hash device and mount verified filesystem image to /mnt. The kernel will verify that the root hash is signed by a key from the kernel keyring if roothashsig is used. LOOP-DEVICE SUPPORT top One further possible type is a mount via the loop device. For example, the command mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3 will set up the loop device /dev/loop3 to correspond to the file /tmp/disk.img, and then mount this device on /mnt. If no explicit loop device is mentioned (but just an option '-o loop' is given), then mount will try to find some unused loop device and use that, for example mount /tmp/disk.img /mnt -o loop The mount command automatically creates a loop device from a regular file if a filesystem type is not specified or the filesystem is known for libblkid, for example: mount /tmp/disk.img /mnt mount -t ext4 /tmp/disk.img /mnt This type of mount knows about three options, namely loop, offset and sizelimit, that are really options to losetup(8). (These options can be used in addition to those specific to the filesystem type.) Since Linux 2.6.25 auto-destruction of loop devices is supported, meaning that any loop device allocated by mount will be freed by umount independently of /etc/mtab. You can also free a loop device by hand, using losetup -d or umount -d. Since util-linux v2.29, mount re-uses the loop device rather than initializing a new device if the same backing file is already used for some loop device with the same offset and sizelimit. This is necessary to avoid a filesystem corruption. EXIT STATUS top mount has the following exit status values (the bits can be ORed): 0 success 1 incorrect invocation or permissions 2 system error (out of memory, cannot fork, no more loop devices) 4 internal mount bug 8 user interrupt 16 problems writing or locking /etc/mtab 32 mount failure 64 some mount succeeded The command mount -a returns 0 (all succeeded), 32 (all failed), or 64 (some failed, some succeeded). EXTERNAL HELPERS top The syntax of external mount helpers is: /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t type.subtype] where the suffix is the filesystem type and the -sfnvoN options have the same meaning as the normal mount options. The -t option is used for filesystems with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs). The command mount does not pass the mount options unbindable, runbindable, private, rprivate, slave, rslave, shared, rshared, auto, noauto, comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers. All other options are used in a comma-separated list as an argument to the -o option. ENVIRONMENT top LIBMOUNT_FORCE_MOUNT2={always|never|auto} force to use classic mount(2) system call (requires support for new file descriptors based mount API). The default is auto; in this case, libmount tries to be smart and use classic mount(2) only for well-known issues. If the new mount API is unavailable, libmount can still use traditional mount(2), although LIBMOUNT_FORCE_MOUNT2 is set to never. LIBMOUNT_FSTAB=<path> overrides the default location of the fstab file (ignored for suid) LIBMOUNT_DEBUG=all enables libmount debug output LIBBLKID_DEBUG=all enables libblkid debug output LOOPDEV_DEBUG=all enables loop device setup debug output FILES top See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section above. /etc/fstab filesystem table /run/mount libmount private runtime directory /etc/mtab table of mounted filesystems or symlink to /proc/mounts /etc/mtab~ lock file (unused on systems with mtab symlink) /etc/mtab.tmp temporary file (unused on systems with mtab symlink) /etc/filesystems a list of filesystem types to try HISTORY top A mount command existed in Version 5 AT&T UNIX. BUGS top It is possible for a corrupted filesystem to cause a crash. Some Linux filesystems dont support -o sync and -o dirsync (the ext2, ext3, ext4, fat and vfat filesystems do support synchronous updates (a la BSD) when mounted with the sync option). The -o remount may not be able to change mount parameters (all ext2fs-specific parameters, except sb, are changeable with a remount, for example, but you cant change gid or umask for the fatfs). It is possible that the files /etc/mtab and /proc/mounts dont match on systems with a regular mtab file. The first file is based only on the mount command options, but the content of the second file also depends on the kernel and others settings (e.g. on a remote NFS server in certain cases the mount command may report unreliable information about an NFS mount point and the /proc/mount file usually contains more reliable information.) This is another reason to replace the mtab file with a symlink to the /proc/mounts file. Checking files on NFS filesystems referenced by file descriptors (i.e. the fcntl and ioctl families of functions) may lead to inconsistent results due to the lack of a consistency check in the kernel even if the noac mount option is used. The loop option with the offset or sizelimit options used may fail when using older kernels if the mount command cant confirm that the size of the block device has been configured as requested. This situation can be worked around by using the losetup(8) command manually before calling mount with the configured loop device. AUTHORS top Karel Zak <kzak@redhat.com> SEE ALSO top mount(2), umount(2), filesystems(5), fstab(5), nfs(5), xfs(5), mount_namespaces(7), xattr(7), e2label(8), findmnt(8), losetup(8), lsblk(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8), umount(8), xfs_admin(8) REPORTING BUGS top For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY top The mount command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at https://www.kernel.org/pub/linux/utils/util-linux/. If you have a bug report for this manual page, send it to util-linux@vger.kernel.org. This page was obtained from the project's upstream Git repository git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org util-linux 2.39.594-1e0ad 2023-08-25 MOUNT(8) Pages that refer to this page: eject(1), fusermount3(1), homectl(1), mountpoint(1), quotasync(1), systemd-dissect(1), systemd-mount(1), unshare(1), chown(2), fcntl(2), fsync(2), ioctl_iflags(2), mount(2), open(2), open_by_handle_at(2), umount(2), getmntent(3), getsubopt(3), fd(4), hd(4), loop(4), ram(4), autofs(5), ext4(5), filesystems(5), fstab(5), lxc.container.conf(5), nfs(5), nfsmount.conf(5), proc(5), repart.d(5), systemd.automount(5), systemd.exec(5), systemd.mount(5), tmpfs(5), xfs(5), bootparam(7), fanotify(7), file-hierarchy(7), hier(7), inode(7), man-pages(7), mount_namespaces(7), spufs(7), automount(8), blkid(8), btrfs-subvolume(8), e4crypt(8), e4defrag(8), findmnt(8), fsck.cramfs(8), fsck.xfs(8), fsfreeze(8), fstrim(8), lsof(8), mkfs.cramfs(8), mount(8), mount.fuse3(8), mount.nfs(8), pam_namespace(8), pivot_root(8), quotaon(8), swapon(8), switch_root(8), systemd-remount-fs.service(8), tune2fs(8), umount(8), wipefs(8), xfs_admin(8), xfs_db(8), xfs_freeze(8), xfs_growfs(8), xfs_info(8), xfs_logprint(8), xfs_rtcp(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if a drive is mounted to nfs Bash Command:<START>mount |grep nfs<END>

Check if a drive with UUID "$UUID" is mounted

mount | grep $(readlink -f /dev/disk/by-uuid/$UUID )

['mount', 'grep', 'readlink']

Output a Bash command to accomplish the following task. Task: Check if a drive with UUID "$UUID" is mounted Bash Command:<START>mount | grep $(readlink -f /dev/disk/by-uuid/$UUID )<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # mount\n\n> Provides access to an entire filesystem in one directory.\n> More information: <https://manned.org/mount.8>.\n\n- Show all mounted filesystems:\n\n`mount`\n\n- Mount a device to a directory:\n\n`mount -t {{filesystem_type}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Create a specific directory if it does not exist and mount a device to it:\n\n`mount --mkdir {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a device to a directory for a specific user:\n\n`mount -o uid={{user_id}},gid={{group_id}} {{path/to/device_file}} {{path/to/target_directory}}`\n\n- Mount a CD-ROM device (with the filetype ISO9660) to `/cdrom` (readonly):\n\n`mount -t {{iso9660}} -o ro {{/dev/cdrom}} {{/cdrom}}`\n\n- Mount all the filesystem defined in `/etc/fstab`:\n\n`mount -a`\n\n- Mount a specific filesystem described in `/etc/fstab` (e.g. `/dev/sda1 /my_drive ext2 defaults 0 2`):\n\n`mount {{/my_drive}}`\n\n- Mount a directory to another directory:\n\n`mount --bind {{path/to/old_dir}} {{path/to/new_dir}}`\n # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # readlink\n\n> Follow symlinks and get symlink information.\n> More information: <https://www.gnu.org/software/coreutils/readlink>.\n\n- Get the actual file to which the symlink points:\n\n`readlink {{path/to/file}}`\n\n- Get the absolute path to a file:\n\n`readlink -f {{path/to/file}}`\n Task: Check if a drive with UUID "$UUID" is mounted Bash Command:<START>mount | grep $(readlink -f /dev/disk/by-uuid/$UUID )<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: mount(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training mount(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND-LINE OPTIONS | FILESYSTEM-INDEPENDENT MOUNT OPTIONS | FILESYSTEM-SPECIFIC MOUNT OPTIONS | DM-VERITY SUPPORT | LOOP-DEVICE SUPPORT | EXIT STATUS | EXTERNAL HELPERS | ENVIRONMENT | FILES | HISTORY | BUGS | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY MOUNT(8) System Administration MOUNT(8) NAME top mount - mount a filesystem SYNOPSIS top mount [-h|-V] mount [-l] [-t fstype] mount -a [-fFnrsvw] [-t fstype] [-O optlist] mount [-fnrsvw] [-o options] device|mountpoint mount [-fnrsvw] [-t fstype] [-o options] device mountpoint mount --bind|--rbind|--move olddir newdir mount --make-[shared|slave|private|unbindable|rshared|rslave|rprivate|runbindable] mountpoint DESCRIPTION top All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the filesystem found on some device to the big file tree. Conversely, the umount(8) command will detach it again. The filesystem is used to control how data is stored on the device or provided in a virtual way by network or other services. The standard form of the mount command is: mount -t type device dir This tells the kernel to attach the filesystem found on device (which is of type type) at the directory dir. The option -t type is optional. The mount command is usually able to detect a filesystem. The root permissions are necessary to mount a filesystem by default. See section "Non-superuser mounts" below for more details. The previous contents (if any) and owner and mode of dir become invisible, and as long as this filesystem remains mounted, the pathname dir refers to the root of the filesystem on device. If only the directory or the device is given, for example: mount /dir then mount looks for a mountpoint (and if not found then for a device) in the /etc/fstab file. Its possible to use the --target or --source options to avoid ambiguous interpretation of the given argument. For example: mount --target /mountpoint The same filesystem may be mounted more than once, and in some cases (e.g., network filesystems) the same filesystem may be mounted on the same mountpoint multiple times. The mount command does not implement any policy to control this behavior. All behavior is controlled by the kernel and it is usually specific to the filesystem driver. The exception is --all, in this case already mounted filesystems are ignored (see --all below for more details). Listing the mounts The listing mode is maintained for backward compatibility only. For more robust and customizable output use findmnt(8), especially in your scripts. Note that control characters in the mountpoint name are replaced with '?'. The following command lists all mounted filesystems (of type type): mount [-l] [-t type] The option -l adds labels to this listing. See below. Indicating the device and filesystem Most devices are indicated by a filename (of a block special device), like /dev/sda1, but there are other possibilities. For example, in the case of an NFS mount, device may look like knuth.cwi.nl:/dir. The device names of disk partitions are unstable; hardware reconfiguration, and adding or removing a device can cause changes in names. This is the reason why its strongly recommended to use filesystem or partition identifiers like UUID or LABEL. Currently supported identifiers (tags): LABEL=label Human readable filesystem identifier. See also -L. UUID=uuid Filesystem universally unique identifier. The format of the UUID is usually a series of hex digits separated by hyphens. See also -U. Note that mount uses UUIDs as strings. The UUIDs from the command line or from fstab(5) are not converted to internal binary representation. The string representation of the UUID should be based on lower case characters. PARTLABEL=label Human readable partition identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). PARTUUID=uuid Partition universally unique identifier. This identifier is independent on filesystem and does not change by mkfs or mkswap operations. Its supported for example for GUID Partition Tables (GPT). ID=id Hardware block device ID as generated by udevd. This identifier is usually based on WWN (unique storage identifier) and assigned by the hardware manufacturer. See ls /dev/disk/by-id for more details, this directory and running udevd is required. This identifier is not recommended for generic use as the identifier is not strictly defined and it depends on udev, udev rules and hardware. The command lsblk --fs provides an overview of filesystems, LABELs and UUIDs on available block devices. The command blkid -p <device> provides details about a filesystem on the specified device. Dont forget that there is no guarantee that UUIDs and labels are really unique, especially if you move, share or copy the device. Use lsblk -o +UUID,PARTUUID to verify that the UUIDs are really unique in your system. The recommended setup is to use tags (e.g. UUID=uuid) rather than /dev/disk/by-{label,uuid,id,partuuid,partlabel} udev symlinks in the /etc/fstab file. Tags are more readable, robust and portable. The mount(8) command internally uses udev symlinks, so the use of symlinks in /etc/fstab has no advantage over tags. For more details see libblkid(3). The proc filesystem is not associated with a special device, and when mounting it, an arbitrary keyword - for example, proc - can be used instead of a device specification. (The customary choice none is less fortunate: the error message 'none already mounted' from mount can be confusing.) The files /etc/fstab, /etc/mtab and /proc/mounts The file /etc/fstab (see fstab(5)), may contain lines describing what devices are usually mounted where, using which options. The default location of the fstab(5) file can be overridden with the --fstab path command-line option (see below for more details). The command mount -a [-t type] [-O optlist] (usually given in a bootscript) causes all filesystems mentioned in fstab (of the proper type and/or having or not having the proper options) to be mounted as indicated, except for those whose line contains the noauto keyword. Adding the -F option will make mount fork, so that the filesystems are mounted in parallel. When mounting a filesystem mentioned in fstab or mtab, it suffices to specify on the command line only the device, or only the mount point. The programs mount and umount(8) traditionally maintained a list of currently mounted filesystems in the file /etc/mtab. The support for regular classic /etc/mtab is completely disabled at compile time by default, because on current Linux systems it is better to make /etc/mtab a symlink to /proc/mounts instead. The regular mtab file maintained in userspace cannot reliably work with namespaces, containers and other advanced Linux features. If the regular mtab support is enabled, then its possible to use the file as well as the symlink. If no arguments are given to mount, the list of mounted filesystems is printed. If you want to override mount options from /etc/fstab, you have to use the -o option: mount device|dir -o options and then the mount options from the command line will be appended to the list of options from /etc/fstab. This default behaviour can be changed using the --options-mode command-line option. The usual behavior is that the last option wins if there are conflicting ones. The mount program does not read the /etc/fstab file if both device (or LABEL, UUID, ID, PARTUUID or PARTLABEL) and dir are specified. For example, to mount device foo at /dir: mount /dev/foo /dir This default behaviour can be changed by using the --options-source-force command-line option to always read configuration from fstab. For non-root users mount always reads the fstab configuration. Non-superuser mounts Normally, only the superuser can mount filesystems. However, when fstab contains the user option on a line, anybody can mount the corresponding filesystem. Thus, given a line /dev/cdrom /cd iso9660 ro,user,noauto,unhide any user can mount the iso9660 filesystem found on an inserted CDROM using the command: mount /cd Note that mount is very strict about non-root users and all paths specified on command line are verified before fstab is parsed or a helper program is executed. Its strongly recommended to use a valid mountpoint to specify filesystem, otherwise mount may fail. For example its a bad idea to use NFS or CIFS source on command line. Since util-linux 2.35, mount does not exit when user permissions are inadequate according to libmounts internal security rules. Instead, it drops suid permissions and continues as regular non-root user. This behavior supports use-cases where root permissions are not necessary (e.g., fuse filesystems, user namespaces, etc). For more details, see fstab(5). Only the user that mounted a filesystem can unmount it again. If any user should be able to unmount it, then use users instead of user in the fstab line. The owner option is similar to the user option, with the restriction that the user must be the owner of the special file. This may be useful e.g. for /dev/fd if a login script makes the console user owner of this device. The group option is similar, with the restriction that the user must be a member of the group of the special file. The user mount option is accepted if no username is specified. If used in the format user=someone, the option is silently ignored and visible only for external mount helpers (/sbin/mount.<type>) for compatibility with some network filesystems. Bind mount operation Remount part of the file hierarchy somewhere else. The call is: mount --bind olddir newdir or by using this fstab entry: /olddir /newdir none bind After this call the same contents are accessible in two places. It is important to understand that "bind" does not create any second-class or special node in the kernel VFS. The "bind" is just another operation to attach a filesystem. There is nowhere stored information that the filesystem has been attached by a "bind" operation. The olddir and newdir are independent and the olddir may be unmounted. One can also remount a single file (on a single file). Its also possible to use a bind mount to create a mountpoint from a regular directory, for example: mount --bind foo foo The bind mount call attaches only (part of) a single filesystem, not possible submounts. The entire file hierarchy including submounts can be attached a second place by using: mount --rbind olddir newdir Note that the filesystem mount options maintained by the kernel will remain the same as those on the original mount point. The userspace mount options (e.g., _netdev) will not be copied by mount and its necessary to explicitly specify the options on the mount command line. Since util-linux 2.27 mount permits changing the mount options by passing the relevant options along with --bind. For example: mount -o bind,ro foo foo This feature is not supported by the Linux kernel; it is implemented in userspace by an additional mount(2) remounting system call. This solution is not atomic. The alternative (classic) way to create a read-only bind mount is to use the remount operation, for example: mount --bind olddir newdir mount -o remount,bind,ro olddir newdir Note that a read-only bind will create a read-only mountpoint (VFS entry), but the original filesystem superblock will still be writable, meaning that the olddir will be writable, but the newdir will be read-only. Its also possible to change nosuid, nodev, noexec, noatime, nodiratime, relatime and nosymfollow VFS entry flags via a "remount,bind" operation. The other flags (for example filesystem-specific flags) are silently ignored. The classic mount(2) system call does not allow to change mount options recursively (for example with -o rbind,ro). The recursive semantic is possible with a new mount_setattr(2) kernel system call and its supported since libmount from util-linux v2.39 by a new experimental "recursive" option argument (e.g. -o rbind,ro=recursive). For more details see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS section. Since util-linux 2.31, mount ignores the bind flag from /etc/fstab on a remount operation (if -o remount is specified on command line). This is necessary to fully control mount options on remount by command line. In previous versions the bind flag has been always applied and it was impossible to re-define mount options without interaction with the bind semantic. This mount behavior does not affect situations when "remount,bind" is specified in the /etc/fstab file. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink. This feature is usable (only) with the new kernel mount API where bind mount over symlinks is supported. The move operation Move a mounted tree to another place (atomically). The call is: mount --move olddir newdir This will cause the contents which previously appeared under olddir to now be accessible under newdir. The physical location of the files is not changed. Note that olddir has to be a mountpoint. Note also that moving a mount residing under a shared mount is invalid and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current propagation flags. Shared subtree operations Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, private, slave or unbindable. A shared mount provides the ability to create mirrors of that mount such that mounts and unmounts within any of the mirrors propagate to the other mirror. A slave mount receives propagation from its master, but not vice versa. A private mount carries no propagation abilities. An unbindable mount is a private mount which cannot be cloned through a bind operation. The detailed semantics are documented in Documentation/filesystems/sharedsubtree.txt file in the kernel source tree; see also mount_namespaces(7). Supported operations are: mount --make-shared mountpoint mount --make-slave mountpoint mount --make-private mountpoint mount --make-unbindable mountpoint The following commands allow one to recursively change the type of all the mounts under a given mountpoint. mount --make-rshared mountpoint mount --make-rslave mountpoint mount --make-rprivate mountpoint mount --make-runbindable mountpoint mount does not read fstab(5) when a --make-* operation is requested. All necessary information has to be specified on the command line. Note that the Linux kernel does not allow changing multiple propagation flags with a single mount(2) system call, and the flags cannot be mixed with other mount options and operations. Since util-linux 2.23 the mount command can be used to do more propagation (topology) changes by one mount(8) call and do it also together with other mount operations. The propagation flags are applied by additional mount(2) system calls when the preceding mount operations were successful. Note that this use case is not atomic. It is possible to specify the propagation flags in fstab(5) as mount options (private, slave, shared, unbindable, rprivate, rslave, rshared, runbindable). For example: mount --make-private --make-unbindable /dev/sda1 /foo is the same as: mount /dev/sda1 /foo mount --make-private /foo mount --make-unbindable /foo COMMAND-LINE OPTIONS top The full set of mount options used by an invocation of mount is determined by first extracting the mount options for the filesystem from the fstab table, then applying any options specified by the -o argument, and finally applying a -r or -w option, when present. The mount command does not pass all command-line options to the /sbin/mount.suffix mount helpers. The interface between mount and the mount helpers is described below in the EXTERNAL HELPERS section. Command-line options available for the mount command are: -a, --all Mount all filesystems (of the given types) mentioned in fstab (except for those whose line contains the noauto keyword). The filesystems are mounted following their order in fstab. The mount command compares filesystem source, target (and fs root for bind mount or btrfs) to detect already mounted filesystems. The kernel table with already mounted filesystems is cached during mount --all. This means that all duplicated fstab entries will be mounted. The correct functionality depends on /proc (to detect already mounted filesystems) and on /sys (to evaluate filesystem tags like UUID= or LABEL=). Its strongly recommended to mount /proc and /sys filesystems before mount -a is executed, or keep /proc and /sys at the beginning of fstab. The option --all is possible to use for remount operation too. In this case all filters (-t and -O) are applied to the table of already mounted filesystems. Since version 2.35 it is possible to use the command line option -o to alter mount options from fstab (see also --options-mode). Note that it is a bad practice to use mount -a for fstab checking. The recommended solution is findmnt --verify. -B, --bind Remount a subtree somewhere else (so that its contents are available in both places). See above, under Bind mount operation. -c, --no-canonicalize Dont canonicalize paths. The mount command canonicalizes all paths (from the command line or fstab) by default. The option is designed for mount helpers which call mount -i. It is strongly recommended to not use this command-line option for normal mount operations. Since util-linux 2.40, mount does not canonicalize the mountpoint path on bind operation if the target is a symlink (see "Bind mount operation" section for more details). Note that mount does not pass this option to the /sbin/mount.type helpers. -F, --fork (Used in conjunction with -a.) Fork off a new incarnation of mount for each device. This will do the mounts on different devices or different NFS servers in parallel. This has the advantage that it is faster; also NFS timeouts proceed in parallel. A disadvantage is that the order of the mount operations is undefined. Thus, you cannot use this option if you want to mount both /usr and /usr/spool. -f, --fake Causes everything to be done except for the mount-related system calls. The --fake option was originally designed to write an entry to /etc/mtab without actually mounting. The /etc/mtab is no longer maintained in userspace, and starting from version 2.39, the mount operation can be a complex chain of operations with dependencies between the syscalls. The --fake option forces libmount to skip all mount source preparation, mount option analysis, and the actual mounting process. The difference between fake and non-fake execution is huge. This is the reason why the --fake option has minimal significance for the current mount(8) implementation and it is maintained mostly for backward compatibility. -i, --internal-only Dont call the /sbin/mount.filesystem helper even if it exists. -L, --label label Mount the partition that has the specified label. -l, --show-labels Add the labels in the mount output. mount must have permission to read the disk device (e.g. be set-user-ID root) for this to work. One can set such a label for ext2, ext3 or ext4 using the e2label(8) utility, or for XFS using xfs_admin(8), or for reiserfs using reiserfstune(8). -M, --move Move a subtree to some other place. See above, the subsection The move operation. -m, --mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. Alias to "-o X-mount.mkdir[=mode]", the default mode is 0755. For more details see X-mount.mkdir below. --map-groups, --map-users inner:_outer_:_count_ Add the specified user/group mapping to an X-mount.idmap map. These options can be given multiple times to build up complete mappings for users and groups. For more details see X-mount.idmap below. --map-users /proc/PID/ns/user Use the specified user namespace for user and group mapping in an id-mapped mount. This is an alias for "-o X-mount.idmap=/proc/PID/ns/user" and cannot be used twice nor together with the inner:_outer_:_count_ option format above. For more details see X-mount.idmap below. -n, --no-mtab Mount without writing in /etc/mtab. This is necessary for example when /etc is on a read-only filesystem. -N, --namespace ns Perform the mount operation in the mount namespace specified by ns. ns is either PID of process running in that namespace or special file representing that namespace. mount switches to the mount namespace when it reads /etc/fstab, writes /etc/mtab: (or writes to _/run/mount) and calls mount(2), otherwise it runs in the original mount namespace. This means that the target namespace does not have to contain any libraries or other requirements necessary to execute the mount(2) call. See mount_namespaces(7) for more information. -O, --test-opts opts Limit the set of filesystems to which the -a option applies. In this regard it is like the -t option except that -O is useless without -a. For example, the command mount -a -O no_netdev mounts all filesystems except those which have the option netdev specified in the options field in the /etc/fstab file. It is different from -t in that each option is matched exactly; a leading no at the beginning of one option does not negate the rest. The -t and -O options are cumulative in effect; that is, the command mount -a -t ext2 -O _netdev mounts all ext2 filesystems with the _netdev option, not all filesystems that are either ext2 or have the _netdev option specified. -o, --options opts Use the specified mount options. The opts argument is a comma-separated list. For example: mount LABEL=mydisk -o noatime,nodev,nosuid Note that the order of the options matters, as the last option wins if there are conflicting ones. The options from the command line also overwrite options from fstab by default. For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections. --onlyonce Forces mount command to check if the filesystem is already mounted. This behavior is the default for --all; otherwise, it depends on the kernel filesystem driver. Some filesystems may be mounted more than once on the same mount point (e.g. tmpfs). --options-mode mode Controls how to combine options from fstab/mtab with options from the command line. mode can be one of ignore, append, prepend or replace. For example, append means that options from fstab are appended to options from the command line. The default value is prepend it means command line options are evaluated after fstab options. Note that the last option wins if there are conflicting ones. --options-source source Source of default options. source is a comma-separated list of fstab, mtab and disable. disable disables fstab and mtab and enables --options-source-force. The default value is fstab,mtab. --options-source-force Use options from fstab/mtab even if both device and dir are specified. -R, --rbind Remount a subtree and all possible submounts somewhere else (so that its contents are available in both places). See above, the subsection Bind mount operation. -r, --read-only Mount the filesystem read-only. A synonym is -o ro. Note that, depending on the filesystem type, state and kernel behavior, the system may still write to the device. For example, ext3 and ext4 will replay the journal if the filesystem is dirty. To prevent this kind of write access, you may want to mount an ext3 or ext4 filesystem with the ro,noload mount options or set the block device itself to read-only mode, see the blockdev(8) command. -s Tolerate sloppy mount options rather than failing. This will ignore mount options not supported by a filesystem type. Not all filesystems support this option. Currently its supported by the mount.nfs mount helper only. --source device If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount source. --target directory If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount target. --target-prefix directory Prepend the specified directory to all mount targets. This option can be used to follow fstab, but mount operations are done in another place, for example: mount --all --target-prefix /chroot -o X-mount.mkdir mounts all from system fstab to /chroot, all missing mountpoint are created (due to X-mount.mkdir). See also --fstab to use an alternative fstab. -T, --fstab path Specifies an alternative fstab file. If path is a directory, then the files in the directory are sorted by strverscmp(3); files that start with "." or without an .fstab extension are ignored. The option can be specified more than once. This option is mostly designed for initramfs or chroot scripts where additional configuration is specified beyond standard system configuration. Note that mount does not pass the option --fstab to the /sbin/mount.type helpers, meaning that the alternative fstab files will be invisible for the helpers. This is no problem for normal mounts, but user (non-root) mounts always require fstab to verify the users rights. -t, --types fstype The argument following the -t is used to indicate the filesystem type. The filesystem types which are currently supported depend on the running kernel. See /proc/filesystems and /lib/modules/$(uname -r)/kernel/fs for a complete list of the filesystems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs. The programs mount and umount(8) support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For example 'fuse.sshfs'. Its recommended to use subtype notation rather than add any prefix to the mount source (for example 'sshfs#example.com' is deprecated). If no -t option is given, or if the auto type is specified, mount will try to guess the desired type. mount uses the libblkid(3) library for guessing the filesystem type; if that does not turn up anything that looks familiar, mount will try to read the file /etc/filesystems, or, if that does not exist, /proc/filesystems. All of the filesystem types listed there will be tried, except for those that are labeled "nodev" (e.g. devpts, proc and nfs). If /etc/filesystems ends in a line with a single *, mount will read /proc/filesystems afterwards. While trying, all filesystem types will be mounted with the mount option silent. The auto type may be useful for user-mounted floppies. Creating a file /etc/filesystems can be useful to change the probe order (e.g., to try vfat before msdos or ext3 before ext2) or if you use a kernel module autoloader. More than one type may be specified in a comma-separated list, for the -t option as well as in an /etc/fstab entry. The list of filesystem types for the -t option can be prefixed with no to specify the filesystem types on which no action should be taken. The prefix no has no effect when specified in an /etc/fstab entry. The prefix no can be meaningful with the -a option. For example, the command mount -a -t nomsdos,smbfs mounts all filesystems except those of type msdos and smbfs. For most types all the mount program has to do is issue a simple mount(2) system call, and no detailed knowledge of the filesystem type is required. For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems have a separate mount program. In order to make it possible to treat all types in a uniform way, mount will execute the program /sbin/mount.type (if that exists) when called with type type. Since different versions of the smbmount program have different calling conventions, /sbin/mount.smbfs may have to be a shell script that sets up the desired call. -U, --uuid uuid Mount the partition that has the specified uuid. -v, --verbose Verbose mode. -w, --rw, --read-write Mount the filesystem read/write. Read-write is the kernel default and the mount default is to try read-only if the previous mount(2) syscall with read-write flags on write-protected devices failed. A synonym is -o rw. Note that specifying -w on the command line forces mount to never try read-only mount on write-protected devices or already mounted read-only filesystems. -h, --help Display help text and exit. -V, --version Print version and exit. FILESYSTEM-INDEPENDENT MOUNT OPTIONS top Some of these options are only useful when they appear in the /etc/fstab file. Some of these options could be enabled or disabled by default in the system kernel. To check the current setting see the options in /proc/mounts. Note that filesystems also have per-filesystem specific default mount options (see for example tune2fs -l output for extN filesystems). The options nosuid, noexec, nodiratime, relatime, noatime, strictatime, and nosymfollow are interpreted only by the abstract VFS kernel layer and applied to the mountpoint node rather than to the filesystem itself. Try: findmnt -o TARGET,VFS-OPTIONS,FS-OPTIONS to get a complete overview of filesystems and VFS options. The read-only setting (ro or rw) is interpreted by VFS and the filesystem and depends on how the option is specified on the mount(8) command line. The default is to interpret it on the filesystem level. The operation "-o bind,remount,ro" is applied only to the VFS mountpoint, and operation "-o remount,ro" is applied to VFS and filesystem superblock. This semantic allows create a read-only mountpoint but keeps the filesystem writable from another mountpoint. Since v2.39 libmount can use a new kernel mount interface to set the VFS options recursive. For backward compatibility, this feature is not enabled by default, although recursive operation (e.g. rbind) has been requested. The new option argument "recursive" could be specified, for example: mount -orbind,ro=recursive,noexec=recursive,nosuid /foo /bar recursively binds filesystems from /foo to /bar, /bar, and all submounts will be read-only and noexec, but only /bar itself will be "nosuid". The "recursive" optional argument for VFS mount options is an EXPERIMENTAL feature. The following options apply to any filesystem that is being mounted (but not every filesystem actually honors them - e.g., the sync option today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs): async All I/O to the filesystem should be done asynchronously. (See also the sync option.) atime Do not use the noatime feature, so the inode access time is controlled by kernel defaults. See also the descriptions of the relatime and strictatime mount options. noatime Do not update inode access times on this filesystem (e.g. for faster access on the news spool to speed up news servers). This works for all inode types (directories too), so it implies nodiratime. auto Can be mounted with the -a option. noauto Can only be mounted explicitly (i.e., the -a option will not cause the filesystem to be mounted). context=context, fscontext=context, defcontext=context, and rootcontext=context The context= option is useful when mounting filesystems that do not support extended attributes, such as a floppy or hard disk formatted with VFAT, or systems that are not normally running under SELinux, such as an ext3 or ext4 formatted disk from a non-SELinux workstation. You can also use context= on filesystems you do not trust, such as a floppy. It also helps in compatibility with xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where xattrs are supported, you can save time not having to label every file by assigning the entire disk one security context. A commonly used option for removable media is context="system_u:object_r:removable_t. The fscontext= option works for all filesystems, regardless of their xattr support. The fscontext option sets the overarching filesystem label to a specific security context. This filesystem label is separate from the individual labels on the files. It represents the entire filesystem for certain kinds of permission checks, such as during mount or file creation. Individual file labels are still obtained from the xattrs on the files themselves. The context option actually sets the aggregate context that fscontext provides, in addition to supplying the same label for individual files. You can set the default security context for unlabeled files using defcontext= option. This overrides the value set for unlabeled files in the policy and requires a filesystem that supports xattr labeling. The rootcontext= option allows you to explicitly label the root inode of a FS being mounted before that FS or inode becomes visible to userspace. This was found to be useful for things like stateless Linux. The special value @target can be used to assign the current context of the target mountpoint location. Note that the kernel rejects any remount request that includes the context option, even when unchanged from the current context. Warning: the context value might contain commas, in which case the value has to be properly quoted, otherwise mount will interpret the comma as a separator between mount options. Dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t tmpfs none /mnt -o \ 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec' For more details, see selinux(8). defaults Use the default options: rw, suid, dev, exec, auto, nouser, and async. Note that the real set of all default mount options depends on the kernel and filesystem type. See the beginning of this section for more details. dev Interpret character or block special devices on the filesystem. nodev Do not interpret character or block special devices on the filesystem. diratime Update directory inode access times on this filesystem. This is the default. (This option is ignored when noatime is set.) nodiratime Do not update directory inode access times on this filesystem. (This option is implied when noatime is set.) dirsync All directory updates within the filesystem should be done synchronously. This affects the following system calls: creat(2), link(2), unlink(2), symlink(2), mkdir(2), rmdir(2), mknod(2) and rename(2). exec Permit execution of binaries and other executable files. noexec Do not permit direct execution of any binaries on the mounted filesystem. group Allow an ordinary user to mount the filesystem if one of that users groups matches the group of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line group,dev,suid). iversion Every time the inode is modified, the i_version field will be incremented. noiversion Do not increment the i_version inode field. mand Allow mandatory locks on this filesystem. See fcntl(2). This option was deprecated in Linux 5.15. nomand Do not allow mandatory locks on this filesystem. _netdev The filesystem resides on a device that requires network access (used to prevent the system from attempting to mount these filesystems until the network has been enabled on the system). nofail Do not report errors for this device if it does not exist. relatime Update inode access times relative to modify or change time. Access time is only updated if the previous access time was earlier than or equal to the current modify or change time. (Similar to noatime, but it doesnt break mutt(1) or other applications that need to know if a file has been read since the last time it was modified.) Since Linux 2.6.30, the kernel defaults to the behavior provided by this option (unless noatime was specified), and the strictatime option is required to obtain traditional semantics. In addition, since Linux 2.6.30, the files last access time is always updated if it is more than 1 day old. norelatime Do not use the relatime feature. See also the strictatime mount option. strictatime Allows to explicitly request full atime updates. This makes it possible for the kernel to default to relatime or noatime but still allow userspace to override it. For more details about the default system mount options see /proc/mounts. nostrictatime Use the kernels default behavior for inode access time updates. lazytime Only update times (atime, mtime, ctime) on the in-memory version of the file inode. This mount option significantly reduces writes to the inode table for workloads that perform frequent random writes to preallocated files. The on-disk timestamps are updated only when: the inode needs to be updated for some change unrelated to file timestamps the application employs fsync(2), syncfs(2), or sync(2) an undeleted inode is evicted from memory more than 24 hours have passed since the inode was written to disk. nolazytime Do not use the lazytime feature. suid Honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. nosuid Do not honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. In addition, SELinux domain transitions require permission nosuid_transition, which in turn needs also policy capability nnp_nosuid_transition. silent Turn on the silent flag. loud Turn off the silent flag. owner Allow an ordinary user to mount the filesystem if that user is the owner of the device. This option implies the options nosuid and nodev (unless overridden by subsequent options, as in the option line owner,dev,suid). remount Attempt to remount an already-mounted filesystem. This is commonly used to change the mount flags for a filesystem, especially to make a readonly filesystem writable. It does not change device or mount point. The remount operation together with the bind flag has special semantics. See above, the subsection Bind mount operation. The default kernel behavior for VFS mount flags (nodev,nosuid,noexec,ro) is to reset all unspecified flags on remount. Thats why mount(8) tries to keep the current setting according to fstab or /proc/self/mountinfo. This default behavior is possible to change by --options-mode. The recursive change of the mount flags (supported since v2.39 on systems with mount_setattr(2) syscall), for example, mount -o remount,ro=recursive, do not use "reset-unspecified" behavior, and it works as a simple add/remove operation and unspecified flags are not modified. The remount functionality follows the standard way the mount command works with options from fstab. This means that mount does not read fstab (or mtab) only when both device and dir are specified. mount -o remount,rw /dev/foo /dir After this call all old mount options are replaced and arbitrary stuff from fstab (or mtab) is ignored, except the loop= option which is internally generated and maintained by the mount command. mount -o remount,rw /dir After this call, mount reads fstab and merges these options with the options from the command line (-o). If no mountpoint is found in fstab, then it defaults to mount options from /proc/self/mountinfo. mount allows the use of --all to remount all already mounted filesystems which match a specified filter (-O and -t). For example: mount --all -o remount,ro -t vfat remounts all already mounted vfat filesystems in read-only mode. Each of the filesystems is remounted by mount -o remount,ro /dir semantic. This means the mount command reads fstab or mtab and merges these options with the options from the command line. ro Mount the filesystem read-only. rw Mount the filesystem read-write. sync All I/O to the filesystem should be done synchronously. In the case of media with a limited number of write cycles (e.g. some flash drives), sync may cause life-cycle shortening. user Allow an ordinary user to mount the filesystem. The name of the mounting user is written to the mtab file (or to the private libmount file in /run/mount on systems without a regular mtab) so that this same user can unmount the filesystem again. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line user,exec,dev,suid). nouser Forbid an ordinary user to mount the filesystem. This is the default; it does not imply any other options. users Allow any user to mount and to unmount the filesystem, even when some other ordinary user mounted it. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line users,exec,dev,suid). X-* All options prefixed with "X-" are interpreted as comments or as userspace application-specific options. These options are not stored in user space (e.g., mtab file), nor sent to the mount.type helpers nor to the mount(2) system call. The suggested format is X-appname.option. x-* The same as X-* options, but stored permanently in user space. This means the options are also available for umount(8) or other operations. Note that maintaining mount options in user space is tricky, because its necessary use libmount-based tools and there is no guarantee that the options will be always available (for example after a move mount operation or in unshared namespace). Note that before util-linux v2.30 the x-* options have not been maintained by libmount and stored in user space (functionality was the same as for X-* now), but due to the growing number of use-cases (in initrd, systemd etc.) the functionality has been extended to keep existing fstab configurations usable without a change. X-mount.auto-fstypes=list Specifies allowed or forbidden filesystem types for automatic filesystem detection. The list is a comma-separated list of the filesystem names. The automatic filesystem detection is triggered by the "auto" filesystem type or when the filesystem type is not specified. Thy list follows how mount evaluates type patterns (see -t for more details). Only specified filesystem types are allowed, or all specified types are forbidden if the list is prefixed by "no". For example, X-mount.auto-fstypes="ext4,btrfs" accepts only ext4 and btrfs, and X-mount.auto-fstypes="novfat,xfs" accepts all filesystems except vfat and xfs. Note that comma is used as a separator between mount options, it means that auto-fstypes values have to be properly quoted, dont forget that the shell strips off quotes and thus double quoting is required. For example: mount -t auto -oX-mount.auto-fstypes="noext2,ext3"' /dev/sdc1 /mnt/test X-mount.mkdir[=mode] Allow to make a target directory (mountpoint) if it does not exist yet. The optional argument mode specifies the filesystem access mode used for mkdir(2) in octal notation. The default mode is 0755. This functionality is supported only for root users or when mount is executed without suid permissions. The option is also supported as x-mount.mkdir, but this notation is deprecated since v2.30. See also --mkdir command line option. X-mount.subdir=directory Allow mounting sub-directory from a filesystem instead of the root directory. For now, this feature is implemented by temporary filesystem root directory mount in unshared namespace and then bind the sub-directory to the final mount point and umount the root of the filesystem. The sub-directory mount shows up atomically for the rest of the system although it is implemented by multiple mount(2) syscalls. Note that this feature will not work in session with an unshared private mount namespace (after unshare --mount) on old kernels or with mount(8) without support for file-descriptors-based mount kernel API. In this case, you need unshare --mount --propagation shared. This feature is EXPERIMENTAL. X-mount.owner=username|UID, X-mount.group=group|GID Set mountpoint's ownership after mounting. Names resolved in the target mount namespace, see -N. X-mount.mode=mode Set mountpoint's mode after mounting. X-mount.idmap=id-type:id-mount:id-host:id-range [id-type:id-mount:id-host:id-range], X-mount.idmap=file Use this option to create an idmapped mount. An idmapped mount allows to change ownership of all files located under a mount according to the ID-mapping associated with a user namespace. The ownership change is tied to the lifetime and localized to the relevant mount. The relevant ID-mapping can be specified in two ways: A user can specify the ID-mapping directly. The ID-mapping must be specified using the syntax id-type:id-mount:id-host:id-range. Specifying u as the id-type prefix creates a UID-mapping, g creates a GID-mapping and omitting id-type or specifying b creates both a UID- and GID-mapping. The id-mount parameter indicates the starting ID in the new mount. The id-host parameter indicates the starting ID in the filesystem. The id-range parameter indicates how many IDs are to be mapped. It is possible to specify multiple ID-mappings. The individual ID-mappings must be separated by spaces. For example, the ID-mapping X-mount.idmap=u:1000:0:1 g:1001:1:2 5000:1000:2 creates an idmapped mount where UID 0 is mapped to UID 1000, GID 1 is mapped to GUID 1001, GID 2 is mapped to GID 1002, UID and GID 1000 are mapped to 5000, and UID and GID 1001 are mapped to 5001 in the mount. When an ID-mapping is specified directly a new user namespace will be allocated with the requested ID-mapping. The newly created user namespace will be attached to the mount. A user can specify a user namespace file. The user namespace will then be attached to the mount and the ID-mapping of the user namespace will become the ID-mapping of the mount. For example, X-mount.idmap=/proc/PID/ns/user will attach the user namespace of the process PID to the mount. nosymfollow Do not follow symlinks when resolving paths. Symlinks can still be created, and readlink(1), readlink(2), realpath(1), and realpath(3) all still work properly. FILESYSTEM-SPECIFIC MOUNT OPTIONS top This section lists options that are specific to particular filesystems. Where possible, you should first consult filesystem-specific manual pages for details. Some of those pages are listed in the following table. Filesystem(s) Manual page btrfs btrfs(5) cifs mount.cifs(8) ext2, ext3, ext4 ext4(5) fuse fuse(8) nfs nfs(5) tmpfs tmpfs(5) xfs xfs(5) Note that some of the pages listed above might be available only after you install the respective userland tools. The following options apply only to certain filesystems. We sort them by filesystem. All options follow the -o flag. What options are supported depends a bit on the running kernel. Further information may be available in filesystem-specific files in the kernel source subdirectory Documentation/filesystems. Mount options for adfs uid=value and gid=value Set the owner and group of the files in the filesystem (default: uid=gid=0). ownmask=value and othmask=value Set the permission mask for ADFS 'owner' permissions and 'other' permissions, respectively (default: 0700 and 0077, respectively). See also /usr/src/linux/Documentation/filesystems/adfs.rst. Mount options for affs uid=value and gid=value Set the owner and group of the root of the filesystem (default: uid=gid=0, but with option uid or gid without specified value, the UID and GID of the current process are taken). setuid=value and setgid=value Set the owner and group of all files. mode=value Set the mode of all files to value & 0777 disregarding the original permissions. Add search permission to directories that have read permission. The value is given in octal. protect Do not allow any changes to the protection bits on the filesystem. usemp Set UID and GID of the root of the filesystem to the UID and GID of the mount point upon the first sync or umount, and then clear this option. Strange... verbose Print an informational message for each successful mount. prefix=string Prefix used before volume name, when following a link. volume=string Prefix (of length at most 30) used before '/' when following a symbolic link. reserved=value (Default: 2.) Number of unused blocks at the start of the device. root=value Give explicitly the location of the root block. bs=value Give blocksize. Allowed values are 512, 1024, 2048, 4096. grpquota|noquota|quota|usrquota These options are accepted but ignored. (However, quota utilities may react to such strings in /etc/fstab.) Mount options for debugfs The debugfs filesystem is a pseudo filesystem, traditionally mounted on /sys/kernel/debug. As of kernel version 3.4, debugfs has the following options: uid=n, gid=n Set the owner and group of the mountpoint. mode=value Sets the mode of the mountpoint. Mount options for devpts The devpts filesystem is a pseudo filesystem, traditionally mounted on /dev/pts. In order to acquire a pseudo terminal, a process opens /dev/ptmx; the number of the pseudo terminal is then made available to the process and the pseudo terminal slave can be accessed as /dev/pts/<number>. uid=value and gid=value This sets the owner or the group of newly created pseudo terminals to the specified values. When nothing is specified, they will be set to the UID and GID of the creating process. For example, if there is a tty group with GID 5, then gid=5 will cause newly created pseudo terminals to belong to the tty group. mode=value Set the mode of newly created pseudo terminals to the specified value. The default is 0600. A value of mode=620 and gid=5 makes "mesg y" the default on newly created pseudo terminals. newinstance Create a private instance of the devpts filesystem, such that indices of pseudo terminals allocated in this new instance are independent of indices created in other instances of devpts. All mounts of devpts without this newinstance option share the same set of pseudo terminal indices (i.e., legacy mode). Each mount of devpts with the newinstance option has a private set of pseudo terminal indices. This option is mainly used to support containers in the Linux kernel. It is implemented in Linux kernel versions starting with 2.6.29. Further, this mount option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. To use this option effectively, /dev/ptmx must be a symbolic link to pts/ptmx. See Documentation/filesystems/devpts.txt in the Linux kernel source tree for details. ptmxmode=value Set the mode for the new ptmx device node in the devpts filesystem. With the support for multiple instances of devpts (see newinstance option above), each instance has a private ptmx node in the root of the devpts filesystem (typically /dev/pts/ptmx). For compatibility with older versions of the kernel, the default mode of the new ptmx node is 0000. ptmxmode=value specifies a more useful mode for the ptmx node and is highly recommended when the newinstance option is specified. This option is only implemented in Linux kernel versions starting with 2.6.29. Further, this option is valid only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configuration. Mount options for fat (Note: fat is not a separate filesystem, but a common part of the msdos, umsdos and vfat filesystems.) blocksize={512|1024|2048} Set blocksize (default 512). This option is obsolete. uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. dmask=value Set the umask applied to directories only. The default is the umask of the current process. The value is given in octal. fmask=value Set the umask applied to regular files only. The default is the umask of the current process. The value is given in octal. allow_utime=value This option controls the permission check of mtime/atime. 20 If current process is in group of files group ID, you can change timestamp. 2 Other users can change timestamp. The default is set from 'dmask' option. (If the directory is writable, utime(2) is also allowed. I.e. ~dmask & 022) Normally utime(2) checks that the current process is owner of the file, or that it has the CAP_FOWNER capability. But FAT filesystems dont have UID/GID on disk, so the normal check is too inflexible. With this option you can relax it. check=value Three different levels of pickiness can be chosen: r[elaxed] Upper and lower case are accepted and equivalent, long name parts are truncated (e.g. verylongname.foobar becomes verylong.foo), leading and embedded spaces are accepted in each name part (name and extension). n[ormal] Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are rejected. This is the default. s[trict] Like "normal", but names that contain long parts or special characters that are sometimes used on Linux but are not accepted by MS-DOS (+, =, etc.) are rejected. codepage=value Sets the codepage for converting to shortname characters on FAT and VFAT filesystems. By default, codepage 437 is used. conv=mode This option is obsolete and may fail or be ignored. cvf_format=module Forces the driver to use the CVF (Compressed Volume File) module cvf_module instead of auto-detection. If the kernel supports kmod, the cvf_format=xxx option also controls on-demand CVF module loading. This option is obsolete. cvf_option=option Option passed to the CVF module. This option is obsolete. debug Turn on the debug flag. A version string and a list of filesystem parameters will be printed (these data are also printed if the parameters appear to be inconsistent). discard If set, causes discard/TRIM commands to be issued to the block device when blocks are freed. This is useful for SSD devices and sparse/thinly-provisioned LUNs. dos1xfloppy If set, use a fallback default BIOS Parameter Block configuration, determined by backing device size. These static parameters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images. errors={panic|continue|remount-ro} Specify FAT behavior on critical errors: panic, continue without doing anything, or remount the partition in read-only mode (default behavior). fat={12|16|32} Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT type detection routine. Use with caution! iocharset=value Character set to use for converting between 8 bit characters and 16 bit Unicode characters. The default is iso8859-1. Long filenames are stored on disk in Unicode format. nfs={stale_rw|nostale_ro} Enable this only if you want to export the FAT filesystem over NFS. stale_rw: This option maintains an index (cache) of directory inodes which is used by the nfs-related code to improve look-ups. Full file operations (read/write) over NFS are supported but with cache eviction at NFS server, this could result in spurious ESTALE errors. nostale_ro: This option bases the inode number and file handle on the on-disk location of a file in the FAT directory entry. This ensures that ESTALE will not be returned after a file is evicted from the inode cache. However, it means that operations such as rename, create and unlink could cause file handles that previously pointed at one file to point at a different file, potentially causing data corruption. For this reason, this option also mounts the filesystem readonly. To maintain backward compatibility, -o nfs is also accepted, defaulting to stale_rw. tz=UTC This option disables the conversion of timestamps between local time (as used by Windows on FAT) and UTC (which Linux uses internally). This is particularly useful when mounting devices (like digital cameras) that are set to UTC in order to avoid the pitfalls of local time. time_offset=minutes Set offset for conversion of timestamps from local time used by FAT to UTC. I.e., minutes will be subtracted from each timestamp to convert it to UTC used internally by Linux. This is useful when the time zone set in the kernel via settimeofday(2) is not the time zone used by the filesystem. Note that this option still does not provide correct time stamps in all cases in presence of DST - time stamps in a different DST setting will be off by one hour. quiet Turn on the quiet flag. Attempts to chown or chmod files do not return errors, although they fail. Use with caution! rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO of the directory will just be ignored, and is used only by applications as a flag (e.g. its set for the customized folder). If you want to use ATTR_RO as read-only flag even for the directory, set this option. showexec If set, the execute permission bits of the file will be allowed only if the extension part of the name is .EXE, .COM, or .BAT. Not set by default. sys_immutable If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux. Not set by default. flush If set, the filesystem will try to flush to disk more early than normal. Not set by default. usefree Use the "free clusters" value stored on FSINFO. Itll be used to determine number of free clusters without scanning disk. But its not used by default, because recent Windows dont update it correctly in some case. If you are sure the "free clusters" on FSINFO is correct, by this option you can avoid scanning disk. dots, nodots, dotsOK=[yes|no] Various misguided attempts to force Unix or DOS conventions onto a FAT filesystem. Mount options for hfs creator=cccc, type=cccc Set the creator/type values as shown by the MacOS finder used for creating new files. Default values: '????'. uid=n, gid=n Set the owner and group of all files. (Default: the UID and GID of the current process.) dir_umask=n, file_umask=n, umask=n Set the umask used for all directories, all regular files, or all files and directories. Defaults to the umask of the current process. session=n Select the CDROM session to mount. Defaults to leaving that decision to the CDROM driver. This option will fail with anything but a CDROM as underlying device. part=n Select partition number n from the device. Only makes sense for CDROMs. Defaults to not parsing the partition table at all. quiet Dont complain about invalid mount options. Mount options for hpfs uid=value and gid=value Set the owner and group of all files. (Default: the UID and GID of the current process.) umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. case={lower|asis} Convert all files names to lower case, or leave them. (Default: case=lower.) conv=mode This option is obsolete and may fail or being ignored. nocheck Do not abort mounting when certain consistency checks fail. Mount options for iso9660 ISO 9660 is a standard describing a filesystem structure to be used on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the udf filesystem.) Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like restrictions on filename length), and in addition all characters are in upper case. Also there is no field for file ownership, protection, number of links, provision for block/character devices, etc. Rock Ridge is an extension to iso9660 that provides all of these UNIX-like features. Basically there are extensions to each directory record that supply all of the additional information, and when Rock Ridge is in use, the filesystem is indistinguishable from a normal UNIX filesystem (except that it is read-only, of course). norock Disable the use of Rock Ridge extensions, even if available. Cf. map. nojoliet Disable the use of Microsoft Joliet extensions, even if available. Cf. map. check={r[elaxed]|s[trict]} With check=relaxed, a filename is first converted to lower case before doing the lookup. This is probably only meaningful together with norock and map=normal. (Default: check=strict.) uid=value and gid=value Give all files in the filesystem the indicated user or group id, possibly overriding the information found in the Rock Ridge extensions. (Default: uid=0,gid=0.) map={n[ormal]|o[ff]|a[corn]} For non-Rock Ridge volumes, normal name translation maps upper to lower case ASCII, drops a trailing ';1', and converts ';' to '.'. With map=off no name translation is done. See norock. (Default: map=normal.) map=acorn is like map=normal but also apply Acorn extensions if present. mode=value For non-Rock Ridge volumes, give all files the indicated mode. (Default: read and execute permission for everybody.) Octal mode values require a leading 0. unhide Also show hidden and associated files. (If the ordinary files and the associated or hidden files have the same filenames, this may make the ordinary files inaccessible.) block={512|1024|2048} Set the block size to the indicated value. (Default: block=1024.) conv=mode This option is obsolete and may fail or being ignored. cruft If the high byte of the file length contains other garbage, set this mount option to ignore the high order bits of the file length. This implies that a file cannot be larger than 16 MB. session=x Select number of session on a multisession CD. sbsector=xxx Session begins from sector xxx. The following options are the same as for vfat and specifying them only makes sense when using discs encoded using Microsofts Joliet extensions. iocharset=value Character set to use for converting 16 bit Unicode characters on CD to 8 bit characters. The default is iso8859-1. utf8 Convert 16 bit Unicode characters on CD to UTF-8. Mount options for jfs iocharset=name Character set to use for converting from Unicode to ASCII. The default is to do no conversion. Use iocharset=utf8 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in the kernel .config file. resize=value Resize the volume to value blocks. JFS only supports growing a volume, not shrinking it. This option is only valid during a remount, when the volume is mounted read-write. The resize keyword with no value will grow the volume to the full size of the partition. nointegrity Do not write to the journal. The primary use of this option is to allow for higher performance when restoring a volume from backup media. The integrity of the volume is not guaranteed if the system abnormally ends. integrity Default. Commit metadata changes to the journal. Use this option to remount a volume where the nointegrity option was previously specified in order to restore normal behavior. errors={continue|remount-ro|panic} Define the behavior when an error is encountered. (Either ignore errors and just mark the filesystem erroneous and continue, or remount the filesystem read-only, or panic and halt the system.) noquota|quota|usrquota|grpquota These options are accepted but ignored. Mount options for msdos See mount options for fat. If the msdos filesystem detects an inconsistency, it reports an error and sets the file system read-only. The filesystem can be made writable again by remounting it. Mount options for ncpfs Just like nfs, the ncpfs implementation expects a binary argument (a struct ncp_mount_data) to the mount(2) system call. This argument is constructed by ncpmount(8) and the current version of mount (2.12) does not know anything about ncpfs. Mount options for ntfs iocharset=name Character set to use when returning file names. Unlike VFAT, NTFS suppresses names that contain nonconvertible characters. Deprecated. nls=name New name for the option earlier called iocharset. utf8 Use UTF-8 for converting file names. uni_xlate={0|1|2} For 0 (or 'no' or 'false'), do not use escape sequences for unknown Unicode characters. For 1 (or 'yes' or 'true') or 2, use vfat-style 4-byte escape sequences starting with ":". Here 2 gives a little-endian encoding and 1 a byteswapped bigendian encoding. posix=[0|1] If enabled (posix=1), the filesystem distinguishes between upper and lower case. The 8.3 alias names are presented as hard links instead of being suppressed. This option is obsolete. uid=value, gid=value and umask=value Set the file permission on the filesystem. The umask value is given in octal. By default, the files are owned by root and not readable by somebody else. Mount options for overlay Since Linux 3.18 the overlay pseudo filesystem implements a union mount for other filesystems. An overlay filesystem combines two filesystems - an upper filesystem and a lower filesystem. When a name exists in both filesystems, the object in the upper filesystem is visible while the object in the lower filesystem is either hidden or, in the case of directories, merged with the upper object. The lower filesystem can be any filesystem supported by Linux and does not need to be writable. The lower filesystem can even be another overlayfs. The upper filesystem will normally be writable and if it is it must support the creation of trusted.* extended attributes, and must provide a valid d_type in readdir responses, so NFS is not suitable. A read-only overlay of two read-only filesystems may use any filesystem type. The options lowerdir and upperdir are combined into a merged directory by using: mount -t overlay overlay \ -olowerdir=/lower,upperdir=/upper,workdir=/work /merged lowerdir=directory Any filesystem, does not need to be on a writable filesystem. upperdir=directory The upperdir is normally on a writable filesystem. workdir=directory The workdir needs to be an empty directory on the same filesystem as upperdir. userxattr Use the "user.overlay." xattr namespace instead of "trusted.overlay.". This is useful for unprivileged mounting of overlayfs. redirect_dir={on|off|follow|nofollow} If the redirect_dir feature is enabled, then the directory will be copied up (but not the contents). Then the "{trusted|user}.overlay.redirect" extended attribute is set to the path of the original location from the root of the overlay. Finally the directory is moved to the new location. on Redirects are enabled. off Redirects are not created and only followed if "redirect_always_follow" feature is enabled in the kernel/module config. follow Redirects are not created, but followed. nofollow Redirects are not created and not followed (equivalent to "redirect_dir=off" if "redirect_always_follow" feature is not enabled). index={on|off} Inode index. If this feature is disabled and a file with multiple hard links is copied up, then this will "break" the link. Changes will not be propagated to other names referring to the same inode. uuid={on|off} Can be used to replace UUID of the underlying filesystem in file handles with null, and effectively disable UUID checks. This can be useful in case the underlying disk is copied and the UUID of this copy is changed. This is only applicable if all lower/upper/work directories are on the same filesystem, otherwise it will fallback to normal behaviour. nfs_export={on|off} When the underlying filesystems supports NFS export and the "nfs_export" feature is enabled, an overlay filesystem may be exported to NFS. With the "nfs_export" feature, on copy_up of any lower object, an index entry is created under the index directory. The index entry name is the hexadecimal representation of the copy up origin file handle. For a non-directory object, the index entry is a hard link to the upper inode. For a directory object, the index entry has an extended attribute "{trusted|user}.overlay.upper" with an encoded file handle of the upper directory inode. When encoding a file handle from an overlay filesystem object, the following rules apply For a non-upper object, encode a lower file handle from lower inode For an indexed object, encode a lower file handle from copy_up origin For a pure-upper object and for an existing non-indexed upper object, encode an upper file handle from upper inode The encoded overlay file handle includes Header including path type information (e.g. lower/upper) UUID of the underlying filesystem Underlying filesystem encoding of underlying inode This encoding format is identical to the encoding format of file handles that are stored in extended attribute "{trusted|user}.overlay.origin". When decoding an overlay file handle, the following steps are followed Find underlying layer by UUID and path type information. Decode the underlying filesystem file handle to underlying dentry. For a lower file handle, lookup the handle in index directory by name. If a whiteout is found in index, return ESTALE. This represents an overlay object that was deleted after its file handle was encoded. For a non-directory, instantiate a disconnected overlay dentry from the decoded underlying dentry, the path type and index inode, if found. For a directory, use the connected underlying decoded dentry, path type and index, to lookup a connected overlay dentry. Decoding a non-directory file handle may return a disconnected dentry. copy_up of that disconnected dentry will create an upper index entry with no upper alias. When overlay filesystem has multiple lower layers, a middle layer directory may have a "redirect" to lower directory. Because middle layer "redirects" are not indexed, a lower file handle that was encoded from the "redirect" origin directory, cannot be used to find the middle or upper layer directory. Similarly, a lower file handle that was encoded from a descendant of the "redirect" origin directory, cannot be used to reconstruct a connected overlay path. To mitigate the cases of directories that cannot be decoded from a lower file handle, these directories are copied up on encode and encoded as an upper file handle. On an overlay filesystem with no upper layer this mitigation cannot be used NFS export in this setup requires turning off redirect follow (e.g. "redirect_dir=nofollow"). The overlay filesystem does not support non-directory connectable file handles, so exporting with the subtree_check exportfs configuration will cause failures to lookup files over NFS. When the NFS export feature is enabled, all directory index entries are verified on mount time to check that upper file handles are not stale. This verification may cause significant overhead in some cases. Note: the mount options index=off,nfs_export=on are conflicting for a read-write mount and will result in an error. xino={on|off|auto} The "xino" feature composes a unique object identifier from the real object st_ino and an underlying fsid index. The "xino" feature uses the high inode number bits for fsid, because the underlying filesystems rarely use the high inode number bits. In case the underlying inode number does overflow into the high xino bits, overlay filesystem will fall back to the non xino behavior for that inode. For a detailed description of the effect of this option please refer to https://docs.kernel.org/filesystems/overlayfs.html metacopy={on|off} When metadata only copy up feature is enabled, overlayfs will only copy up metadata (as opposed to whole file), when a metadata specific operation like chown/chmod is performed. Full file will be copied up later when file is opened for WRITE operation. In other words, this is delayed data copy up operation and data is copied up when there is a need to actually modify data. volatile Volatile mounts are not guaranteed to survive a crash. It is strongly recommended that volatile mounts are only used if data written to the overlay can be recreated without significant effort. The advantage of mounting with the "volatile" option is that all forms of sync calls to the upper filesystem are omitted. In order to avoid a giving a false sense of safety, the syncfs (and fsync) semantics of volatile mounts are slightly different than that of the rest of VFS. If any writeback error occurs on the upperdirs filesystem after a volatile mount takes place, all sync functions will return an error. Once this condition is reached, the filesystem will not recover, and every subsequent sync call will return an error, even if the upperdir has not experience a new error since the last sync call. When overlay is mounted with "volatile" option, the directory "$workdir/work/incompat/volatile" is created. During next mount, overlay checks for this directory and refuses to mount if present. This is a strong indicator that user should throw away upper and work directories and create fresh one. In very limited cases where the user knows that the system has not crashed and contents of upperdir are intact, The "volatile" directory can be removed. Mount options for reiserfs Reiserfs is a journaling filesystem. conv Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem, using the 3.6 format for newly created objects. This filesystem will no longer be compatible with reiserfs 3.5 tools. hash={rupasov|tea|r5|detect} Choose which hash function reiserfs will use to find files within directories. rupasov A hash invented by Yury Yu. Rupasov. It is fast and preserves locality, mapping lexicographically close file names to close hash values. This option should not be used, as it causes a high probability of hash collisions. tea A Davis-Meyer function implemented by Jeremy Fitzhardinge. It uses hash permuting bits in the name. It gets high randomness and, therefore, low probability of hash collisions at some CPU cost. This may be used if EHASHCOLLISION errors are experienced with the r5 hash. r5 A modified version of the rupasov hash. It is used by default and is the best choice unless the filesystem has huge directories and unusual file-name patterns. detect Instructs mount to detect which hash function is in use by examining the filesystem being mounted, and to write this information into the reiserfs superblock. This is only useful on the first mount of an old format filesystem. hashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. no_unhashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. noborder Disable the border allocator algorithm invented by Yury Yu. Rupasov. This may provide performance improvements in some situations. nolog Disable journaling. This will provide slight performance improvements in some situations at the cost of losing reiserfss fast recovery from crashes. Even with this option turned on, reiserfs still performs all journaling operations, save for actual writes into its journaling area. Implementation of nolog is a work in progress. notail By default, reiserfs stores small files and 'file tails' directly into its tree. This confuses some utilities such as lilo(8). This option is used to disable packing of files into the tree. replayonly Replay the transactions which are in the journal, but do not actually mount the filesystem. Mainly used by reiserfsck. resize=number A remount option which permits online expansion of reiserfs partitions. Instructs reiserfs to assume that the device has number blocks. This option is designed for use with devices which are under logical volume management (LVM). There is a special resizer utility which can be obtained from ftp://ftp.namesys.com/pub/reiserfsprogs. user_xattr Enable Extended User Attributes. See the attr(1) manual page. acl Enable POSIX Access Control Lists. See the acl(5) manual page. barrier=none / barrier=flush This disables / enables the use of write barriers in the journaling code. barrier=none disables, barrier=flush enables (default). This also requires an IO stack which can support barriers, and if reiserfs gets an error on a barrier write, it will disable barriers again with a warning. Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance penalty. If your disks are battery-backed in one way or another, disabling barriers may safely improve performance. Mount options for ubifs UBIFS is a flash filesystem which works on top of UBI volumes. Note that atime is not supported and is always turned off. The device name may be specified as ubiX_Y UBI device number X, volume number Y ubiY UBI device number 0, volume number Y ubiX:NAME UBI device number X, volume with name NAME ubi:NAME UBI device number 0, volume with name NAME Alternative ! separator may be used instead of :. The following mount options are available: bulk_read Enable bulk-read. VFS read-ahead is disabled because it slows down the filesystem. Bulk-Read is an internal optimization. Some flashes may read faster if the data are read at one go, rather than at several read requests. For example, OneNAND can do "read-while-load" if it reads more than one NAND page. no_bulk_read Do not bulk-read. This is the default. chk_data_crc Check data CRC-32 checksums. This is the default. no_chk_data_crc Do not check data CRC-32 checksums. With this option, the filesystem does not check CRC-32 checksum for data, but it does check it for the internal indexing information. This option only affects reading, not writing. CRC-32 is always calculated when writing the data. compr={none|lzo|zlib} Select the default compressor which is used when new files are written. It is still possible to read compressed files if mounted with the none option. Mount options for udf UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical Storage Technology Association, and is often used for DVD-ROM, frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, however, perfectly usable by itself on disk drives, flash drives and other block devices. See also iso9660. uid= Make all files in the filesystem belong to the given user. uid=forget can be specified independently of (or usually in addition to) uid=<user> and results in UDF not storing uids to the media. In fact the recorded uid is the 32-bit overflow uid -1 as defined by the UDF standard. The value is given as either <user> which is a valid user name or the corresponding decimal user id, or the special string "forget". gid= Make all files in the filesystem belong to the given group. gid=forget can be specified independently of (or usually in addition to) gid=<group> and results in UDF not storing gids to the media. In fact the recorded gid is the 32-bit overflow gid -1 as defined by the UDF standard. The value is given as either <group> which is a valid group name or the corresponding decimal group id, or the special string "forget". umask= Mask out the given permissions from all inodes read from the filesystem. The value is given in octal. mode= If mode= is set the permissions of all non-directory inodes read from the filesystem will be set to the given mode. The value is given in octal. dmode= If dmode= is set the permissions of all directory inodes read from the filesystem will be set to the given dmode. The value is given in octal. bs= Set the block size. Default value prior to kernel version 2.6.30 was 2048. Since 2.6.30 and prior to 4.11 it was logical device block size with fallback to 2048. Since 4.11 it is logical block size with fallback to any valid block size between logical device block size and 4096. For other details see the mkudffs(8) 2.0+ manpage, see the COMPATIBILITY and BLOCK SIZE sections. unhide Show otherwise hidden files. undelete Show deleted files in lists. adinicb Embed data in the inode. (default) noadinicb Dont embed data in the inode. shortad Use short UDF address descriptors. longad Use long UDF address descriptors. (default) nostrict Unset strict conformance. iocharset= Set the NLS character set. This requires kernel compiled with CONFIG_UDF_NLS option. utf8 Set the UTF-8 character set. Mount options for debugging and disaster recovery novrs Ignore the Volume Recognition Sequence and attempt to mount anyway. session= Select the session number for multi-session recorded optical media. (default= last session) anchor= Override standard anchor location. (default= 256) lastblock= Set the last block of the filesystem. Unused historical mount options that may be encountered and should be removed uid=ignore Ignored, use uid=<user> instead. gid=ignore Ignored, use gid=<group> instead. volume= Unimplemented and ignored. partition= Unimplemented and ignored. fileset= Unimplemented and ignored. rootdir= Unimplemented and ignored. Mount options for ufs ufstype=value UFS is a filesystem widely used in different operating systems. The problem are differences among implementations. Features of some implementations are undocumented, so its hard to recognize the type of ufs automatically. Thats why the user must specify the type of ufs by mount option. Possible values are: old Old format of ufs, this is the default, read only. (Dont forget to give the -r option.) 44bsd For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD). ufs2 Used in FreeBSD 5.x supported as read-write. 5xbsd Synonym for ufs2. sun For filesystems created by SunOS or Solaris on Sparc. sunx86 For filesystems created by Solaris on x86. hp For filesystems created by HP-UX, read-only. nextstep For filesystems created by NeXTStep (on NeXT station) (currently read only). nextstep-cd For NextStep CDROMs (block_size == 2048), read-only. openstep For filesystems created by OpenStep (currently read only). The same filesystem type is also used by macOS. onerror=value Set behavior on error: panic If an error is encountered, cause a kernel panic. [lock|umount|repair] These mount options dont do anything at present; when an error is encountered only a console message is printed. Mount options for umsdos See mount options for msdos. The dotsOK option is explicitly killed by umsdos. Mount options for vfat First of all, the mount options for fat are recognized. The dotsOK option is explicitly killed by vfat. Furthermore, there are uni_xlate Translate unhandled Unicode characters to special escaped sequences. This lets you backup and restore filenames that are created with any Unicode characters. Without this option, a '?' is used when no translation is possible. The escape character is ':' because it is otherwise invalid on the vfat filesystem. The escape sequence that gets used, where u is the Unicode character, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12). posix Allow two files with names that only differ in case. This option is obsolete. nonumtail First try to make a short name without sequence number, before trying name~num.ext. utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the console. It can be enabled for the filesystem with this option or disabled with utf8=0, utf8=no or utf8=false. If uni_xlate gets set, UTF8 gets disabled. shortname=mode Defines the behavior for creation and display of filenames which fit into 8.3 characters. If a long name for a file exists, it will always be the preferred one for display. There are four modes: lower Force the short name to lower case upon display; store a long name when the short name is not all upper case. win95 Force the short name to upper case upon display; store a long name when the short name is not all upper case. winnt Display the short name as is; store a long name when the short name is not all lower case or all upper case. mixed Display the short name as is; store a long name when the short name is not all upper case. This mode is the default since Linux 2.6.32. Mount options for usbfs devuid=uid and devgid=gid and devmode=mode Set the owner and group and mode of the device files in the usbfs filesystem (default: uid=gid=0, mode=0644). The mode is given in octal. busuid=uid and busgid=gid and busmode=mode Set the owner and group and mode of the bus directories in the usbfs filesystem (default: uid=gid=0, mode=0555). The mode is given in octal. listuid=uid and listgid=gid and listmode=mode Set the owner and group and mode of the file devices (default: uid=gid=0, mode=0444). The mode is given in octal. DM-VERITY SUPPORT top The device-mapper verity target provides read-only transparent integrity checking of block devices using kernel crypto API. The mount command can open the dm-verity device and do the integrity verification before the device filesystem is mounted. Requires libcryptsetup with in libmount (optionally via dlopen(3)). If libcryptsetup supports extracting the root hash of an already mounted device, existing devices will be automatically reused in case of a match. Mount options for dm-verity: verity.hashdevice=path Path to the hash tree device associated with the source volume to pass to dm-verity. verity.roothash=hex Hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothashfile. verity.roothashfile=path Path to file containing the hex-encoded hash of the root of verity.hashdevice. Mutually exclusive with verity.roothash. verity.hashoffset=offset If the hash tree device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the tree. verity.fecdevice=path Path to the Forward Error Correction (FEC) device associated with the source volume to pass to dm-verity. Optional. Requires kernel built with CONFIG_DM_VERITY_FEC. verity.fecoffset=offset If the FEC device is embedded in the source volume, offset (default: 0) is used by dm-verity to get to the FEC area. Optional. verity.fecroots=value Parity bytes for FEC (default: 2). Optional. verity.roothashsig=path Path to pkcs7(1ssl) signature of root hash hex string. Requires crypt_activate_by_signed_key() from cryptsetup and kernel built with CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG. For device reuse, signatures have to be either used by all mounts of a device or by none. Optional. verity.oncorruption=ignore|restart|panic Instruct the kernel to ignore, reboot or panic when corruption is detected. By default the I/O operation simply fails. Requires Linux 4.1 or newer, and libcrypsetup 2.3.4 or newer. Optional. Supported since util-linux v2.35. For example commands: mksquashfs /etc /tmp/etc.raw veritysetup format /tmp/etc.raw /tmp/etc.verity --root-hash-file=/tmp/etc.roothash openssl smime -sign -in /tmp/etc.roothash -nocerts -inkey private.key \ -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s mount -o verity.hashdevice=/tmp/etc.verity,verity.roothashfile=/tmp/etc.roothash,\ verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.raw /mnt create squashfs image from /etc directory, verity hash device and mount verified filesystem image to /mnt. The kernel will verify that the root hash is signed by a key from the kernel keyring if roothashsig is used. LOOP-DEVICE SUPPORT top One further possible type is a mount via the loop device. For example, the command mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3 will set up the loop device /dev/loop3 to correspond to the file /tmp/disk.img, and then mount this device on /mnt. If no explicit loop device is mentioned (but just an option '-o loop' is given), then mount will try to find some unused loop device and use that, for example mount /tmp/disk.img /mnt -o loop The mount command automatically creates a loop device from a regular file if a filesystem type is not specified or the filesystem is known for libblkid, for example: mount /tmp/disk.img /mnt mount -t ext4 /tmp/disk.img /mnt This type of mount knows about three options, namely loop, offset and sizelimit, that are really options to losetup(8). (These options can be used in addition to those specific to the filesystem type.) Since Linux 2.6.25 auto-destruction of loop devices is supported, meaning that any loop device allocated by mount will be freed by umount independently of /etc/mtab. You can also free a loop device by hand, using losetup -d or umount -d. Since util-linux v2.29, mount re-uses the loop device rather than initializing a new device if the same backing file is already used for some loop device with the same offset and sizelimit. This is necessary to avoid a filesystem corruption. EXIT STATUS top mount has the following exit status values (the bits can be ORed): 0 success 1 incorrect invocation or permissions 2 system error (out of memory, cannot fork, no more loop devices) 4 internal mount bug 8 user interrupt 16 problems writing or locking /etc/mtab 32 mount failure 64 some mount succeeded The command mount -a returns 0 (all succeeded), 32 (all failed), or 64 (some failed, some succeeded). EXTERNAL HELPERS top The syntax of external mount helpers is: /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t type.subtype] where the suffix is the filesystem type and the -sfnvoN options have the same meaning as the normal mount options. The -t option is used for filesystems with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs). The command mount does not pass the mount options unbindable, runbindable, private, rprivate, slave, rslave, shared, rshared, auto, noauto, comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers. All other options are used in a comma-separated list as an argument to the -o option. ENVIRONMENT top LIBMOUNT_FORCE_MOUNT2={always|never|auto} force to use classic mount(2) system call (requires support for new file descriptors based mount API). The default is auto; in this case, libmount tries to be smart and use classic mount(2) only for well-known issues. If the new mount API is unavailable, libmount can still use traditional mount(2), although LIBMOUNT_FORCE_MOUNT2 is set to never. LIBMOUNT_FSTAB=<path> overrides the default location of the fstab file (ignored for suid) LIBMOUNT_DEBUG=all enables libmount debug output LIBBLKID_DEBUG=all enables libblkid debug output LOOPDEV_DEBUG=all enables loop device setup debug output FILES top See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section above. /etc/fstab filesystem table /run/mount libmount private runtime directory /etc/mtab table of mounted filesystems or symlink to /proc/mounts /etc/mtab~ lock file (unused on systems with mtab symlink) /etc/mtab.tmp temporary file (unused on systems with mtab symlink) /etc/filesystems a list of filesystem types to try HISTORY top A mount command existed in Version 5 AT&T UNIX. BUGS top It is possible for a corrupted filesystem to cause a crash. Some Linux filesystems dont support -o sync and -o dirsync (the ext2, ext3, ext4, fat and vfat filesystems do support synchronous updates (a la BSD) when mounted with the sync option). The -o remount may not be able to change mount parameters (all ext2fs-specific parameters, except sb, are changeable with a remount, for example, but you cant change gid or umask for the fatfs). It is possible that the files /etc/mtab and /proc/mounts dont match on systems with a regular mtab file. The first file is based only on the mount command options, but the content of the second file also depends on the kernel and others settings (e.g. on a remote NFS server in certain cases the mount command may report unreliable information about an NFS mount point and the /proc/mount file usually contains more reliable information.) This is another reason to replace the mtab file with a symlink to the /proc/mounts file. Checking files on NFS filesystems referenced by file descriptors (i.e. the fcntl and ioctl families of functions) may lead to inconsistent results due to the lack of a consistency check in the kernel even if the noac mount option is used. The loop option with the offset or sizelimit options used may fail when using older kernels if the mount command cant confirm that the size of the block device has been configured as requested. This situation can be worked around by using the losetup(8) command manually before calling mount with the configured loop device. AUTHORS top Karel Zak <kzak@redhat.com> SEE ALSO top mount(2), umount(2), filesystems(5), fstab(5), nfs(5), xfs(5), mount_namespaces(7), xattr(7), e2label(8), findmnt(8), losetup(8), lsblk(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8), umount(8), xfs_admin(8) REPORTING BUGS top For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY top The mount command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at https://www.kernel.org/pub/linux/utils/util-linux/. If you have a bug report for this manual page, send it to util-linux@vger.kernel.org. This page was obtained from the project's upstream Git repository git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org util-linux 2.39.594-1e0ad 2023-08-25 MOUNT(8) Pages that refer to this page: eject(1), fusermount3(1), homectl(1), mountpoint(1), quotasync(1), systemd-dissect(1), systemd-mount(1), unshare(1), chown(2), fcntl(2), fsync(2), ioctl_iflags(2), mount(2), open(2), open_by_handle_at(2), umount(2), getmntent(3), getsubopt(3), fd(4), hd(4), loop(4), ram(4), autofs(5), ext4(5), filesystems(5), fstab(5), lxc.container.conf(5), nfs(5), nfsmount.conf(5), proc(5), repart.d(5), systemd.automount(5), systemd.exec(5), systemd.mount(5), tmpfs(5), xfs(5), bootparam(7), fanotify(7), file-hierarchy(7), hier(7), inode(7), man-pages(7), mount_namespaces(7), spufs(7), automount(8), blkid(8), btrfs-subvolume(8), e4crypt(8), e4defrag(8), findmnt(8), fsck.cramfs(8), fsck.xfs(8), fsfreeze(8), fstrim(8), lsof(8), mkfs.cramfs(8), mount(8), mount.fuse3(8), mount.nfs(8), pam_namespace(8), pivot_root(8), quotaon(8), swapon(8), switch_root(8), systemd-remount-fs.service(8), tune2fs(8), umount(8), wipefs(8), xfs_admin(8), xfs_db(8), xfs_freeze(8), xfs_growfs(8), xfs_info(8), xfs_logprint(8), xfs_rtcp(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. readlink(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training readlink(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON READLINK(1) User Commands READLINK(1) NAME top readlink - print resolved symbolic links or canonical file names SYNOPSIS top readlink [OPTION]... FILE... DESCRIPTION top Note realpath(1) is the preferred command to use for canonicalization functionality. Print value of a symbolic link or canonical file name -f, --canonicalize canonicalize by following every symlink in every component of the given name recursively; all but the last component must exist -e, --canonicalize-existing canonicalize by following every symlink in every component of the given name recursively, all components must exist -m, --canonicalize-missing canonicalize by following every symlink in every component of the given name recursively, without requirements on components existence -n, --no-newline do not output the trailing delimiter -q, --quiet -s, --silent suppress most error messages (on by default) -v, --verbose report error messages -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit AUTHOR top Written by Dmitry V. Levin. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top readlink(2), realpath(1), realpath(3) Full documentation <https://www.gnu.org/software/coreutils/readlink> or available locally via: info '(coreutils) readlink invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 READLINK(1) Pages that refer to this page: basename(1), dirname(1), dpkg-realpath(1), realpath(1), unshare(1), mount(2), readlink(2), unshare(2), namespaces(7), mount(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if a drive with UUID "$UUID" is mounted Bash Command:<START>mount | grep $(readlink -f /dev/disk/by-uuid/$UUID )<END>

Check if content of all top-level *.txt files in the current directory contain only unique lines

cat *.txt | sort | sort -u -c

['cat', 'sort']

Output a Bash command to accomplish the following task. Task: Check if content of all top-level *.txt files in the current directory contain only unique lines Bash Command:<START>cat *.txt | sort | sort -u -c<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # cat\n\n> Print and concatenate files.\n> More information: <https://www.gnu.org/software/coreutils/cat>.\n\n- Print the contents of a file to `stdout`:\n\n`cat {{path/to/file}}`\n\n- Concatenate several files into an output file:\n\n`cat {{path/to/file1 path/to/file2 ...}} > {{path/to/output_file}}`\n\n- Append several files to an output file:\n\n`cat {{path/to/file1 path/to/file2 ...}} >> {{path/to/output_file}}`\n\n- Write `stdin` to a file:\n\n`cat - > {{path/to/file}}`\n\n- [n]umber all output lines:\n\n`cat -n {{path/to/file}}`\n\n- Display non-printable and whitespace characters (with `M-` prefix if non-ASCII):\n\n`cat -v -t -e {{path/to/file}}`\n # sort\n\n> Sort lines of text files.\n> More information: <https://www.gnu.org/software/coreutils/sort>.\n\n- Sort a file in ascending order:\n\n`sort {{path/to/file}}`\n\n- Sort a file in descending order:\n\n`sort --reverse {{path/to/file}}`\n\n- Sort a file in case-insensitive way:\n\n`sort --ignore-case {{path/to/file}}`\n\n- Sort a file using numeric rather than alphabetic order:\n\n`sort --numeric-sort {{path/to/file}}`\n\n- Sort `/etc/passwd` by the 3rd field of each line numerically, using ":" as a field separator:\n\n`sort --field-separator={{:}} --key={{3n}} {{/etc/passwd}}`\n\n- Sort a file preserving only unique lines:\n\n`sort --unique {{path/to/file}}`\n\n- Sort a file, printing the output to the specified output file (can be used to sort a file in-place):\n\n`sort --output={{path/to/file}} {{path/to/file}}`\n\n- Sort numbers with exponents:\n\n`sort --general-numeric-sort {{path/to/file}}`\n Task: Check if content of all top-level *.txt files in the current directory contain only unique lines Bash Command:<START>cat *.txt | sort | sort -u -c<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: cat(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training cat(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON CAT(1) User Commands CAT(1) NAME top cat - concatenate files and print on the standard output SYNOPSIS top cat [OPTION]... [FILE]... DESCRIPTION top Concatenate FILE(s) to standard output. With no FILE, or when FILE is -, read standard input. -A, --show-all equivalent to -vET -b, --number-nonblank number nonempty output lines, overrides -n -e equivalent to -vE -E, --show-ends display $ at end of each line -n, --number number all output lines -s, --squeeze-blank suppress repeated empty output lines -t equivalent to -vT -T, --show-tabs display TAB characters as ^I -u (ignored) -v, --show-nonprinting use ^ and M- notation, except for LFD and TAB --help display this help and exit --version output version information and exit EXAMPLES top cat f - g Output f's contents, then standard input, then g's contents. cat Copy standard input to standard output. AUTHOR top Written by Torbjorn Granlund and Richard M. Stallman. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top tac(1) Full documentation <https://www.gnu.org/software/coreutils/cat> or available locally via: info '(coreutils) cat invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 CAT(1) Pages that refer to this page: pmlogrewrite(1), pv(1), systemd-socket-activate(1), tac(1), ul(1), proc(5), cpuset(7), time_namespaces(7), readprofile(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sort(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sort(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON SORT(1) User Commands SORT(1) NAME top sort - sort lines of text files SYNOPSIS top sort [OPTION]... [FILE]... sort [OPTION]... --files0-from=F DESCRIPTION top Write sorted concatenation of all FILE(s) to standard output. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. Ordering options: -b, --ignore-leading-blanks ignore leading blanks -d, --dictionary-order consider only blanks and alphanumeric characters -f, --ignore-case fold lower case to upper case characters -g, --general-numeric-sort compare according to general numerical value -i, --ignore-nonprinting consider only printable characters -M, --month-sort compare (unknown) < 'JAN' < ... < 'DEC' -h, --human-numeric-sort compare human readable numbers (e.g., 2K 1G) -n, --numeric-sort compare according to string numerical value -R, --random-sort shuffle, but group identical keys. See shuf(1) --random-source=FILE get random bytes from FILE -r, --reverse reverse the result of comparisons --sort=WORD sort according to WORD: general-numeric -g, human-numeric -h, month -M, numeric -n, random -R, version -V -V, --version-sort natural sort of (version) numbers within text Other options: --batch-size=NMERGE merge at most NMERGE inputs at once; for more use temp files -c, --check, --check=diagnose-first check for sorted input; do not sort -C, --check=quiet, --check=silent like -c, but do not report first bad line --compress-program=PROG compress temporaries with PROG; decompress them with PROG -d --debug annotate the part of the line used to sort, and warn about questionable usage to stderr --files0-from=F read input from the files specified by NUL-terminated names in file F; If F is - then read names from standard input -k, --key=KEYDEF sort via a key; KEYDEF gives location and type -m, --merge merge already sorted files; do not sort -o, --output=FILE write result to FILE instead of standard output -s, --stable stabilize sort by disabling last-resort comparison -S, --buffer-size=SIZE use SIZE for main memory buffer -t, --field-separator=SEP use SEP instead of non-blank to blank transition -T, --temporary-directory=DIR use DIR for temporaries, not $TMPDIR or /tmp; multiple options specify multiple directories --parallel=N change the number of sorts run concurrently to N -u, --unique with -c, check for strict ordering; without -c, output only the first of an equal run -z, --zero-terminated line delimiter is NUL, not newline --help display this help and exit --version output version information and exit KEYDEF is F[.C][OPTS][,F[.C][OPTS]] for start and stop position, where F is a field number and C a character position in the field; both are origin 1, and the stop position defaults to the line's end. If neither -t nor -b is in effect, characters in a field are counted from the beginning of the preceding whitespace. OPTS is one or more single-letter ordering options [bdfgiMhnRrV], which override global ordering options for that key. If no key is given, use the entire line as the key. Use --debug to diagnose incorrect key usage. SIZE may be followed by the following multiplicative suffixes: % 1% of memory, b 1, K 1024 (default), and so on for M, G, T, P, E, Z, Y, R, Q. *** WARNING *** The locale specified by the environment affects sort order. Set LC_ALL=C to get the traditional sort order that uses native byte values. AUTHOR top Written by Mike Haertel and Paul Eggert. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top shuf(1), uniq(1) Full documentation <https://www.gnu.org/software/coreutils/sort> or available locally via: info '(coreutils) sort invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 SORT(1) Pages that refer to this page: column(1), grep(1), look(1), prlimit(1), ps(1), uniq(1), qsort(3), environ(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if content of all top-level *.txt files in the current directory contain only unique lines Bash Command:<START>cat *.txt | sort | sort -u -c<END>

Check if directory $some_dir is empty

find "`echo "$some_dir"`" -maxdepth 0 -empty

['find', 'echo']

Output a Bash command to accomplish the following task. Task: Check if directory $some_dir is empty Bash Command:<START>find "`echo "$some_dir"`" -maxdepth 0 -empty<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # echo\n\n> Print given arguments.\n> More information: <https://www.gnu.org/software/coreutils/echo>.\n\n- Print a text message. Note: quotes are optional:\n\n`echo "{{Hello World}}"`\n\n- Print a message with environment variables:\n\n`echo "{{My path is $PATH}}"`\n\n- Print a message without the trailing newline:\n\n`echo -n "{{Hello World}}"`\n\n- Append a message to the file:\n\n`echo "{{Hello World}}" >> {{file.txt}}`\n\n- Enable interpretation of backslash escapes (special characters):\n\n`echo -e "{{Column 1\tColumn 2}}"`\n\n- Print the exit status of the last executed command (Note: In Windows Command Prompt and PowerShell the equivalent commands are `echo %errorlevel%` and `$lastexitcode` respectively):\n\n`echo $?`\n Task: Check if directory $some_dir is empty Bash Command:<START>find "`echo "$some_dir"`" -maxdepth 0 -empty<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. echo(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training echo(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON ECHO(1) User Commands ECHO(1) NAME top echo - display a line of text SYNOPSIS top echo [SHORT-OPTION]... [STRING]... echo LONG-OPTION DESCRIPTION top Echo the STRING(s) to standard output. -n do not output the trailing newline -e enable interpretation of backslash escapes -E disable interpretation of backslash escapes (default) --help display this help and exit --version output version information and exit If -e is in effect, the following sequences are recognized: \\ backslash \a alert (BEL) \b backspace \c produce no further output \e escape \f form feed \n new line \r carriage return \t horizontal tab \v vertical tab \0NNN byte with octal value NNN (1 to 3 digits) \xHH byte with hexadecimal value HH (1 to 2 digits) NOTE: your shell may have its own version of echo, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports. NOTE: printf(1) is a preferred alternative, which does not have issues outputting option-like strings. AUTHOR top Written by Brian Fox and Chet Ramey. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top printf(1) Full documentation <https://www.gnu.org/software/coreutils/echo> or available locally via: info '(coreutils) echo invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 ECHO(1) Pages that refer to this page: ldapcompare(1), systemd-ask-password(1), systemd-run(1), cpuset(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if directory $some_dir is empty Bash Command:<START>find "`echo "$some_dir"`" -maxdepth 0 -empty<END>

Check if process ID 1 exists (init or systemd) and current user has permission to send it signals.

kill -0 1

['kill']

Output a Bash command to accomplish the following task. Task: Check if process ID 1 exists (init or systemd) and current user has permission to send it signals. Bash Command:<START>kill -0 1<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # kill\n\n> Sends a signal to a process, usually related to stopping the process.\n> All signals except for SIGKILL and SIGSTOP can be intercepted by the process to perform a clean exit.\n> More information: <https://manned.org/kill>.\n\n- Terminate a program using the default SIGTERM (terminate) signal:\n\n`kill {{process_id}}`\n\n- List signal values and their corresponding names (to be used without the `SIG` prefix):\n\n`kill -{{L|-table}}`\n\n- Terminate a background job:\n\n`kill %{{job_id}}`\n\n- Terminate a program using the SIGHUP (hang up) signal. Many daemons will reload instead of terminating:\n\n`kill -{{1|HUP}} {{process_id}}`\n\n- Terminate a program using the SIGINT (interrupt) signal. This is typically initiated by the user pressing `Ctrl + C`:\n\n`kill -{{2|INT}} {{process_id}}`\n\n- Signal the operating system to immediately terminate a program (which gets no chance to capture the signal):\n\n`kill -{{9|KILL}} {{process_id}}`\n\n- Signal the operating system to pause a program until a SIGCONT ("continue") signal is received:\n\n`kill -{{17|STOP}} {{process_id}}`\n\n- Send a `SIGUSR1` signal to all processes with the given GID (group id):\n\n`kill -{{SIGUSR1}} -{{group_id}}`\n Task: Check if process ID 1 exists (init or systemd) and current user has permission to send it signals. Bash Command:<START>kill -0 1<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: kill(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training Other versions of this page are provided by these projects: coreutils procps-ng kill(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | ARGUMENTS | OPTIONS | EXIT STATUS | NOTES | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY KILL(1) User Commands KILL(1) NAME top kill - terminate a process SYNOPSIS top kill [-signal|-s signal|-p] [-q value] [-a] [--timeout milliseconds signal] [--] pid|name... kill -l [number] | -L DESCRIPTION top The command kill sends the specified signal to the specified processes or process groups. If no signal is specified, the TERM signal is sent. The default action for this signal is to terminate the process. This signal should be used in preference to the KILL signal (number 9), since a process may install a handler for the TERM signal in order to perform clean-up steps before terminating in an orderly fashion. If a process does not terminate after a TERM signal has been sent, then the KILL signal may be used; be aware that the latter signal cannot be caught, and so does not give the target process the opportunity to perform any clean-up before terminating. Most modern shells have a builtin kill command, with a usage rather similar to that of the command described here. The --all, --pid, and --queue options, and the possibility to specify processes by command name, are local extensions. If signal is 0, then no actual signal is sent, but error checking is still performed. ARGUMENTS top The list of processes to be signaled can be a mixture of names and PIDs. pid Each pid can be expressed in one of the following ways: n where n is larger than 0. The process with PID n is signaled. 0 All processes in the current process group are signaled. -1 All processes with a PID larger than 1 are signaled. -n where n is larger than 1. All processes in process group n are signaled. When an argument of the form '-n' is given, and it is meant to denote a process group, either a signal must be specified first, or the argument must be preceded by a '--' option, otherwise it will be taken as the signal to send. name All processes invoked using this name will be signaled. OPTIONS top -s, --signal signal The signal to send. It may be given as a name or a number. -l, --list [number] Print a list of signal names, or convert the given signal number to a name. The signals can be found in /usr/include/linux/signal.h. -L, --table Similar to -l, but it will print signal names and their corresponding numbers. -a, --all Do not restrict the command-name-to-PID conversion to processes with the same UID as the present process. -p, --pid Only print the process ID (PID) of the named processes, do not send any signals. -r, --require-handler Do not send the signal if it is not caught in userspace by the signalled process. --verbose Print PID(s) that will be signaled with kill along with the signal. -q, --queue value Send the signal using sigqueue(3) rather than kill(2). The value argument is an integer that is sent along with the signal. If the receiving process has installed a handler for this signal using the SA_SIGINFO flag to sigaction(2), then it can obtain this data via the si_sigval field of the siginfo_t structure. --timeout milliseconds signal Send a signal defined in the usual way to a process, followed by an additional signal after a specified delay. The --timeout option causes kill to wait for a period defined in milliseconds before sending a follow-up signal to the process. This feature is implemented using the Linux kernel PID file descriptor feature in order to guarantee that the follow-up signal is sent to the same process or not sent if the process no longer exists. Note that the operating system may re-use PIDs and implementing an equivalent feature in a shell using kill and sleep would be subject to races whereby the follow-up signal might be sent to a different process that used a recycled PID. The --timeout option can be specified multiple times: the signals are sent sequentially with the specified timeouts. The --timeout option can be combined with the --queue option. As an example, the following command sends the signals QUIT, TERM and KILL in sequence and waits for 1000 milliseconds between sending the signals: kill --verbose --timeout 1000 TERM --timeout 1000 KILL \ --signal QUIT 12345 EXIT STATUS top kill has the following exit status values: 0 success 1 failure 64 partial success (when more than one process specified) NOTES top Although it is possible to specify the TID (thread ID, see gettid(2)) of one of the threads in a multithreaded process as the argument of kill, the signal is nevertheless directed to the process (i.e., the entire thread group). In other words, it is not possible to send a signal to an explicitly selected thread in a multithreaded process. The signal will be delivered to an arbitrarily selected thread in the target process that is not blocking the signal. For more details, see signal(7) and the description of CLONE_THREAD in clone(2). Various shells provide a builtin kill command that is preferred in relation to the kill(1) executable described by this manual. The easiest way to ensure one is executing the command described in this page is to use the full path when calling the command, for example: /bin/kill --version AUTHORS top Salvatore Valente <svalente@mit.edu>, Karel Zak <kzak@redhat.com> The original version was taken from BSD 4.4. SEE ALSO top bash(1), tcsh(1), sigaction(2), kill(2), sigqueue(3), signal(7) REPORTING BUGS top For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY top The kill command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at https://www.kernel.org/pub/linux/utils/util-linux/. If you have a bug report for this manual page, send it to util-linux@vger.kernel.org. This page was obtained from the project's upstream Git repository git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org util-linux 2.39.594-1e0ad 2023-07-19 KILL(1) Pages that refer to this page: fuser(1), kill(1), killall(1), pgrep(1), pmsignal(1), skill(1), tcpdump(1), timeout(1), xargs(1), kill(2), sigaction(2), signal(2), posix_spawn(3), signal(7), ldattach(8), lsof(8), systemd-coredump(8), tcpdump(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if process ID 1 exists (init or systemd) and current user has permission to send it signals. Bash Command:<START>kill -0 1<END>

Check if the $somedir directory is empty

find "$somedir" -maxdepth 0 -empty -exec echo {} is empty. \;

['find', 'echo']

Output a Bash command to accomplish the following task. Task: Check if the $somedir directory is empty Bash Command:<START>find "$somedir" -maxdepth 0 -empty -exec echo {} is empty. \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # echo\n\n> Print given arguments.\n> More information: <https://www.gnu.org/software/coreutils/echo>.\n\n- Print a text message. Note: quotes are optional:\n\n`echo "{{Hello World}}"`\n\n- Print a message with environment variables:\n\n`echo "{{My path is $PATH}}"`\n\n- Print a message without the trailing newline:\n\n`echo -n "{{Hello World}}"`\n\n- Append a message to the file:\n\n`echo "{{Hello World}}" >> {{file.txt}}`\n\n- Enable interpretation of backslash escapes (special characters):\n\n`echo -e "{{Column 1\tColumn 2}}"`\n\n- Print the exit status of the last executed command (Note: In Windows Command Prompt and PowerShell the equivalent commands are `echo %errorlevel%` and `$lastexitcode` respectively):\n\n`echo $?`\n Task: Check if the $somedir directory is empty Bash Command:<START>find "$somedir" -maxdepth 0 -empty -exec echo {} is empty. \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. echo(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training echo(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON ECHO(1) User Commands ECHO(1) NAME top echo - display a line of text SYNOPSIS top echo [SHORT-OPTION]... [STRING]... echo LONG-OPTION DESCRIPTION top Echo the STRING(s) to standard output. -n do not output the trailing newline -e enable interpretation of backslash escapes -E disable interpretation of backslash escapes (default) --help display this help and exit --version output version information and exit If -e is in effect, the following sequences are recognized: \\ backslash \a alert (BEL) \b backspace \c produce no further output \e escape \f form feed \n new line \r carriage return \t horizontal tab \v vertical tab \0NNN byte with octal value NNN (1 to 3 digits) \xHH byte with hexadecimal value HH (1 to 2 digits) NOTE: your shell may have its own version of echo, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports. NOTE: printf(1) is a preferred alternative, which does not have issues outputting option-like strings. AUTHOR top Written by Brian Fox and Chet Ramey. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top printf(1) Full documentation <https://www.gnu.org/software/coreutils/echo> or available locally via: info '(coreutils) echo invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 ECHO(1) Pages that refer to this page: ldapcompare(1), systemd-ask-password(1), systemd-run(1), cpuset(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if the $somedir directory is empty Bash Command:<START>find "$somedir" -maxdepth 0 -empty -exec echo {} is empty. \;<END>

Check if the contents of file "subset" is a subset of file "set"

comm -23 <(sort subset | uniq) <(sort set | uniq) | head -1

['head', 'set', 'sort', 'uniq', 'comm']

Output a Bash command to accomplish the following task. Task: Check if the contents of file "subset" is a subset of file "set" Bash Command:<START>comm -23 <(sort subset | uniq) <(sort set | uniq) | head -1<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # head\n\n> Output the first part of files.\n> More information: <https://www.gnu.org/software/coreutils/head>.\n\n- Output the first few lines of a file:\n\n`head --lines {{count}} {{path/to/file}}`\n\n- Output the first few bytes of a file:\n\n`head --bytes {{count}} {{path/to/file}}`\n\n- Output everything but the last few lines of a file:\n\n`head --lines -{{count}} {{path/to/file}}`\n\n- Output everything but the last few bytes of a file:\n\n`head --bytes -{{count}} {{path/to/file}}`\n # set\n\n> Toggle shell options or set the values of positional parameters.\n> More information: <https://manned.org/set.1posix>.\n\n- Display the names and values of shell variables:\n\n`set`\n\n- Export newly initialized variables to child processes:\n\n`set -a`\n\n- Write formatted messages to `stderr` when jobs finish:\n\n`set -b`\n\n- Write and edit text in the command line with `vi`-like keybindings (e.g. `yy`):\n\n`set -o {{vi}}`\n\n- Exit the shell when (some) commands fail:\n\n`set -e`\n # sort\n\n> Sort lines of text files.\n> More information: <https://www.gnu.org/software/coreutils/sort>.\n\n- Sort a file in ascending order:\n\n`sort {{path/to/file}}`\n\n- Sort a file in descending order:\n\n`sort --reverse {{path/to/file}}`\n\n- Sort a file in case-insensitive way:\n\n`sort --ignore-case {{path/to/file}}`\n\n- Sort a file using numeric rather than alphabetic order:\n\n`sort --numeric-sort {{path/to/file}}`\n\n- Sort `/etc/passwd` by the 3rd field of each line numerically, using ":" as a field separator:\n\n`sort --field-separator={{:}} --key={{3n}} {{/etc/passwd}}`\n\n- Sort a file preserving only unique lines:\n\n`sort --unique {{path/to/file}}`\n\n- Sort a file, printing the output to the specified output file (can be used to sort a file in-place):\n\n`sort --output={{path/to/file}} {{path/to/file}}`\n\n- Sort numbers with exponents:\n\n`sort --general-numeric-sort {{path/to/file}}`\n # uniq\n\n> Output the unique lines from a input or file.\n> Since it does not detect repeated lines unless they are adjacent, we need to sort them first.\n> More information: <https://www.gnu.org/software/coreutils/uniq>.\n\n- Display each line once:\n\n`sort {{path/to/file}} | uniq`\n\n- Display only unique lines:\n\n`sort {{path/to/file}} | uniq -u`\n\n- Display only duplicate lines:\n\n`sort {{path/to/file}} | uniq -d`\n\n- Display number of occurrences of each line along with that line:\n\n`sort {{path/to/file}} | uniq -c`\n\n- Display number of occurrences of each line, sorted by the most frequent:\n\n`sort {{path/to/file}} | uniq -c | sort -nr`\n # comm\n\n> Select or reject lines common to two files. Both files must be sorted.\n> More information: <https://www.gnu.org/software/coreutils/comm>.\n\n- Produce three tab-separated columns: lines only in first file, lines only in second file and common lines:\n\n`comm {{file1}} {{file2}}`\n\n- Print only lines common to both files:\n\n`comm -12 {{file1}} {{file2}}`\n\n- Print only lines common to both files, reading one file from `stdin`:\n\n`cat {{file1}} | comm -12 - {{file2}}`\n\n- Get lines only found in first file, saving the result to a third file:\n\n`comm -23 {{file1}} {{file2}} > {{file1_only}}`\n\n- Print lines only found in second file, when the files aren't sorted:\n\n`comm -13 <(sort {{file1}}) <(sort {{file2}})`\n Task: Check if the contents of file "subset" is a subset of file "set" Bash Command:<START>comm -23 <(sort subset | uniq) <(sort set | uniq) | head -1<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: head(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training head(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON HEAD(1) User Commands HEAD(1) NAME top head - output the first part of files SYNOPSIS top head [OPTION]... [FILE]... DESCRIPTION top Print the first 10 lines of each FILE to standard output. With more than one FILE, precede each with a header giving the file name. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. -c, --bytes=[-]NUM print the first NUM bytes of each file; with the leading '-', print all but the last NUM bytes of each file -n, --lines=[-]NUM print the first NUM lines instead of the first 10; with the leading '-', print all but the last NUM lines of each file -q, --quiet, --silent never print headers giving file names -v, --verbose always print headers giving file names -z, --zero-terminated line delimiter is NUL, not newline --help display this help and exit --version output version information and exit NUM may have a multiplier suffix: b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024, GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y, R, Q. Binary prefixes can be used, too: KiB=K, MiB=M, and so on. AUTHOR top Written by David MacKenzie and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top tail(1) Full documentation <https://www.gnu.org/software/coreutils/head> or available locally via: info '(coreutils) head invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 HEAD(1) Pages that refer to this page: tail(1) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. set(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training set(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT SET(1P) POSIX Programmer's Manual SET(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top set set or unset options and positional parameters SYNOPSIS top set [-abCefhmnuvx] [-o option] [argument...] set [+abCefhmnuvx] [+o option] [argument...] set -- [argument...] set -o set +o DESCRIPTION top If no options or arguments are specified, set shall write the names and values of all shell variables in the collation sequence of the current locale. Each name shall start on a separate line, using the format: "%s=%s\n", <name>, <value> The value string shall be written with appropriate quoting; see the description of shell quoting in Section 2.2, Quoting. The output shall be suitable for reinput to the shell, setting or resetting, as far as possible, the variables that are currently set; read-only variables cannot be reset. When options are specified, they shall set or unset attributes of the shell, as described below. When arguments are specified, they cause positional parameters to be set or unset, as described below. Setting or unsetting attributes and positional parameters are not necessarily related actions, but they can be combined in a single invocation of set. The set special built-in shall support the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines except that options can be specified with either a leading <hyphen-minus> (meaning enable the option) or <plus-sign> (meaning disable it) unless otherwise specified. Implementations shall support the options in the following list in both their <hyphen-minus> and <plus-sign> forms. These options can also be specified as options to sh. -a When this option is on, the export attribute shall be set for each variable to which an assignment is performed; see the Base Definitions volume of POSIX.12017, Section 4.23, Variable Assignment. If the assignment precedes a utility name in a command, the export attribute shall not persist in the current execution environment after the utility completes, with the exception that preceding one of the special built-in utilities causes the export attribute to persist after the built-in has completed. If the assignment does not precede a utility name in the command, or if the assignment is a result of the operation of the getopts or read utilities, the export attribute shall persist until the variable is unset. -b This option shall be supported if the implementation supports the User Portability Utilities option. It shall cause the shell to notify the user asynchronously of background job completions. The following message is written to standard error: "[%d]%c %s%s\n", <job-number>, <current>, <status>, <job-name> where the fields shall be as follows: <current> The character '+' identifies the job that would be used as a default for the fg or bg utilities; this job can also be specified using the job_id "%+" or "%%". The character '-' identifies the job that would become the default if the current default job were to exit; this job can also be specified using the job_id "%-". For other jobs, this field is a <space>. At most one job can be identified with '+' and at most one job can be identified with '-'. If there is any suspended job, then the current job shall be a suspended job. If there are at least two suspended jobs, then the previous job also shall be a suspended job. <job-number> A number that can be used to identify the process group to the wait, fg, bg, and kill utilities. Using these utilities, the job can be identified by prefixing the job number with '%'. <status> Unspecified. <job-name> Unspecified. When the shell notifies the user a job has been completed, it may remove the job's process ID from the list of those known in the current shell execution environment; see Section 2.9.3.1, Examples. Asynchronous notification shall not be enabled by default. -C (Uppercase C.) Prevent existing files from being overwritten by the shell's '>' redirection operator (see Section 2.7.2, Redirecting Output); the ">|" redirection operator shall override this noclobber option for an individual file. -e When this option is on, when any command fails (for any of the reasons listed in Section 2.8.1, Consequences of Shell Errors or by returning an exit status greater than zero), the shell immediately shall exit, as if by executing the exit special built-in utility with no arguments, with the following exceptions: 1. The failure of any individual command in a multi- command pipeline shall not cause the shell to exit. Only the failure of the pipeline itself shall be considered. 2. The -e setting shall be ignored when executing the compound list following the while, until, if, or elif reserved word, a pipeline beginning with the ! reserved word, or any command of an AND-OR list other than the last. 3. If the exit status of a compound command other than a subshell command was the result of a failure while -e was being ignored, then -e shall not apply to this command. This requirement applies to the shell environment and each subshell environment separately. For example, in: set -e; (false; echo one) | cat; echo two the false command causes the subshell to exit without executing echo one; however, echo two is executed because the exit status of the pipeline (false; echo one) | cat is zero. -f The shell shall disable pathname expansion. -h Locate and remember utilities invoked by functions as those functions are defined (the utilities are normally located when the function is executed). -m This option shall be supported if the implementation supports the User Portability Utilities option. All jobs shall be run in their own process groups. Immediately before the shell issues a prompt after completion of the background job, a message reporting the exit status of the background job shall be written to standard error. If a foreground job stops, the shell shall write a message to standard error to that effect, formatted as described by the jobs utility. In addition, if a job changes status other than exiting (for example, if it stops for input or output or is stopped by a SIGSTOP signal), the shell shall write a similar message immediately prior to writing the next prompt. This option is enabled by default for interactive shells. -n The shell shall read commands but does not execute them; this can be used to check for shell script syntax errors. An interactive shell may ignore this option. -o Write the current settings of the options to standard output in an unspecified format. +o Write the current option settings to standard output in a format that is suitable for reinput to the shell as commands that achieve the same options settings. -o option This option is supported if the system supports the User Portability Utilities option. It shall set various options, many of which shall be equivalent to the single option letters. The following values of option shall be supported: allexport Equivalent to -a. errexit Equivalent to -e. ignoreeof Prevent an interactive shell from exiting on end- of-file. This setting prevents accidental logouts when <control>D is entered. A user shall explicitly exit to leave the interactive shell. monitor Equivalent to -m. This option is supported if the system supports the User Portability Utilities option. noclobber Equivalent to -C (uppercase C). noglob Equivalent to -f. noexec Equivalent to -n. nolog Prevent the entry of function definitions into the command history; see Command History List. notify Equivalent to -b. nounset Equivalent to -u. verbose Equivalent to -v. vi Allow shell command line editing using the built- in vi editor. Enabling vi mode shall disable any other command line editing mode provided as an implementation extension. It need not be possible to set vi mode on for certain block-mode terminals. xtrace Equivalent to -x. -u When the shell tries to expand an unset parameter other than the '@' and '*' special parameters, it shall write a message to standard error and the expansion shall fail with the consequences specified in Section 2.8.1, Consequences of Shell Errors. -v The shell shall write its input to standard error as it is read. -x The shell shall write to standard error a trace for each command after it expands the command and before it executes it. It is unspecified whether the command that turns tracing off is traced. The default for all these options shall be off (unset) unless stated otherwise in the description of the option or unless the shell was invoked with them on; see sh. The remaining arguments shall be assigned in order to the positional parameters. The special parameter '#' shall be set to reflect the number of positional parameters. All positional parameters shall be unset before any new values are assigned. If the first argument is '-', the results are unspecified. The special argument "--" immediately following the set command name can be used to delimit the arguments if the first argument begins with '+' or '-', or to prevent inadvertent listing of all shell variables when there are no arguments. The command set -- without argument shall unset all positional parameters and set the special parameter '#' to zero. OPTIONS top See the DESCRIPTION. OPERANDS top See the DESCRIPTION. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top None. ASYNCHRONOUS EVENTS top Default. STDOUT top See the DESCRIPTION. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top 0 Successful completion. >0 An invalid option was specified, or an error occurred. CONSEQUENCES OF ERRORS top Default. The following sections are informative. APPLICATION USAGE top Application writers should avoid relying on set -e within functions. For example, in the following script: set -e start() { some_server echo some_server started successfully } start || echo >&2 some_server failed the -e setting is ignored within the function body (because the function is a command in an AND-OR list other than the last). Therefore, if some_server fails, the function carries on to echo "some_serverstartedsuccessfully", and the exit status of the function is zero (which means "some_serverfailed" is not output). EXAMPLES top Write out all variables and their values: set Set $1, $2, and $3 and set "$#" to 3: set c a b Turn on the -x and -v options: set -xv Unset all positional parameters: set -- Set $1 to the value of x, even if it begins with '-' or '+': set -- "$x" Set the positional parameters to the expansion of x, even if x expands with a leading '-' or '+': set -- $x RATIONALE top The set -- form is listed specifically in the SYNOPSIS even though this usage is implied by the Utility Syntax Guidelines. The explanation of this feature removes any ambiguity about whether the set -- form might be misinterpreted as being equivalent to set without any options or arguments. The functionality of this form has been adopted from the KornShell. In System V, set -- only unsets parameters if there is at least one argument; the only way to unset all parameters is to use shift. Using the KornShell version should not affect System V scripts because there should be no reason to issue it without arguments deliberately; if it were issued as, for example: set -- "$@" and there were in fact no arguments resulting from "$@", unsetting the parameters would have no result. The set + form in early proposals was omitted as being an unnecessary duplication of set alone and not widespread historical practice. The noclobber option was changed to allow set -C as well as the set -o noclobber option. The single-letter version was added so that the historical "$-" paradigm would not be broken; see Section 2.5.2, Special Parameters. The description of the -e option is intended to match the behavior of the 1988 version of the KornShell. The -h flag is related to command name hashing. See hash(1p). The following set flags were omitted intentionally with the following rationale: -k The -k flag was originally added by the author of the Bourne shell to make it easier for users of pre-release versions of the shell. In early versions of the Bourne shell the construct set name=value had to be used to assign values to shell variables. The problem with -k is that the behavior affects parsing, virtually precluding writing any compilers. To explain the behavior of -k, it is necessary to describe the parsing algorithm, which is implementation- defined. For example: set -k; echo name=value and: set -k echo name=value behave differently. The interaction with functions is even more complex. What is more, the -k flag is never needed, since the command line could have been reordered. -t The -t flag is hard to specify and almost never used. The only known use could be done with here-documents. Moreover, the behavior with ksh and sh differs. The reference page says that it exits after reading and executing one command. What is one command? If the input is date;date, sh executes both date commands while ksh does only the first. Consideration was given to rewriting set to simplify its confusing syntax. A specific suggestion was that the unset utility should be used to unset options instead of using the non- getopt()-able +option syntax. However, the conclusion was reached that the historical practice of using +option was satisfactory and that there was no compelling reason to modify such widespread historical practice. The -o option was adopted from the KornShell to address user needs. In addition to its generally friendly interface, -o is needed to provide the vi command line editing mode, for which historical practice yields no single-letter option name. (Although it might have been possible to invent such a letter, it was recognized that other editing modes would be developed and -o provides ample name space for describing such extensions.) Historical implementations are inconsistent in the format used for -o option status reporting. The +o format without an option- argument was added to allow portable access to the options that can be saved and then later restored using, for instance, a dot script. Historically, sh did trace the command set +x, but ksh did not. The ignoreeof setting prevents accidental logouts when the end- of-file character (typically <control>D) is entered. A user shall explicitly exit to leave the interactive shell. The set -m option was added to apply only to the UPE because it applies primarily to interactive use, not shell script applications. The ability to do asynchronous notification became available in the 1988 version of the KornShell. To have it occur, the user had to issue the command: trap "jobs -n" CLD The C shell provides two different levels of an asynchronous notification capability. The environment variable notify is analogous to what is done in set -b or set -o notify. When set, it notifies the user immediately of background job completions. When unset, this capability is turned off. The other notification ability comes through the built-in utility notify. The syntax is: notify [%job ... ] By issuing notify with no operands, it causes the C shell to notify the user asynchronously when the state of the current job changes. If given operands, notify asynchronously informs the user of changes in the states of the specified jobs. To add asynchronous notification to the POSIX shell, neither the KornShell extensions to trap, nor the C shell notify environment variable seemed appropriate (notify is not a proper POSIX environment variable name). The set -b option was selected as a compromise. The notify built-in was considered to have more functionality than was required for simple asynchronous notification. Historically, some shells applied the -u option to all parameters including $@ and $*. The standard developers felt that this was a misfeature since it is normal and common for $@ and $* to be used in shell scripts regardless of whether they were passed any arguments. Treating these uses as an error when no arguments are passed reduces the value of -u for its intended purpose of finding spelling mistakes in variable names and uses of unset positional parameters. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.14, Special Built-In Utilities, hash(1p) The Base Definitions volume of POSIX.12017, Section 4.23, Variable Assignment, Section 12.2, Utility Syntax Guidelines COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 SET(1P) Pages that refer to this page: pathchk(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sort(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sort(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON SORT(1) User Commands SORT(1) NAME top sort - sort lines of text files SYNOPSIS top sort [OPTION]... [FILE]... sort [OPTION]... --files0-from=F DESCRIPTION top Write sorted concatenation of all FILE(s) to standard output. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. Ordering options: -b, --ignore-leading-blanks ignore leading blanks -d, --dictionary-order consider only blanks and alphanumeric characters -f, --ignore-case fold lower case to upper case characters -g, --general-numeric-sort compare according to general numerical value -i, --ignore-nonprinting consider only printable characters -M, --month-sort compare (unknown) < 'JAN' < ... < 'DEC' -h, --human-numeric-sort compare human readable numbers (e.g., 2K 1G) -n, --numeric-sort compare according to string numerical value -R, --random-sort shuffle, but group identical keys. See shuf(1) --random-source=FILE get random bytes from FILE -r, --reverse reverse the result of comparisons --sort=WORD sort according to WORD: general-numeric -g, human-numeric -h, month -M, numeric -n, random -R, version -V -V, --version-sort natural sort of (version) numbers within text Other options: --batch-size=NMERGE merge at most NMERGE inputs at once; for more use temp files -c, --check, --check=diagnose-first check for sorted input; do not sort -C, --check=quiet, --check=silent like -c, but do not report first bad line --compress-program=PROG compress temporaries with PROG; decompress them with PROG -d --debug annotate the part of the line used to sort, and warn about questionable usage to stderr --files0-from=F read input from the files specified by NUL-terminated names in file F; If F is - then read names from standard input -k, --key=KEYDEF sort via a key; KEYDEF gives location and type -m, --merge merge already sorted files; do not sort -o, --output=FILE write result to FILE instead of standard output -s, --stable stabilize sort by disabling last-resort comparison -S, --buffer-size=SIZE use SIZE for main memory buffer -t, --field-separator=SEP use SEP instead of non-blank to blank transition -T, --temporary-directory=DIR use DIR for temporaries, not $TMPDIR or /tmp; multiple options specify multiple directories --parallel=N change the number of sorts run concurrently to N -u, --unique with -c, check for strict ordering; without -c, output only the first of an equal run -z, --zero-terminated line delimiter is NUL, not newline --help display this help and exit --version output version information and exit KEYDEF is F[.C][OPTS][,F[.C][OPTS]] for start and stop position, where F is a field number and C a character position in the field; both are origin 1, and the stop position defaults to the line's end. If neither -t nor -b is in effect, characters in a field are counted from the beginning of the preceding whitespace. OPTS is one or more single-letter ordering options [bdfgiMhnRrV], which override global ordering options for that key. If no key is given, use the entire line as the key. Use --debug to diagnose incorrect key usage. SIZE may be followed by the following multiplicative suffixes: % 1% of memory, b 1, K 1024 (default), and so on for M, G, T, P, E, Z, Y, R, Q. *** WARNING *** The locale specified by the environment affects sort order. Set LC_ALL=C to get the traditional sort order that uses native byte values. AUTHOR top Written by Mike Haertel and Paul Eggert. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top shuf(1), uniq(1) Full documentation <https://www.gnu.org/software/coreutils/sort> or available locally via: info '(coreutils) sort invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 SORT(1) Pages that refer to this page: column(1), grep(1), look(1), prlimit(1), ps(1), uniq(1), qsort(3), environ(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. uniq(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training uniq(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON UNIQ(1) User Commands UNIQ(1) NAME top uniq - report or omit repeated lines SYNOPSIS top uniq [OPTION]... [INPUT [OUTPUT]] DESCRIPTION top Filter adjacent matching lines from INPUT (or standard input), writing to OUTPUT (or standard output). With no options, matching lines are merged to the first occurrence. Mandatory arguments to long options are mandatory for short options too. -c, --count prefix lines by the number of occurrences -d, --repeated only print duplicate lines, one for each group -D print all duplicate lines --all-repeated[=METHOD] like -D, but allow separating groups with an empty line; METHOD={none(default),prepend,separate} -f, --skip-fields=N avoid comparing the first N fields --group[=METHOD] show all items, separating groups with an empty line; METHOD={separate(default),prepend,append,both} -i, --ignore-case ignore differences in case when comparing -s, --skip-chars=N avoid comparing the first N characters -u, --unique only print unique lines -z, --zero-terminated line delimiter is NUL, not newline -w, --check-chars=N compare no more than N characters in lines --help display this help and exit --version output version information and exit A field is a run of blanks (usually spaces and/or TABs), then non-blank characters. Fields are skipped before chars. Note: 'uniq' does not detect repeated lines unless they are adjacent. You may want to sort the input first, or use 'sort -u' without 'uniq'. AUTHOR top Written by Richard M. Stallman and David MacKenzie. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top comm(1), join(1), sort(1) Full documentation <https://www.gnu.org/software/coreutils/uniq> or available locally via: info '(coreutils) uniq invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 UNIQ(1) Pages that refer to this page: comm(1), join(1), sort(1) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. comm(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training comm(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON COMM(1) User Commands COMM(1) NAME top comm - compare two sorted files line by line SYNOPSIS top comm [OPTION]... FILE1 FILE2 DESCRIPTION top Compare sorted files FILE1 and FILE2 line by line. When FILE1 or FILE2 (not both) is -, read standard input. With no options, produce three-column output. Column one contains lines unique to FILE1, column two contains lines unique to FILE2, and column three contains lines common to both files. -1 suppress column 1 (lines unique to FILE1) -2 suppress column 2 (lines unique to FILE2) -3 suppress column 3 (lines that appear in both files) --check-order check that the input is correctly sorted, even if all input lines are pairable --nocheck-order do not check that the input is correctly sorted --output-delimiter=STR separate columns with STR --total output a summary -z, --zero-terminated line delimiter is NUL, not newline --help display this help and exit --version output version information and exit Note, comparisons honor the rules specified by 'LC_COLLATE'. EXAMPLES top comm -12 file1 file2 Print only lines present in both file1 and file2. comm -3 file1 file2 Print lines in file1 not in file2, and vice versa. AUTHOR top Written by Richard M. Stallman and David MacKenzie. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top join(1), uniq(1) Full documentation <https://www.gnu.org/software/coreutils/comm> or available locally via: info '(coreutils) comm invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 COMM(1) Pages that refer to this page: join(1), uniq(1) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if the contents of file "subset" is a subset of file "set" Bash Command:<START>comm -23 <(sort subset | uniq) <(sort set | uniq) | head -1<END>

Check if the directory tree whose name is given as variable $somedir contains no regular files

find "$somedir" -type f -exec echo Found unexpected file {} \;

['find', 'file', 'echo']

Output a Bash command to accomplish the following task. Task: Check if the directory tree whose name is given as variable $somedir contains no regular files Bash Command:<START>find "$somedir" -type f -exec echo Found unexpected file {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # file\n\n> Determine file type.\n> More information: <https://manned.org/file>.\n\n- Give a description of the type of the specified file. Works fine for files with no file extension:\n\n`file {{path/to/file}}`\n\n- Look inside a zipped file and determine the file type(s) inside:\n\n`file -z {{foo.zip}}`\n\n- Allow file to work with special or device files:\n\n`file -s {{path/to/file}}`\n\n- Don't stop at first file type match; keep going until the end of the file:\n\n`file -k {{path/to/file}}`\n\n- Determine the MIME encoding type of a file:\n\n`file -i {{path/to/file}}`\n # echo\n\n> Print given arguments.\n> More information: <https://www.gnu.org/software/coreutils/echo>.\n\n- Print a text message. Note: quotes are optional:\n\n`echo "{{Hello World}}"`\n\n- Print a message with environment variables:\n\n`echo "{{My path is $PATH}}"`\n\n- Print a message without the trailing newline:\n\n`echo -n "{{Hello World}}"`\n\n- Append a message to the file:\n\n`echo "{{Hello World}}" >> {{file.txt}}`\n\n- Enable interpretation of backslash escapes (special characters):\n\n`echo -e "{{Column 1\tColumn 2}}"`\n\n- Print the exit status of the last executed command (Note: In Windows Command Prompt and PowerShell the equivalent commands are `echo %errorlevel%` and `$lastexitcode` respectively):\n\n`echo $?`\n Task: Check if the directory tree whose name is given as variable $somedir contains no regular files Bash Command:<START>find "$somedir" -type f -exec echo Found unexpected file {} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. file(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training file(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | FILES | EXIT STATUS | EXAMPLES | SEE ALSO | STANDARDS CONFORMANCE | SECURITY | MAGIC DIRECTORY | HISTORY | LEGAL NOTICE | BUGS | TODO | AVAILABILITY | COLOPHON FILE(1) General Commands Manual FILE(1) NAME top file determine file type SYNOPSIS top [-bcdEhiklLNnprsSvzZ0] [--apple] [--exclude-quiet] [--extension] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile] [-m magicfiles] [-P name=value] file ... -C [-m magicfiles] [--help] DESCRIPTION top This manual page documents version 5.45 of the command. tests each argument in an attempt to classify it. There are three sets of tests, performed in this order: filesystem tests, magic tests, and language tests. The first test that succeeds causes the file type to be printed. The type printed will usually contain one of the words text (the file contains only printing characters and a few common control characters and is probably safe to read on an ASCII terminal), executable (the file contains the result of compiling a program in a form understandable to some UNIX kernel or another), or data meaning anything else (data is usually binary or non- printable). Exceptions are well-known file formats (core files, tar archives) that are known to contain binary data. When modifying magic files or the program itself, make sure to preserve these keywords. Users depend on knowing that all the readable files in a directory have the word text printed. Don't do as Berkeley did and change shell commands text to shell script. The filesystem tests are based on examining the return from a stat(2) system call. The program checks to see if the file is empty, or if it's some sort of special file. Any known file types appropriate to the system you are running on (sockets, symbolic links, or named pipes (FIFOs) on those systems that implement them) are intuited if they are defined in the system header file <sys/stat.h>. The magic tests are used to check for files with data in particular fixed formats. The canonical example of this is a binary executable (compiled program) a.out file, whose format is defined in <elf.h>, <a.out.h> and possibly <exec.h> in the standard include directory. These files have a magic number stored in a particular place near the beginning of the file that tells the UNIX operating system that the file is a binary executable, and which of several types thereof. The concept of a magic number has been applied by extension to data files. Any file with some invariant identifier at a small fixed offset into the file can usually be described in this way. The information identifying these files is read from the compiled magic file /usr/local/share/misc/magic.mgc, or the files in the directory /usr/local/share/misc/magic if the compiled file does not exist. In addition, if $HOME/.magic.mgc or $HOME/.magic exists, it will be used in preference to the system magic files. If a file does not match any of the entries in the magic file, it is examined to see if it seems to be a text file. ASCII, ISO-8859-x, non-ISO 8-bit extended-ASCII character sets (such as those used on Macintosh and IBM PC systems), UTF-8-encoded Unicode, UTF-16-encoded Unicode, and EBCDIC character sets can be distinguished by the different ranges and sequences of bytes that constitute printable text in each set. If a file passes any of these tests, its character set is reported. ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified as text because they will be mostly readable on nearly any terminal; UTF-16 and EBCDIC are only character data because, while they contain text, it is text that will require translation before it can be read. In addition, will attempt to determine other characteristics of text-type files. If the lines of a file are terminated by CR, CRLF, or NEL, instead of the Unix-standard LF, this will be reported. Files that contain embedded escape sequences or overstriking will also be identified. Once has determined the character set used in a text-type file, it will attempt to determine in what language the file is written. The language tests look for particular strings (cf. <names.h>) that can appear anywhere in the first few blocks of a file. For example, the keyword .br indicates that the file is most likely a troff(1) input file, just as the keyword struct indicates a C program. These tests are less reliable than the previous two groups, so they are performed last. The language test routines also test for some miscellany (such as tar(1) archives, JSON files). Any file that cannot be identified as having been written in any of the character sets listed above is simply said to be data. OPTIONS top --apple Causes the command to output the file type and creator code as used by older MacOS versions. The code consists of eight letters, the first describing the file type, the latter the creator. This option works properly only for file formats that have the apple-style output defined. -b, --brief Do not prepend filenames to output lines (brief mode). -C, --compile Write a magic.mgc output file that contains a pre-parsed version of the magic file or directory. -c, --checking-printout Cause a checking printout of the parsed form of the magic file. This is usually used in conjunction with the -m option to debug a new magic file before installing it. -d Prints internal debugging information to stderr. -E On filesystem errors (file not found etc), instead of handling the error as regular output as POSIX mandates and keep going, issue an error message and exit. -e, --exclude testname Exclude the test named in testname from the list of tests made to determine the file type. Valid test names are: apptype EMX application type (only on EMX). ascii Various types of text files (this test will try to guess the text encoding, irrespective of the setting of the encoding option). encoding Different text encodings for soft magic tests. tokens Ignored for backwards compatibility. cdf Prints details of Compound Document Files. compress Checks for, and looks inside, compressed files. csv Checks Comma Separated Value files. elf Prints ELF file details, provided soft magic tests are enabled and the elf magic is found. json Examines JSON (RFC-7159) files by parsing them for compliance. soft Consults magic files. simh Examines SIMH tape files. tar Examines tar files by verifying the checksum of the 512 byte tar header. Excluding this test can provide more detailed content description by using the soft magic method. text A synonym for ascii. --exclude-quiet Like --exclude but ignore tests that does not know about. This is intended for compatibility with older versions of . --extension Print a slash-separated list of valid extensions for the file type found. -F, --separator separator Use the specified string as the separator between the filename and the file result returned. Defaults to :. -f, --files-from namefile Read the names of the files to be examined from namefile (one per line) before the argument list. Either namefile or at least one filename argument must be present; to test the standard input, use - as a filename argument. Please note that namefile is unwrapped and the enclosed filenames are processed when this option is encountered and before any further options processing is done. This allows one to process multiple lists of files with different command line arguments on the same invocation. Thus if you want to set the delimiter, you need to do it before you specify the list of files, like: -F @ -f namefile, instead of: -f namefile -F @. -h, --no-dereference This option causes symlinks not to be followed (on systems that support symbolic links). This is the default if the environment variable POSIXLY_CORRECT is not defined. -i, --mime Causes the command to output mime type strings rather than the more traditional human readable ones. Thus it may say text/plain; charset=us-ascii rather than ASCII text. --mime-type, --mime-encoding Like -i, but print only the specified element(s). -k, --keep-going Don't stop at the first match, keep going. Subsequent matches will be have the string \012- prepended. (If you want a newline, see the -r option.) The magic pattern with the highest strength (see the -l option) comes first. -l, --list Shows a list of patterns and their strength sorted descending by magic(4) strength which is used for the matching (see also the -k option). -L, --dereference This option causes symlinks to be followed, as the like- named option in ls(1) (on systems that support symbolic links). This is the default if the environment variable POSIXLY_CORRECT is defined. -m, --magic-file magicfiles Specify an alternate list of files and directories containing magic. This can be a single item, or a colon- separated list. If a compiled magic file is found alongside a file or directory, it will be used instead. -N, --no-pad Don't pad filenames so that they align in the output. -n, --no-buffer Force stdout to be flushed after checking each file. This is only useful if checking a list of files. It is intended to be used by programs that want filetype output from a pipe. -p, --preserve-date On systems that support utime(3) or utimes(2), attempt to preserve the access time of files analyzed, to pretend that never read them. -P, --parameter name=value Set various parameter limits. Name Default Explanation bytes 1M max number of bytes to read from file elf_notes 256 max ELF notes processed elf_phnum 2K max ELF program sections processed elf_shnum 32K max ELF sections processed elf_shsize 128MB max ELF section size processed encoding 65K max number of bytes to determine encoding indir 50 recursion limit for indirect magic name 50 use count limit for name/use magic regex 8K length limit for regex searches -r, --raw Don't translate unprintable characters to \ooo. Normally translates unprintable characters to their octal representation. -s, --special-files Normally, only attempts to read and determine the type of argument files which stat(2) reports are ordinary files. This prevents problems, because reading special files may have peculiar consequences. Specifying the -s option causes to also read argument files which are block or character special files. This is useful for determining the filesystem types of the data in raw disk partitions, which are block special files. This option also causes to disregard the file size as reported by stat(2) since on some systems it reports a zero size for raw disk partitions. -S, --no-sandbox On systems where libseccomp (https://github.com/seccomp/libseccomp ) is available, the -S option disables sandboxing which is enabled by default. This option is needed for to execute external decompressing programs, i.e. when the -z option is specified and the built-in decompressors are not available. On systems where sandboxing is not available, this option has no effect. -v, --version Print the version of the program and exit. -z, --uncompress Try to look inside compressed files. -Z, --uncompress-noreport Try to look inside compressed files, but report information about the contents only not the compression. -0, --print0 Output a null character \0 after the end of the filename. Nice to cut(1) the output. This does not affect the separator, which is still printed. If this option is repeated more than once, then prints just the filename followed by a NUL followed by the description (or ERROR: text) followed by a second NUL for each entry. --help Print a help message and exit. ENVIRONMENT top The environment variable MAGIC can be used to set the default magic file name. If that variable is set, then will not attempt to open $HOME/.magic. adds .mgc to the value of this variable as appropriate. The environment variable POSIXLY_CORRECT controls (on systems that support symbolic links), whether will attempt to follow symlinks or not. If set, then follows symlink, otherwise it does not. This is also controlled by the -L and -h options. FILES top /usr/local/share/misc/magic.mgc Default compiled list of magic. /usr/local/share/misc/magic Directory containing default magic files. EXIT STATUS top will exit with 0 if the operation was successful or >0 if an error was encountered. The following errors cause diagnostic messages, but don't affect the program exit code (as POSIX requires), unless -E is specified: A file cannot be found There is no permission to read a file The file type cannot be determined EXAMPLES top $ file file.c file /dev/{wd0a,hda} file.c: C program text file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), stripped /dev/wd0a: block special (0/0) /dev/hda: block special (3/0) $ file -s /dev/wd0{b,d} /dev/wd0b: data /dev/wd0d: x86 boot sector $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} /dev/hda: x86 boot sector /dev/hda1: Linux/i386 ext2 filesystem /dev/hda2: x86 boot sector /dev/hda3: x86 boot sector, extended partition table /dev/hda4: Linux/i386 ext2 filesystem /dev/hda5: Linux/i386 swap file /dev/hda6: Linux/i386 swap file /dev/hda7: Linux/i386 swap file /dev/hda8: Linux/i386 swap file /dev/hda9: empty /dev/hda10: empty $ file -i file.c file /dev/{wd0a,hda} file.c: text/x-c file: application/x-executable /dev/hda: application/x-not-regular-file /dev/wd0a: application/x-not-regular-file SEE ALSO top hexdump(1), od(1), strings(1), magic(4) STANDARDS CONFORMANCE top This program is believed to exceed the System V Interface Definition of FILE(CMD), as near as one can determine from the vague language contained therein. Its behavior is mostly compatible with the System V program of the same name. This version knows more magic, however, so it will produce different (albeit more accurate) output in many cases. The one significant difference between this version and System V is that this version treats any white space as a delimiter, so that spaces in pattern strings must be escaped. For example, >10 string language impress (imPRESS data) in an existing magic file would have to be changed to >10 string language\ impress (imPRESS data) In addition, in this version, if a pattern string contains a backslash, it must be escaped. For example 0 string \begindata Andrew Toolkit document in an existing magic file would have to be changed to 0 string \\begindata Andrew Toolkit document SunOS releases 3.2 and later from Sun Microsystems include a command derived from the System V one, but with some extensions. This version differs from Sun's only in minor ways. It includes the extension of the & operator, used as, for example, >16 long&0x7fffffff >0 not stripped SECURITY top On systems where libseccomp (https://github.com/seccomp/libseccomp ) is available, is enforces limiting system calls to only the ones necessary for the operation of the program. This enforcement does not provide any security benefit when is asked to decompress input files running external programs with the -z option. To enable execution of external decompressors, one needs to disable sandboxing using the -S option. MAGIC DIRECTORY top The magic file entries have been collected from various sources, mainly USENET, and contributed by various authors. Christos Zoulas (address below) will collect additional or corrected magic file entries. A consolidation of magic file entries will be distributed periodically. The order of entries in the magic file is significant. Depending on what system you are using, the order that they are put together may be incorrect. If your old command uses a magic file, keep the old magic file around for comparison purposes (rename it to /usr/local/share/misc/magic.orig). HISTORY top There has been a command in every UNIX since at least Research Version 4 (man page dated November, 1973). The System V version introduced one significant major change: the external list of magic types. This slowed the program down slightly but made it a lot more flexible. This program, based on the System V version, was written by Ian Darwin ian@darwinsys.com without looking at anybody else's source code. John Gilmore revised the code extensively, making it better than the first version. Geoff Collyer found several inadequacies and provided some magic file entries. Contributions of the & operator by Rob McMahon, cudcv@warwick.ac.uk, 1989. Guy Harris, guy@netapp.com, made many changes from 1993 to the present. Primary development and maintenance from 1990 to the present by Christos Zoulas christos@astron.com. Altered by Chris Lowth chris@lowth.com, 2000: handle the -i option to output mime type strings, using an alternative magic file and internal logic. Altered by Eric Fischer enf@pobox.com, July, 2000, to identify character codes and attempt to identify the languages of non- ASCII files. Altered by Reuben Thomas rrt@sc3d.org, 2007-2011, to improve MIME support, merge MIME and non-MIME magic, support directories as well as files of magic, apply many bug fixes, update and fix a lot of magic, improve the build system, improve the documentation, and rewrite the Python bindings in pure Python. The list of contributors to the magic directory (magic files) is too long to include here. You know who you are; thank you. Many contributors are listed in the source files. LEGAL NOTICE top Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. Covered by the standard Berkeley Software Distribution copyright; see the file COPYING in the source distribution. The files tar.h and is_tar.c were written by John Gilmore from his public-domain tar(1) program, and are not covered by the above license. BUGS top Please report bugs and send patches to the bug tracker at https://bugs.astron.com/ or the mailing list at file@astron.com (visit https://mailman.astron.com/mailman/listinfo/file first to subscribe). TODO top Fix output so that tests for MIME and APPLE flags are not needed all over the place, and actual output is only done in one place. This needs a design. Suggestion: push possible outputs on to a list, then pick the last-pushed (most specific, one hopes) value at the end, or use a default if the list is empty. This should not slow down evaluation. The handling of MAGIC_CONTINUE and printing \012- between entries is clumsy and complicated; refactor and centralize. Some of the encoding logic is hard-coded in encoding.c and can be moved to the magic files if we had a !:charset annotation. Continue to squash all magic bugs. See Debian BTS for a good source. Store arbitrarily long strings, for example for %s patterns, so that they can be printed out. Fixes Debian bug #271672. This can be done by allocating strings in a string pool, storing the string pool at the end of the magic file and converting all the string pointers to relative offsets from the string pool. Add syntax for relative offsets after current level (Debian bug #466037). Make file -ki work, i.e. give multiple MIME types. Add a zip library so we can peek inside Office2007 documents to print more details about their contents. Add an option to print URLs for the sources of the file descriptions. Combine script searches and add a way to map executable names to MIME types (e.g. have a magic value for !:mime which causes the resulting string to be looked up in a table). This would avoid adding the same magic repeatedly for each new hash-bang interpreter. When a file descriptor is available, we can skip and adjust the buffer instead of the hacky buffer management we do now. Fix name and use to check for consistency at compile time (duplicate name, use pointing to undefined name ). Make name / use more efficient by keeping a sorted list of names. Special-case ^ to flip endianness in the parser so that it does not have to be escaped, and document it. If the offsets specified internally in the file exceed the buffer size ( HOWMANY variable in file.h), then we don't seek to that offset, but we give up. It would be better if buffer managements was done when the file descriptor is available so we can seek around the file. One must be careful though because this has performance and thus security considerations, because one can slow down things by repeatedly seeking. There is support now for keeping separate buffers and having offsets from the end of the file, but the internal buffer management still needs an overhaul. AVAILABILITY top You can obtain the original author's latest version by anonymous FTP on ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz. COLOPHON top This page is part of the file (a file type guesser) project. Information about the project can be found at http://www.darwinsys.com/file/. If you have a bug report for this manual page, see http://bugs.gw.com/my_view_page.php. This page was obtained from the project's upstream Git read-only mirror of the CVS repository https://github.com/glensc/file on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU May 21, 2023 FILE(1) Pages that refer to this page: dh_installmanpages(1), dh_strip(1), ippeveprinter(1), pmcd(1), scr_dump(5), term(5), suffixes(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. echo(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training echo(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON ECHO(1) User Commands ECHO(1) NAME top echo - display a line of text SYNOPSIS top echo [SHORT-OPTION]... [STRING]... echo LONG-OPTION DESCRIPTION top Echo the STRING(s) to standard output. -n do not output the trailing newline -e enable interpretation of backslash escapes -E disable interpretation of backslash escapes (default) --help display this help and exit --version output version information and exit If -e is in effect, the following sequences are recognized: \\ backslash \a alert (BEL) \b backspace \c produce no further output \e escape \f form feed \n new line \r carriage return \t horizontal tab \v vertical tab \0NNN byte with octal value NNN (1 to 3 digits) \xHH byte with hexadecimal value HH (1 to 2 digits) NOTE: your shell may have its own version of echo, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports. NOTE: printf(1) is a preferred alternative, which does not have issues outputting option-like strings. AUTHOR top Written by Brian Fox and Chet Ramey. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top printf(1) Full documentation <https://www.gnu.org/software/coreutils/echo> or available locally via: info '(coreutils) echo invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 ECHO(1) Pages that refer to this page: ldapcompare(1), systemd-ask-password(1), systemd-run(1), cpuset(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if the directory tree whose name is given as variable $somedir contains no regular files Bash Command:<START>find "$somedir" -type f -exec echo Found unexpected file {} \;<END>

Check if the file "somelink" links to exists

ls `readlink somelink`

['ls', 'readlink']

Output a Bash command to accomplish the following task. Task: Check if the file "somelink" links to exists Bash Command:<START>ls `readlink somelink`<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # ls\n\n> List directory contents.\n> More information: <https://www.gnu.org/software/coreutils/ls>.\n\n- List files one per line:\n\n`ls -1`\n\n- List all files, including hidden files:\n\n`ls -a`\n\n- List all files, with trailing `/` added to directory names:\n\n`ls -F`\n\n- Long format list (permissions, ownership, size, and modification date) of all files:\n\n`ls -la`\n\n- Long format list with size displayed using human-readable units (KiB, MiB, GiB):\n\n`ls -lh`\n\n- Long format list sorted by size (descending) recursively:\n\n`ls -lSR`\n\n- Long format list of all files, sorted by modification date (oldest first):\n\n`ls -ltr`\n\n- Only list directories:\n\n`ls -d */`\n # readlink\n\n> Follow symlinks and get symlink information.\n> More information: <https://www.gnu.org/software/coreutils/readlink>.\n\n- Get the actual file to which the symlink points:\n\n`readlink {{path/to/file}}`\n\n- Get the absolute path to a file:\n\n`readlink -f {{path/to/file}}`\n Task: Check if the file "somelink" links to exists Bash Command:<START>ls `readlink somelink`<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: ls(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training ls(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON LS(1) User Commands LS(1) NAME top ls - list directory contents SYNOPSIS top ls [OPTION]... [FILE]... DESCRIPTION top List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort is specified. Mandatory arguments to long options are mandatory for short options too. -a, --all do not ignore entries starting with . -A, --almost-all do not list implied . and .. --author with -l, print the author of each file -b, --escape print C-style escapes for nongraphic characters --block-size=SIZE with -l, scale sizes by SIZE when printing them; e.g., '--block-size=M'; see SIZE format below -B, --ignore-backups do not list implied entries ending with ~ -c with -lt: sort by, and show, ctime (time of last change of file status information); with -l: show ctime and sort by name; otherwise: sort by ctime, newest first -C list entries by columns --color[=WHEN] color the output WHEN; more info below -d, --directory list directories themselves, not their contents -D, --dired generate output designed for Emacs' dired mode -f list all entries in directory order -F, --classify[=WHEN] append indicator (one of */=>@|) to entries WHEN --file-type likewise, except do not append '*' --format=WORD across -x, commas -m, horizontal -x, long -l, single-column -1, verbose -l, vertical -C --full-time like -l --time-style=full-iso -g like -l, but do not list owner --group-directories-first group directories before files; can be augmented with a --sort option, but any use of --sort=none (-U) disables grouping -G, --no-group in a long listing, don't print group names -h, --human-readable with -l and -s, print sizes like 1K 234M 2G etc. --si likewise, but use powers of 1000 not 1024 -H, --dereference-command-line follow symbolic links listed on the command line --dereference-command-line-symlink-to-dir follow each command line symbolic link that points to a directory --hide=PATTERN do not list implied entries matching shell PATTERN (overridden by -a or -A) --hyperlink[=WHEN] hyperlink file names WHEN --indicator-style=WORD append indicator with style WORD to entry names: none (default), slash (-p), file-type (--file-type), classify (-F) -i, --inode print the index number of each file -I, --ignore=PATTERN do not list implied entries matching shell PATTERN -k, --kibibytes default to 1024-byte blocks for file system usage; used only with -s and per directory totals -l use a long listing format -L, --dereference when showing file information for a symbolic link, show information for the file the link references rather than for the link itself -m fill width with a comma separated list of entries -n, --numeric-uid-gid like -l, but list numeric user and group IDs -N, --literal print entry names without quoting -o like -l, but do not list group information -p, --indicator-style=slash append / indicator to directories -q, --hide-control-chars print ? instead of nongraphic characters --show-control-chars show nongraphic characters as-is (the default, unless program is 'ls' and output is a terminal) -Q, --quote-name enclose entry names in double quotes --quoting-style=WORD use quoting style WORD for entry names: literal, locale, shell, shell-always, shell-escape, shell-escape-always, c, escape (overrides QUOTING_STYLE environment variable) -r, --reverse reverse order while sorting -R, --recursive list subdirectories recursively -s, --size print the allocated size of each file, in blocks -S sort by file size, largest first --sort=WORD sort by WORD instead of name: none (-U), size (-S), time (-t), version (-v), extension (-X), width --time=WORD select which timestamp used to display or sort; access time (-u): atime, access, use; metadata change time (-c): ctime, status; modified time (default): mtime, modification; birth time: birth, creation; with -l, WORD determines which time to show; with --sort=time, sort by WORD (newest first) --time-style=TIME_STYLE time/date format with -l; see TIME_STYLE below -t sort by time, newest first; see --time -T, --tabsize=COLS assume tab stops at each COLS instead of 8 -u with -lt: sort by, and show, access time; with -l: show access time and sort by name; otherwise: sort by access time, newest first -U do not sort; list entries in directory order -v natural sort of (version) numbers within text -w, --width=COLS set output width to COLS. 0 means no limit -x list entries by lines instead of by columns -X sort alphabetically by entry extension -Z, --context print any security context of each file --zero end each output line with NUL, not newline -1 list one file per line --help display this help and exit --version output version information and exit The SIZE argument is an integer and optional unit (example: 10K is 10*1024). Units are K,M,G,T,P,E,Z,Y,R,Q (powers of 1024) or KB,MB,... (powers of 1000). Binary prefixes can be used, too: KiB=K, MiB=M, and so on. The TIME_STYLE argument can be full-iso, long-iso, iso, locale, or +FORMAT. FORMAT is interpreted like in date(1). If FORMAT is FORMAT1<newline>FORMAT2, then FORMAT1 applies to non-recent files and FORMAT2 to recent files. TIME_STYLE prefixed with 'posix-' takes effect only outside the POSIX locale. Also the TIME_STYLE environment variable sets the default style to use. The WHEN argument defaults to 'always' and can also be 'auto' or 'never'. Using color to distinguish file types is disabled both by default and with --color=never. With --color=auto, ls emits color codes only when standard output is connected to a terminal. The LS_COLORS environment variable can change the settings. Use the dircolors(1) command to set it. Exit status: 0 if OK, 1 if minor problems (e.g., cannot access subdirectory), 2 if serious trouble (e.g., cannot access command-line argument). AUTHOR top Written by Richard M. Stallman and David MacKenzie. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top dircolors(1) Full documentation <https://www.gnu.org/software/coreutils/ls> or available locally via: info '(coreutils) ls invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 LS(1) Pages that refer to this page: column(1), find(1), namei(1), stat(2), statx(2), glob(3), strverscmp(3), core(5), dir_colors(5), passwd(5), proc(5), mq_overview(7), symlink(7), lsblk(8), lsof(8), setfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. readlink(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training readlink(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON READLINK(1) User Commands READLINK(1) NAME top readlink - print resolved symbolic links or canonical file names SYNOPSIS top readlink [OPTION]... FILE... DESCRIPTION top Note realpath(1) is the preferred command to use for canonicalization functionality. Print value of a symbolic link or canonical file name -f, --canonicalize canonicalize by following every symlink in every component of the given name recursively; all but the last component must exist -e, --canonicalize-existing canonicalize by following every symlink in every component of the given name recursively, all components must exist -m, --canonicalize-missing canonicalize by following every symlink in every component of the given name recursively, without requirements on components existence -n, --no-newline do not output the trailing delimiter -q, --quiet -s, --silent suppress most error messages (on by default) -v, --verbose report error messages -z, --zero end each output line with NUL, not newline --help display this help and exit --version output version information and exit AUTHOR top Written by Dmitry V. Levin. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top readlink(2), realpath(1), realpath(3) Full documentation <https://www.gnu.org/software/coreutils/readlink> or available locally via: info '(coreutils) readlink invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 READLINK(1) Pages that refer to this page: basename(1), dirname(1), dpkg-realpath(1), realpath(1), unshare(1), mount(2), readlink(2), unshare(2), namespaces(7), mount(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check if the file "somelink" links to exists Bash Command:<START>ls `readlink somelink`<END>

Check md5sum of directory /path against the checksum saved in file 'file'

du -csxb /path | md5sum -c file

['md5sum', 'du', 'file']

Output a Bash command to accomplish the following task. Task: Check md5sum of directory /path against the checksum saved in file 'file' Bash Command:<START>du -csxb /path | md5sum -c file<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # md5sum\n\n> Calculate MD5 cryptographic checksums.\n> More information: <https://www.gnu.org/software/coreutils/md5sum>.\n\n- Calculate the MD5 checksum for one or more files:\n\n`md5sum {{path/to/file1 path/to/file2 ...}}`\n\n- Calculate and save the list of MD5 checksums to a file:\n\n`md5sum {{path/to/file1 path/to/file2 ...}} > {{path/to/file.md5}}`\n\n- Calculate an MD5 checksum from `stdin`:\n\n`{{command}} | md5sum`\n\n- Read a file of MD5 sums and filenames and verify all files have matching checksums:\n\n`md5sum --check {{path/to/file.md5}}`\n\n- Only show a message for missing files or when verification fails:\n\n`md5sum --check --quiet {{path/to/file.md5}}`\n\n- Only show a message when verification fails, ignoring missing files:\n\n`md5sum --ignore-missing --check --quiet {{path/to/file.md5}}`\n # du\n\n> Disk usage: estimate and summarize file and directory space usage.\n> More information: <https://www.gnu.org/software/coreutils/du>.\n\n- List the sizes of a directory and any subdirectories, in the given unit (B/KiB/MiB):\n\n`du -{{b|k|m}} {{path/to/directory}}`\n\n- List the sizes of a directory and any subdirectories, in human-readable form (i.e. auto-selecting the appropriate unit for each size):\n\n`du -h {{path/to/directory}}`\n\n- Show the size of a single directory, in human-readable units:\n\n`du -sh {{path/to/directory}}`\n\n- List the human-readable sizes of a directory and of all the files and directories within it:\n\n`du -ah {{path/to/directory}}`\n\n- List the human-readable sizes of a directory and any subdirectories, up to N levels deep:\n\n`du -h --max-depth=N {{path/to/directory}}`\n\n- List the human-readable size of all `.jpg` files in subdirectories of the current directory, and show a cumulative total at the end:\n\n`du -ch {{*/*.jpg}}`\n # file\n\n> Determine file type.\n> More information: <https://manned.org/file>.\n\n- Give a description of the type of the specified file. Works fine for files with no file extension:\n\n`file {{path/to/file}}`\n\n- Look inside a zipped file and determine the file type(s) inside:\n\n`file -z {{foo.zip}}`\n\n- Allow file to work with special or device files:\n\n`file -s {{path/to/file}}`\n\n- Don't stop at first file type match; keep going until the end of the file:\n\n`file -k {{path/to/file}}`\n\n- Determine the MIME encoding type of a file:\n\n`file -i {{path/to/file}}`\n Task: Check md5sum of directory /path against the checksum saved in file 'file' Bash Command:<START>du -csxb /path | md5sum -c file<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: md5sum(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training md5sum(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | BUGS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON MD5SUM(1) User Commands MD5SUM(1) NAME top md5sum - compute and check MD5 message digest SYNOPSIS top md5sum [OPTION]... [FILE]... DESCRIPTION top Print or check MD5 (128-bit) checksums. With no FILE, or when FILE is -, read standard input. -b, --binary read in binary mode -c, --check read checksums from the FILEs and check them --tag create a BSD-style checksum -t, --text read in text mode (default) -z, --zero end each output line with NUL, not newline, and disable file name escaping The following five options are useful only when verifying checksums: --ignore-missing don't fail or report status for missing files --quiet don't print OK for each successfully verified file --status don't output anything, status code shows success --strict exit non-zero for improperly formatted checksum lines -w, --warn warn about improperly formatted checksum lines --help display this help and exit --version output version information and exit The sums are computed as described in RFC 1321. When checking, the input should be a former output of this program. The default mode is to print a line with: checksum, a space, a character indicating input mode ('*' for binary, ' ' for text or where binary is insignificant), and name for each FILE. Note: There is no difference between binary mode and text mode on GNU systems. BUGS top Do not use the MD5 algorithm for security related purposes. Instead, use an SHA-2 algorithm, implemented in the programs sha224sum(1), sha256sum(1), sha384sum(1), sha512sum(1), or the BLAKE2 algorithm, implemented in b2sum(1) AUTHOR top Written by Ulrich Drepper, Scott Miller, and David Madore. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top cksum(1) Full documentation <https://www.gnu.org/software/coreutils/md5sum> or available locally via: info '(coreutils) md5sum invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 MD5SUM(1) Pages that refer to this page: mcookie(1), pmlogmv(1), deb-md5sums(5), prelink(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. du(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training du(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | PATTERNS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DU(1) User Commands DU(1) NAME top du - estimate file space usage SYNOPSIS top du [OPTION]... [FILE]... du [OPTION]... --files0-from=F DESCRIPTION top Summarize device usage of the set of FILEs, recursively for directories. Mandatory arguments to long options are mandatory for short options too. -0, --null end each output line with NUL, not newline -a, --all write counts for all files, not just directories --apparent-size print apparent sizes rather than device usage; although the apparent size is usually smaller, it may be larger due to holes in ('sparse') files, internal fragmentation, indirect blocks, and the like -B, --block-size=SIZE scale sizes by SIZE before printing them; e.g., '-BM' prints sizes in units of 1,048,576 bytes; see SIZE format below -b, --bytes equivalent to '--apparent-size --block-size=1' -c, --total produce a grand total -D, --dereference-args dereference only symlinks that are listed on the command line -d, --max-depth=N print the total for a directory (or file, with --all) only if it is N or fewer levels below the command line argument; --max-depth=0 is the same as --summarize --files0-from=F summarize device usage of the NUL-terminated file names specified in file F; if F is -, then read names from standard input -H equivalent to --dereference-args (-D) -h, --human-readable print sizes in human readable format (e.g., 1K 234M 2G) --inodes list inode usage information instead of block usage -k like --block-size=1K -L, --dereference dereference all symbolic links -l, --count-links count sizes many times if hard linked -m like --block-size=1M -P, --no-dereference don't follow any symbolic links (this is the default) -S, --separate-dirs for directories do not include size of subdirectories --si like -h, but use powers of 1000 not 1024 -s, --summarize display only a total for each argument -t, --threshold=SIZE exclude entries smaller than SIZE if positive, or entries greater than SIZE if negative --time show time of the last modification of any file in the directory, or any of its subdirectories --time=WORD show time as WORD instead of modification time: atime, access, use, ctime or status --time-style=STYLE show times using STYLE, which can be: full-iso, long-iso, iso, or +FORMAT; FORMAT is interpreted like in 'date' -X, --exclude-from=FILE exclude files that match any pattern in FILE --exclude=PATTERN exclude files that match PATTERN -x, --one-file-system skip directories on different file systems --help display this help and exit --version output version information and exit Display values are in units of the first available SIZE from --block-size, and the DU_BLOCK_SIZE, BLOCK_SIZE and BLOCKSIZE environment variables. Otherwise, units default to 1024 bytes (or 512 if POSIXLY_CORRECT is set). The SIZE argument is an integer and optional unit (example: 10K is 10*1024). Units are K,M,G,T,P,E,Z,Y,R,Q (powers of 1024) or KB,MB,... (powers of 1000). Binary prefixes can be used, too: KiB=K, MiB=M, and so on. PATTERNS top PATTERN is a shell pattern (not a regular expression). The pattern ? matches any one character, whereas * matches any string (composed of zero, one or multiple characters). For example, *.o will match any files whose names end in .o. Therefore, the command du --exclude='*.o' will skip all files and subdirectories ending in .o (including the file .o itself). AUTHOR top Written by Torbjorn Granlund, David MacKenzie, Paul Eggert, and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top Full documentation <https://www.gnu.org/software/coreutils/du> or available locally via: info '(coreutils) du invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DU(1) Pages that refer to this page: tmpfs(5), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. file(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training file(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | FILES | EXIT STATUS | EXAMPLES | SEE ALSO | STANDARDS CONFORMANCE | SECURITY | MAGIC DIRECTORY | HISTORY | LEGAL NOTICE | BUGS | TODO | AVAILABILITY | COLOPHON FILE(1) General Commands Manual FILE(1) NAME top file determine file type SYNOPSIS top [-bcdEhiklLNnprsSvzZ0] [--apple] [--exclude-quiet] [--extension] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile] [-m magicfiles] [-P name=value] file ... -C [-m magicfiles] [--help] DESCRIPTION top This manual page documents version 5.45 of the command. tests each argument in an attempt to classify it. There are three sets of tests, performed in this order: filesystem tests, magic tests, and language tests. The first test that succeeds causes the file type to be printed. The type printed will usually contain one of the words text (the file contains only printing characters and a few common control characters and is probably safe to read on an ASCII terminal), executable (the file contains the result of compiling a program in a form understandable to some UNIX kernel or another), or data meaning anything else (data is usually binary or non- printable). Exceptions are well-known file formats (core files, tar archives) that are known to contain binary data. When modifying magic files or the program itself, make sure to preserve these keywords. Users depend on knowing that all the readable files in a directory have the word text printed. Don't do as Berkeley did and change shell commands text to shell script. The filesystem tests are based on examining the return from a stat(2) system call. The program checks to see if the file is empty, or if it's some sort of special file. Any known file types appropriate to the system you are running on (sockets, symbolic links, or named pipes (FIFOs) on those systems that implement them) are intuited if they are defined in the system header file <sys/stat.h>. The magic tests are used to check for files with data in particular fixed formats. The canonical example of this is a binary executable (compiled program) a.out file, whose format is defined in <elf.h>, <a.out.h> and possibly <exec.h> in the standard include directory. These files have a magic number stored in a particular place near the beginning of the file that tells the UNIX operating system that the file is a binary executable, and which of several types thereof. The concept of a magic number has been applied by extension to data files. Any file with some invariant identifier at a small fixed offset into the file can usually be described in this way. The information identifying these files is read from the compiled magic file /usr/local/share/misc/magic.mgc, or the files in the directory /usr/local/share/misc/magic if the compiled file does not exist. In addition, if $HOME/.magic.mgc or $HOME/.magic exists, it will be used in preference to the system magic files. If a file does not match any of the entries in the magic file, it is examined to see if it seems to be a text file. ASCII, ISO-8859-x, non-ISO 8-bit extended-ASCII character sets (such as those used on Macintosh and IBM PC systems), UTF-8-encoded Unicode, UTF-16-encoded Unicode, and EBCDIC character sets can be distinguished by the different ranges and sequences of bytes that constitute printable text in each set. If a file passes any of these tests, its character set is reported. ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified as text because they will be mostly readable on nearly any terminal; UTF-16 and EBCDIC are only character data because, while they contain text, it is text that will require translation before it can be read. In addition, will attempt to determine other characteristics of text-type files. If the lines of a file are terminated by CR, CRLF, or NEL, instead of the Unix-standard LF, this will be reported. Files that contain embedded escape sequences or overstriking will also be identified. Once has determined the character set used in a text-type file, it will attempt to determine in what language the file is written. The language tests look for particular strings (cf. <names.h>) that can appear anywhere in the first few blocks of a file. For example, the keyword .br indicates that the file is most likely a troff(1) input file, just as the keyword struct indicates a C program. These tests are less reliable than the previous two groups, so they are performed last. The language test routines also test for some miscellany (such as tar(1) archives, JSON files). Any file that cannot be identified as having been written in any of the character sets listed above is simply said to be data. OPTIONS top --apple Causes the command to output the file type and creator code as used by older MacOS versions. The code consists of eight letters, the first describing the file type, the latter the creator. This option works properly only for file formats that have the apple-style output defined. -b, --brief Do not prepend filenames to output lines (brief mode). -C, --compile Write a magic.mgc output file that contains a pre-parsed version of the magic file or directory. -c, --checking-printout Cause a checking printout of the parsed form of the magic file. This is usually used in conjunction with the -m option to debug a new magic file before installing it. -d Prints internal debugging information to stderr. -E On filesystem errors (file not found etc), instead of handling the error as regular output as POSIX mandates and keep going, issue an error message and exit. -e, --exclude testname Exclude the test named in testname from the list of tests made to determine the file type. Valid test names are: apptype EMX application type (only on EMX). ascii Various types of text files (this test will try to guess the text encoding, irrespective of the setting of the encoding option). encoding Different text encodings for soft magic tests. tokens Ignored for backwards compatibility. cdf Prints details of Compound Document Files. compress Checks for, and looks inside, compressed files. csv Checks Comma Separated Value files. elf Prints ELF file details, provided soft magic tests are enabled and the elf magic is found. json Examines JSON (RFC-7159) files by parsing them for compliance. soft Consults magic files. simh Examines SIMH tape files. tar Examines tar files by verifying the checksum of the 512 byte tar header. Excluding this test can provide more detailed content description by using the soft magic method. text A synonym for ascii. --exclude-quiet Like --exclude but ignore tests that does not know about. This is intended for compatibility with older versions of . --extension Print a slash-separated list of valid extensions for the file type found. -F, --separator separator Use the specified string as the separator between the filename and the file result returned. Defaults to :. -f, --files-from namefile Read the names of the files to be examined from namefile (one per line) before the argument list. Either namefile or at least one filename argument must be present; to test the standard input, use - as a filename argument. Please note that namefile is unwrapped and the enclosed filenames are processed when this option is encountered and before any further options processing is done. This allows one to process multiple lists of files with different command line arguments on the same invocation. Thus if you want to set the delimiter, you need to do it before you specify the list of files, like: -F @ -f namefile, instead of: -f namefile -F @. -h, --no-dereference This option causes symlinks not to be followed (on systems that support symbolic links). This is the default if the environment variable POSIXLY_CORRECT is not defined. -i, --mime Causes the command to output mime type strings rather than the more traditional human readable ones. Thus it may say text/plain; charset=us-ascii rather than ASCII text. --mime-type, --mime-encoding Like -i, but print only the specified element(s). -k, --keep-going Don't stop at the first match, keep going. Subsequent matches will be have the string \012- prepended. (If you want a newline, see the -r option.) The magic pattern with the highest strength (see the -l option) comes first. -l, --list Shows a list of patterns and their strength sorted descending by magic(4) strength which is used for the matching (see also the -k option). -L, --dereference This option causes symlinks to be followed, as the like- named option in ls(1) (on systems that support symbolic links). This is the default if the environment variable POSIXLY_CORRECT is defined. -m, --magic-file magicfiles Specify an alternate list of files and directories containing magic. This can be a single item, or a colon- separated list. If a compiled magic file is found alongside a file or directory, it will be used instead. -N, --no-pad Don't pad filenames so that they align in the output. -n, --no-buffer Force stdout to be flushed after checking each file. This is only useful if checking a list of files. It is intended to be used by programs that want filetype output from a pipe. -p, --preserve-date On systems that support utime(3) or utimes(2), attempt to preserve the access time of files analyzed, to pretend that never read them. -P, --parameter name=value Set various parameter limits. Name Default Explanation bytes 1M max number of bytes to read from file elf_notes 256 max ELF notes processed elf_phnum 2K max ELF program sections processed elf_shnum 32K max ELF sections processed elf_shsize 128MB max ELF section size processed encoding 65K max number of bytes to determine encoding indir 50 recursion limit for indirect magic name 50 use count limit for name/use magic regex 8K length limit for regex searches -r, --raw Don't translate unprintable characters to \ooo. Normally translates unprintable characters to their octal representation. -s, --special-files Normally, only attempts to read and determine the type of argument files which stat(2) reports are ordinary files. This prevents problems, because reading special files may have peculiar consequences. Specifying the -s option causes to also read argument files which are block or character special files. This is useful for determining the filesystem types of the data in raw disk partitions, which are block special files. This option also causes to disregard the file size as reported by stat(2) since on some systems it reports a zero size for raw disk partitions. -S, --no-sandbox On systems where libseccomp (https://github.com/seccomp/libseccomp ) is available, the -S option disables sandboxing which is enabled by default. This option is needed for to execute external decompressing programs, i.e. when the -z option is specified and the built-in decompressors are not available. On systems where sandboxing is not available, this option has no effect. -v, --version Print the version of the program and exit. -z, --uncompress Try to look inside compressed files. -Z, --uncompress-noreport Try to look inside compressed files, but report information about the contents only not the compression. -0, --print0 Output a null character \0 after the end of the filename. Nice to cut(1) the output. This does not affect the separator, which is still printed. If this option is repeated more than once, then prints just the filename followed by a NUL followed by the description (or ERROR: text) followed by a second NUL for each entry. --help Print a help message and exit. ENVIRONMENT top The environment variable MAGIC can be used to set the default magic file name. If that variable is set, then will not attempt to open $HOME/.magic. adds .mgc to the value of this variable as appropriate. The environment variable POSIXLY_CORRECT controls (on systems that support symbolic links), whether will attempt to follow symlinks or not. If set, then follows symlink, otherwise it does not. This is also controlled by the -L and -h options. FILES top /usr/local/share/misc/magic.mgc Default compiled list of magic. /usr/local/share/misc/magic Directory containing default magic files. EXIT STATUS top will exit with 0 if the operation was successful or >0 if an error was encountered. The following errors cause diagnostic messages, but don't affect the program exit code (as POSIX requires), unless -E is specified: A file cannot be found There is no permission to read a file The file type cannot be determined EXAMPLES top $ file file.c file /dev/{wd0a,hda} file.c: C program text file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), stripped /dev/wd0a: block special (0/0) /dev/hda: block special (3/0) $ file -s /dev/wd0{b,d} /dev/wd0b: data /dev/wd0d: x86 boot sector $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} /dev/hda: x86 boot sector /dev/hda1: Linux/i386 ext2 filesystem /dev/hda2: x86 boot sector /dev/hda3: x86 boot sector, extended partition table /dev/hda4: Linux/i386 ext2 filesystem /dev/hda5: Linux/i386 swap file /dev/hda6: Linux/i386 swap file /dev/hda7: Linux/i386 swap file /dev/hda8: Linux/i386 swap file /dev/hda9: empty /dev/hda10: empty $ file -i file.c file /dev/{wd0a,hda} file.c: text/x-c file: application/x-executable /dev/hda: application/x-not-regular-file /dev/wd0a: application/x-not-regular-file SEE ALSO top hexdump(1), od(1), strings(1), magic(4) STANDARDS CONFORMANCE top This program is believed to exceed the System V Interface Definition of FILE(CMD), as near as one can determine from the vague language contained therein. Its behavior is mostly compatible with the System V program of the same name. This version knows more magic, however, so it will produce different (albeit more accurate) output in many cases. The one significant difference between this version and System V is that this version treats any white space as a delimiter, so that spaces in pattern strings must be escaped. For example, >10 string language impress (imPRESS data) in an existing magic file would have to be changed to >10 string language\ impress (imPRESS data) In addition, in this version, if a pattern string contains a backslash, it must be escaped. For example 0 string \begindata Andrew Toolkit document in an existing magic file would have to be changed to 0 string \\begindata Andrew Toolkit document SunOS releases 3.2 and later from Sun Microsystems include a command derived from the System V one, but with some extensions. This version differs from Sun's only in minor ways. It includes the extension of the & operator, used as, for example, >16 long&0x7fffffff >0 not stripped SECURITY top On systems where libseccomp (https://github.com/seccomp/libseccomp ) is available, is enforces limiting system calls to only the ones necessary for the operation of the program. This enforcement does not provide any security benefit when is asked to decompress input files running external programs with the -z option. To enable execution of external decompressors, one needs to disable sandboxing using the -S option. MAGIC DIRECTORY top The magic file entries have been collected from various sources, mainly USENET, and contributed by various authors. Christos Zoulas (address below) will collect additional or corrected magic file entries. A consolidation of magic file entries will be distributed periodically. The order of entries in the magic file is significant. Depending on what system you are using, the order that they are put together may be incorrect. If your old command uses a magic file, keep the old magic file around for comparison purposes (rename it to /usr/local/share/misc/magic.orig). HISTORY top There has been a command in every UNIX since at least Research Version 4 (man page dated November, 1973). The System V version introduced one significant major change: the external list of magic types. This slowed the program down slightly but made it a lot more flexible. This program, based on the System V version, was written by Ian Darwin ian@darwinsys.com without looking at anybody else's source code. John Gilmore revised the code extensively, making it better than the first version. Geoff Collyer found several inadequacies and provided some magic file entries. Contributions of the & operator by Rob McMahon, cudcv@warwick.ac.uk, 1989. Guy Harris, guy@netapp.com, made many changes from 1993 to the present. Primary development and maintenance from 1990 to the present by Christos Zoulas christos@astron.com. Altered by Chris Lowth chris@lowth.com, 2000: handle the -i option to output mime type strings, using an alternative magic file and internal logic. Altered by Eric Fischer enf@pobox.com, July, 2000, to identify character codes and attempt to identify the languages of non- ASCII files. Altered by Reuben Thomas rrt@sc3d.org, 2007-2011, to improve MIME support, merge MIME and non-MIME magic, support directories as well as files of magic, apply many bug fixes, update and fix a lot of magic, improve the build system, improve the documentation, and rewrite the Python bindings in pure Python. The list of contributors to the magic directory (magic files) is too long to include here. You know who you are; thank you. Many contributors are listed in the source files. LEGAL NOTICE top Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. Covered by the standard Berkeley Software Distribution copyright; see the file COPYING in the source distribution. The files tar.h and is_tar.c were written by John Gilmore from his public-domain tar(1) program, and are not covered by the above license. BUGS top Please report bugs and send patches to the bug tracker at https://bugs.astron.com/ or the mailing list at file@astron.com (visit https://mailman.astron.com/mailman/listinfo/file first to subscribe). TODO top Fix output so that tests for MIME and APPLE flags are not needed all over the place, and actual output is only done in one place. This needs a design. Suggestion: push possible outputs on to a list, then pick the last-pushed (most specific, one hopes) value at the end, or use a default if the list is empty. This should not slow down evaluation. The handling of MAGIC_CONTINUE and printing \012- between entries is clumsy and complicated; refactor and centralize. Some of the encoding logic is hard-coded in encoding.c and can be moved to the magic files if we had a !:charset annotation. Continue to squash all magic bugs. See Debian BTS for a good source. Store arbitrarily long strings, for example for %s patterns, so that they can be printed out. Fixes Debian bug #271672. This can be done by allocating strings in a string pool, storing the string pool at the end of the magic file and converting all the string pointers to relative offsets from the string pool. Add syntax for relative offsets after current level (Debian bug #466037). Make file -ki work, i.e. give multiple MIME types. Add a zip library so we can peek inside Office2007 documents to print more details about their contents. Add an option to print URLs for the sources of the file descriptions. Combine script searches and add a way to map executable names to MIME types (e.g. have a magic value for !:mime which causes the resulting string to be looked up in a table). This would avoid adding the same magic repeatedly for each new hash-bang interpreter. When a file descriptor is available, we can skip and adjust the buffer instead of the hacky buffer management we do now. Fix name and use to check for consistency at compile time (duplicate name, use pointing to undefined name ). Make name / use more efficient by keeping a sorted list of names. Special-case ^ to flip endianness in the parser so that it does not have to be escaped, and document it. If the offsets specified internally in the file exceed the buffer size ( HOWMANY variable in file.h), then we don't seek to that offset, but we give up. It would be better if buffer managements was done when the file descriptor is available so we can seek around the file. One must be careful though because this has performance and thus security considerations, because one can slow down things by repeatedly seeking. There is support now for keeping separate buffers and having offsets from the end of the file, but the internal buffer management still needs an overhaul. AVAILABILITY top You can obtain the original author's latest version by anonymous FTP on ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz. COLOPHON top This page is part of the file (a file type guesser) project. Information about the project can be found at http://www.darwinsys.com/file/. If you have a bug report for this manual page, see http://bugs.gw.com/my_view_page.php. This page was obtained from the project's upstream Git read-only mirror of the CVS repository https://github.com/glensc/file on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU May 21, 2023 FILE(1) Pages that refer to this page: dh_installmanpages(1), dh_strip(1), ippeveprinter(1), pmcd(1), scr_dump(5), term(5), suffixes(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check md5sum of directory /path against the checksum saved in file 'file' Bash Command:<START>du -csxb /path | md5sum -c file<END>

Check that the master SSH control socket "my-ctrl-socket" to "jm@sampledomain.com" is running

ssh -S my-ctrl-socket -O check jm@sampledomain.com

['ssh']

Output a Bash command to accomplish the following task. Task: Check that the master SSH control socket "my-ctrl-socket" to "jm@sampledomain.com" is running Bash Command:<START>ssh -S my-ctrl-socket -O check jm@sampledomain.com<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # ssh\n\n> Secure Shell is a protocol used to securely log onto remote systems.\n> It can be used for logging or executing commands on a remote server.\n> More information: <https://man.openbsd.org/ssh>.\n\n- Connect to a remote server:\n\n`ssh {{username}}@{{remote_host}}`\n\n- Connect to a remote server with a specific identity (private key):\n\n`ssh -i {{path/to/key_file}} {{username}}@{{remote_host}}`\n\n- Connect to a remote server using a specific [p]ort:\n\n`ssh {{username}}@{{remote_host}} -p {{2222}}`\n\n- Run a command on a remote server with a [t]ty allocation allowing interaction with the remote command:\n\n`ssh {{username}}@{{remote_host}} -t {{command}} {{command_arguments}}`\n\n- SSH tunneling: [D]ynamic port forwarding (SOCKS proxy on `localhost:1080`):\n\n`ssh -D {{1080}} {{username}}@{{remote_host}}`\n\n- SSH tunneling: Forward a specific port (`localhost:9999` to `example.org:80`) along with disabling pseudo-[T]ty allocation and executio[N] of remote commands:\n\n`ssh -L {{9999}}:{{example.org}}:{{80}} -N -T {{username}}@{{remote_host}}`\n\n- SSH [J]umping: Connect through a jumphost to a remote server (Multiple jump hops may be specified separated by comma characters):\n\n`ssh -J {{username}}@{{jump_host}} {{username}}@{{remote_host}}`\n\n- Agent forwarding: Forward the authentication information to the remote machine (see `man ssh_config` for available options):\n\n`ssh -A {{username}}@{{remote_host}}`\n Task: Check that the master SSH control socket "my-ctrl-socket" to "jm@sampledomain.com" is running Bash Command:<START>ssh -S my-ctrl-socket -O check jm@sampledomain.com<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: ssh(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training ssh(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHENTICATION | ESCAPE CHARACTERS | TCP FORWARDING | X11 FORWARDING | VERIFYING HOST KEYS | SSH-BASED VIRTUAL PRIVATE NETWORKS | ENVIRONMENT | FILES | EXIT STATUS | SEE ALSO | STANDARDS | AUTHORS | COLOPHON SSH(1) General Commands Manual SSH(1) NAME top ssh OpenSSH remote login client SYNOPSIS top ssh [-46AaCfGgKkMNnqsTtVvXxYy] [-B bind_interface] [-b bind_address] [-c cipher_spec] [-D [bind_address:]port] [-E log_file] [-e escape_char] [-F configfile] [-I pkcs11] [-i identity_file] [-J destination] [-L address] [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-P tag] [-p port] [-R address] [-S ctl_path] [-W host:port] [-w local_tun[:remote_tun]] destination [command [argument ...]] [-Q query_option] DESCRIPTION top (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine. It is intended to provide secure encrypted communications between two untrusted hosts over an insecure network. X11 connections, arbitrary TCP ports and Unix-domain sockets can also be forwarded over the secure channel. connects and logs into the specified destination, which may be specified as either [user@]hostname or a URI of the form ssh://[user@]hostname[:port]. The user must prove their identity to the remote machine using one of several methods (see below). If a command is specified, it will be executed on the remote host instead of a login shell. A complete command line may be specified as command, or it may have additional arguments. If supplied, the arguments will be appended to the command, separated by spaces, before it is sent to the server to be executed. The options are as follows: -4 Forces to use IPv4 addresses only. -6 Forces to use IPv6 addresses only. -A Enables forwarding of connections from an authentication agent such as ssh-agent(1). This can also be specified on a per-host basis in a configuration file. Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the agent's Unix-domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. A safer alternative may be to use a jump host (see -J). -a Disables forwarding of the authentication agent connection. -B bind_interface Bind to the address of bind_interface before attempting to connect to the destination host. This is only useful on systems with more than one address. -b bind_address Use bind_address on the local machine as the source address of the connection. Only useful on systems with more than one address. -C Requests compression of all data (including stdin, stdout, stderr, and data for forwarded X11, TCP and Unix-domain connections). The compression algorithm is the same used by gzip(1). Compression is desirable on modem lines and other slow connections, but will only slow down things on fast networks. The default value can be set on a host-by-host basis in the configuration files; see the Compression option in ssh_config(5). -c cipher_spec Selects the cipher specification for encrypting the session. cipher_spec is a comma-separated list of ciphers listed in order of preference. See the Ciphers keyword in ssh_config(5) for more information. -D [bind_address:]port Specifies a local dynamic application-level port forwarding. This works by allocating a socket to listen to port on the local side, optionally bound to the specified bind_address. Whenever a connection is made to this port, the connection is forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. Currently the SOCKS4 and SOCKS5 protocols are supported, and will act as a SOCKS server. Only root can forward privileged ports. Dynamic port forwardings can also be specified in the configuration file. IPv6 addresses can be specified by enclosing the address in square brackets. Only the superuser can forward privileged ports. By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address of localhost indicates that the listening port be bound for local use only, while an empty address or * indicates that the port should be available from all interfaces. -E log_file Append debug logs to log_file instead of standard error. -e escape_char Sets the escape character for sessions with a pty (default: ~). The escape character is only recognized at the beginning of a line. The escape character followed by a dot (.) closes the connection; followed by control-Z suspends the connection; and followed by itself sends the escape character once. Setting the character to none disables any escapes and makes the session fully transparent. -F configfile Specifies an alternative per-user configuration file. If a configuration file is given on the command line, the system-wide configuration file (/etc/ssh/ssh_config) will be ignored. The default for the per-user configuration file is ~/.ssh/config. If set to none, no configuration files will be read. -f Requests to go to background just before command execution. This is useful if is going to ask for passwords or passphrases, but the user wants it in the background. This implies -n. The recommended way to start X11 programs at a remote site is with something like ssh -f host xterm. If the ExitOnForwardFailure configuration option is set to yes, then a client started with -f will wait for all remote port forwards to be successfully established before placing itself in the background. Refer to the description of ForkAfterAuthentication in ssh_config(5) for details. -G Causes to print its configuration after evaluating Host and Match blocks and exit. -g Allows remote hosts to connect to local forwarded ports. If used on a multiplexed connection, then this option must be specified on the master process. -I pkcs11 Specify the PKCS#11 shared library should use to communicate with a PKCS#11 token providing keys for user authentication. -i identity_file Selects a file from which the identity (private key) for public key authentication is read. You can also specify a public key file to use the corresponding private key that is loaded in ssh-agent(1) when the private key file is not present locally. The default is ~/.ssh/id_rsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ecdsa_sk, ~/.ssh/id_ed25519, ~/.ssh/id_ed25519_sk and ~/.ssh/id_dsa. Identity files may also be specified on a per-host basis in the configuration file. It is possible to have multiple -i options (and multiple identities specified in configuration files). If no certificates have been explicitly specified by the CertificateFile directive, will also try to load certificate information from the filename obtained by appending -cert.pub to identity filenames. -J destination Connect to the target host by first making an connection to the jump host described by destination and then establishing a TCP forwarding to the ultimate destination from there. Multiple jump hops may be specified separated by comma characters. This is a shortcut to specify a ProxyJump configuration directive. Note that configuration directives supplied on the command-line generally apply to the destination host and not any specified jump hosts. Use ~/.ssh/config to specify configuration for jump hosts. -K Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI credentials to the server. -k Disables forwarding (delegation) of GSSAPI credentials to the server. -L [bind_address:]port:host:hostport -L [bind_address:]port:remote_socket -L local_socket:host:hostport -L local_socket:remote_socket Specifies that connections to the given TCP port or Unix socket on the local (client) host are to be forwarded to the given host and port, or Unix socket, on the remote side. This works by allocating a socket to listen to either a TCP port on the local side, optionally bound to the specified bind_address, or to a Unix socket. Whenever a connection is made to the local port or socket, the connection is forwarded over the secure channel, and a connection is made to either host port hostport, or the Unix socket remote_socket, from the remote machine. Port forwardings can also be specified in the configuration file. Only the superuser can forward privileged ports. IPv6 addresses can be specified by enclosing the address in square brackets. By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address of localhost indicates that the listening port be bound for local use only, while an empty address or * indicates that the port should be available from all interfaces. -l login_name Specifies the user to log in as on the remote machine. This also may be specified on a per-host basis in the configuration file. -M Places the client into master mode for connection sharing. Multiple -M options places into master mode but with confirmation required using ssh-askpass(1) before each operation that changes the multiplexing state (e.g. opening a new session). Refer to the description of ControlMaster in ssh_config(5) for details. -m mac_spec A comma-separated list of MAC (message authentication code) algorithms, specified in order of preference. See the MACs keyword in ssh_config(5) for more information. -N Do not execute a remote command. This is useful for just forwarding ports. Refer to the description of SessionType in ssh_config(5) for details. -n Redirects stdin from /dev/null (actually, prevents reading from stdin). This must be used when is run in the background. A common trick is to use this to run X11 programs on a remote machine. For example, ssh -n shadows.cs.hut.fi emacs & will start an emacs on shadows.cs.hut.fi, and the X11 connection will be automatically forwarded over an encrypted channel. The program will be put in the background. (This does not work if needs to ask for a password or passphrase; see also the -f option.) Refer to the description of StdinNull in ssh_config(5) for details. -O ctl_cmd Control an active connection multiplexing master process. When the -O option is specified, the ctl_cmd argument is interpreted and passed to the master process. Valid commands are: check (check that the master process is running), forward (request forwardings without command execution), cancel (cancel forwardings), exit (request the master to exit), and stop (request the master to stop accepting further multiplexing requests). -o option Can be used to give options in the format used in the configuration file. This is useful for specifying options for which there is no separate command-line flag. For full details of the options listed below, and their possible values, see ssh_config(5). AddKeysToAgent AddressFamily BatchMode BindAddress CanonicalDomains CanonicalizeFallbackLocal CanonicalizeHostname CanonicalizeMaxDots CanonicalizePermittedCNAMEs CASignatureAlgorithms CertificateFile CheckHostIP Ciphers ClearAllForwardings Compression ConnectionAttempts ConnectTimeout ControlMaster ControlPath ControlPersist DynamicForward EnableEscapeCommandline EscapeChar ExitOnForwardFailure FingerprintHash ForkAfterAuthentication ForwardAgent ForwardX11 ForwardX11Timeout ForwardX11Trusted GatewayPorts GlobalKnownHostsFile GSSAPIAuthentication GSSAPIDelegateCredentials HashKnownHosts Host HostbasedAcceptedAlgorithms HostbasedAuthentication HostKeyAlgorithms HostKeyAlias Hostname IdentitiesOnly IdentityAgent IdentityFile IPQoS KbdInteractiveAuthentication KbdInteractiveDevices KexAlgorithms KnownHostsCommand LocalCommand LocalForward LogLevel MACs Match NoHostAuthenticationForLocalhost NumberOfPasswordPrompts PasswordAuthentication PermitLocalCommand PermitRemoteOpen PKCS11Provider Port PreferredAuthentications ProxyCommand ProxyJump ProxyUseFdpass PubkeyAcceptedAlgorithms PubkeyAuthentication RekeyLimit RemoteCommand RemoteForward RequestTTY RequiredRSASize SendEnv ServerAliveInterval ServerAliveCountMax SessionType SetEnv StdinNull StreamLocalBindMask StreamLocalBindUnlink StrictHostKeyChecking TCPKeepAlive Tunnel TunnelDevice UpdateHostKeys User UserKnownHostsFile VerifyHostKeyDNS VisualHostKey XAuthLocation -P tag Specify a tag name that may be used to select configuration in ssh_config(5). Refer to the Tag and Match keywords in ssh_config(5) for more information. -p port Port to connect to on the remote host. This can be specified on a per-host basis in the configuration file. -Q query_option Queries for the algorithms supported by one of the following features: cipher (supported symmetric ciphers), cipher-auth (supported symmetric ciphers that support authenticated encryption), help (supported query terms for use with the -Q flag), mac (supported message integrity codes), kex (key exchange algorithms), key (key types), key-ca-sign (valid CA signature algorithms for certificates), key-cert (certificate key types), key-plain (non-certificate key types), key-sig (all key types and signature algorithms), protocol-version (supported SSH protocol versions), and sig (supported signature algorithms). Alternatively, any keyword from ssh_config(5) or sshd_config(5) that takes an algorithm list may be used as an alias for the corresponding query_option. -q Quiet mode. Causes most warning and diagnostic messages to be suppressed. -R [bind_address:]port:host:hostport -R [bind_address:]port:local_socket -R remote_socket:host:hostport -R remote_socket:local_socket -R [bind_address:]port Specifies that connections to the given TCP port or Unix socket on the remote (server) host are to be forwarded to the local side. This works by allocating a socket to listen to either a TCP port or to a Unix socket on the remote side. Whenever a connection is made to this port or Unix socket, the connection is forwarded over the secure channel, and a connection is made from the local machine to either an explicit destination specified by host port hostport, or local_socket, or, if no explicit destination was specified, will act as a SOCKS 4/5 proxy and forward connections to the destinations requested by the remote SOCKS client. Port forwardings can also be specified in the configuration file. Privileged ports can be forwarded only when logging in as root on the remote machine. IPv6 addresses can be specified by enclosing the address in square brackets. By default, TCP listening sockets on the server will be bound to the loopback interface only. This may be overridden by specifying a bind_address. An empty bind_address, or the address *, indicates that the remote socket should listen on all interfaces. Specifying a remote bind_address will only succeed if the server's GatewayPorts option is enabled (see sshd_config(5)). If the port argument is 0, the listen port will be dynamically allocated on the server and reported to the client at run time. When used together with -O forward, the allocated port will be printed to the standard output. -S ctl_path Specifies the location of a control socket for connection sharing, or the string none to disable connection sharing. Refer to the description of ControlPath and ControlMaster in ssh_config(5) for details. -s May be used to request invocation of a subsystem on the remote system. Subsystems facilitate the use of SSH as a secure transport for other applications (e.g. sftp(1)). The subsystem is specified as the remote command. Refer to the description of SessionType in ssh_config(5) for details. -T Disable pseudo-terminal allocation. -t Force pseudo-terminal allocation. This can be used to execute arbitrary screen-based programs on a remote machine, which can be very useful, e.g. when implementing menu services. Multiple -t options force tty allocation, even if has no local tty. -V Display the version number and exit. -v Verbose mode. Causes to print debugging messages about its progress. This is helpful in debugging connection, authentication, and configuration problems. Multiple -v options increase the verbosity. The maximum is 3. -W host:port Requests that standard input and output on the client be forwarded to host on port over the secure channel. Implies -N, -T, ExitOnForwardFailure and ClearAllForwardings, though these can be overridden in the configuration file or using -o command line options. -w local_tun[:remote_tun] Requests tunnel device forwarding with the specified tun(4) devices between the client (local_tun) and the server (remote_tun). The devices may be specified by numerical ID or the keyword any, which uses the next available tunnel device. If remote_tun is not specified, it defaults to any. See also the Tunnel and TunnelDevice directives in ssh_config(5). If the Tunnel directive is unset, it will be set to the default tunnel mode, which is point-to-point. If a different Tunnel forwarding mode it desired, then it should be specified before -w. -X Enables X11 forwarding. This can also be specified on a per-host basis in a configuration file. X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user's X authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring. For this reason, X11 forwarding is subjected to X11 SECURITY extension restrictions by default. Refer to the -Y option and the ForwardX11Trusted directive in ssh_config(5) for more information. -x Disables X11 forwarding. -Y Enables trusted X11 forwarding. Trusted X11 forwardings are not subjected to the X11 SECURITY extension controls. -y Send log information using the syslog(3) system module. By default this information is sent to stderr. may additionally obtain configuration data from a per-user configuration file and a system-wide configuration file. The file format and configuration options are described in ssh_config(5). AUTHENTICATION top The OpenSSH SSH client supports SSH protocol 2. The methods available for authentication are: GSSAPI-based authentication, host-based authentication, public key authentication, keyboard-interactive authentication, and password authentication. Authentication methods are tried in the order specified above, though PreferredAuthentications can be used to change the default order. Host-based authentication works as follows: If the machine the user logs in from is listed in /etc/hosts.equiv or /etc/shosts.equiv on the remote machine, the user is non-root and the user names are the same on both sides, or if the files ~/.rhosts or ~/.shosts exist in the user's home directory on the remote machine and contain a line containing the name of the client machine and the name of the user on that machine, the user is considered for login. Additionally, the server must be able to verify the client's host key (see the description of /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts, below) for login to be permitted. This authentication method closes security holes due to IP spoofing, DNS spoofing, and routing spoofing. [Note to the administrator: /etc/hosts.equiv, ~/.rhosts, and the rlogin/rsh protocol in general, are inherently insecure and should be disabled if security is desired.] Public key authentication works as follows: The scheme is based on public-key cryptography, using cryptosystems where encryption and decryption are done using separate keys, and it is unfeasible to derive the decryption key from the encryption key. The idea is that each user creates a public/private key pair for authentication purposes. The server knows the public key, and only the user knows the private key. implements public key authentication protocol automatically, using one of the DSA, ECDSA, Ed25519 or RSA algorithms. The HISTORY section of ssl(8) contains a brief discussion of the DSA and RSA algorithms. The file ~/.ssh/authorized_keys lists the public keys that are permitted for logging in. When the user logs in, the program tells the server which key pair it would like to use for authentication. The client proves that it has access to the private key and the server checks that the corresponding public key is authorized to accept the account. The server may inform the client of errors that prevented public key authentication from succeeding after authentication completes using a different method. These may be viewed by increasing the LogLevel to DEBUG or higher (e.g. by using the -v flag). The user creates their key pair by running ssh-keygen(1). This stores the private key in ~/.ssh/id_dsa (DSA), ~/.ssh/id_ecdsa (ECDSA), ~/.ssh/id_ecdsa_sk (authenticator-hosted ECDSA), ~/.ssh/id_ed25519 (Ed25519), ~/.ssh/id_ed25519_sk (authenticator- hosted Ed25519), or ~/.ssh/id_rsa (RSA) and stores the public key in ~/.ssh/id_dsa.pub (DSA), ~/.ssh/id_ecdsa.pub (ECDSA), ~/.ssh/id_ecdsa_sk.pub (authenticator-hosted ECDSA), ~/.ssh/id_ed25519.pub (Ed25519), ~/.ssh/id_ed25519_sk.pub (authenticator-hosted Ed25519), or ~/.ssh/id_rsa.pub (RSA) in the user's home directory. The user should then copy the public key to ~/.ssh/authorized_keys in their home directory on the remote machine. The authorized_keys file corresponds to the conventional ~/.rhosts file, and has one key per line, though the lines can be very long. After this, the user can log in without giving the password. A variation on public key authentication is available in the form of certificate authentication: instead of a set of public/private keys, signed certificates are used. This has the advantage that a single trusted certification authority can be used in place of many public/private keys. See the CERTIFICATES section of ssh-keygen(1) for more information. The most convenient way to use public key or certificate authentication may be with an authentication agent. See ssh-agent(1) and (optionally) the AddKeysToAgent directive in ssh_config(5) for more information. Keyboard-interactive authentication works as follows: The server sends an arbitrary "challenge" text and prompts for a response, possibly multiple times. Examples of keyboard-interactive authentication include BSD Authentication (see login.conf(5)) and PAM (some non-OpenBSD systems). Finally, if other authentication methods fail, prompts the user for a password. The password is sent to the remote host for checking; however, since all communications are encrypted, the password cannot be seen by someone listening on the network. automatically maintains and checks a database containing identification for all hosts it has ever been used with. Host keys are stored in ~/.ssh/known_hosts in the user's home directory. Additionally, the file /etc/ssh/ssh_known_hosts is automatically checked for known hosts. Any new hosts are automatically added to the user's file. If a host's identification ever changes, warns about this and disables password authentication to prevent server spoofing or man-in-the- middle attacks, which could otherwise be used to circumvent the encryption. The StrictHostKeyChecking option can be used to control logins to machines whose host key is not known or has changed. When the user's identity has been accepted by the server, the server either executes the given command in a non-interactive session or, if no command has been specified, logs into the machine and gives the user a normal shell as an interactive session. All communication with the remote command or shell will be automatically encrypted. If an interactive session is requested, by default will only request a pseudo-terminal (pty) for interactive sessions when the client has one. The flags -T and -t can be used to override this behaviour. If a pseudo-terminal has been allocated, the user may use the escape characters noted below. If no pseudo-terminal has been allocated, the session is transparent and can be used to reliably transfer binary data. On most systems, setting the escape character to none will also make the session transparent even if a tty is used. The session terminates when the command or shell on the remote machine exits and all X11 and TCP connections have been closed. ESCAPE CHARACTERS top When a pseudo-terminal has been requested, supports a number of functions through the use of an escape character. A single tilde character can be sent as ~~ or by following the tilde by a character other than those described below. The escape character must always follow a newline to be interpreted as special. The escape character can be changed in configuration files using the EscapeChar configuration directive or on the command line by the -e option. The supported escapes (assuming the default ~) are: ~. Disconnect. ~^Z Background . ~# List forwarded connections. ~& Background at logout when waiting for forwarded connection / X11 sessions to terminate. ~? Display a list of escape characters. ~B Send a BREAK to the remote system (only useful if the peer supports it). ~C Open command line. Currently this allows the addition of port forwardings using the -L, -R and -D options (see above). It also allows the cancellation of existing port-forwardings with -KL[bind_address:]port for local, -KR[bind_address:]port for remote and -KD[bind_address:]port for dynamic port-forwardings. !command allows the user to execute a local command if the PermitLocalCommand option is enabled in ssh_config(5). Basic help is available, using the -h option. ~R Request rekeying of the connection (only useful if the peer supports it). ~V Decrease the verbosity (LogLevel) when errors are being written to stderr. ~v Increase the verbosity (LogLevel) when errors are being written to stderr. TCP FORWARDING top Forwarding of arbitrary TCP connections over a secure channel can be specified either on the command line or in a configuration file. One possible application of TCP forwarding is a secure connection to a mail server; another is going through firewalls. In the example below, we look at encrypting communication for an IRC client, even though the IRC server it connects to does not directly support encrypted communication. This works as follows: the user connects to the remote host using , specifying the ports to be used to forward the connection. After that it is possible to start the program locally, and will encrypt and forward the connection to the remote server. The following example tunnels an IRC session from the client to an IRC server at server.example.com, joining channel #users, nickname pinky, using the standard IRC port, 6667: $ ssh -f -L 6667:localhost:6667 server.example.com sleep 10 $ irc -c '#users' pinky IRC/127.0.0.1 The -f option backgrounds and the remote command sleep 10 is specified to allow an amount of time (10 seconds, in the example) to start the program which is going to use the tunnel. If no connections are made within the time specified, will exit. X11 FORWARDING top If the ForwardX11 variable is set to yes (or see the description of the -X, -x, and -Y options above) and the user is using X11 (the DISPLAY environment variable is set), the connection to the X11 display is automatically forwarded to the remote side in such a way that any X11 programs started from the shell (or command) will go through the encrypted channel, and the connection to the real X server will be made from the local machine. The user should not manually set DISPLAY. Forwarding of X11 connections can be configured on the command line or in configuration files. The DISPLAY value set by will point to the server machine, but with a display number greater than zero. This is normal, and happens because creates a proxy X server on the server machine for forwarding the connections over the encrypted channel. will also automatically set up Xauthority data on the server machine. For this purpose, it will generate a random authorization cookie, store it in Xauthority on the server, and verify that any forwarded connections carry this cookie and replace it by the real cookie when the connection is opened. The real authentication cookie is never sent to the server machine (and no cookies are sent in the plain). If the ForwardAgent variable is set to yes (or see the description of the -A and -a options above) and the user is using an authentication agent, the connection to the agent is automatically forwarded to the remote side. VERIFYING HOST KEYS top When connecting to a server for the first time, a fingerprint of the server's public key is presented to the user (unless the option StrictHostKeyChecking has been disabled). Fingerprints can be determined using ssh-keygen(1): $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key If the fingerprint is already known, it can be matched and the key can be accepted or rejected. If only legacy (MD5) fingerprints for the server are available, the ssh-keygen(1) -E option may be used to downgrade the fingerprint algorithm to match. Because of the difficulty of comparing host keys just by looking at fingerprint strings, there is also support to compare host keys visually, using random art. By setting the VisualHostKey option to yes, a small ASCII graphic gets displayed on every login to a server, no matter if the session itself is interactive or not. By learning the pattern a known server produces, a user can easily find out that the host key has changed when a completely different pattern is displayed. Because these patterns are not unambiguous however, a pattern that looks similar to the pattern remembered only gives a good probability that the host key is the same, not guaranteed proof. To get a listing of the fingerprints along with their random art for all known hosts, the following command line can be used: $ ssh-keygen -lv -f ~/.ssh/known_hosts If the fingerprint is unknown, an alternative method of verification is available: SSH fingerprints verified by DNS. An additional resource record (RR), SSHFP, is added to a zonefile and the connecting client is able to match the fingerprint with that of the key presented. In this example, we are connecting a client to a server, host.example.com. The SSHFP resource records should first be added to the zonefile for host.example.com: $ ssh-keygen -r host.example.com. The output lines will have to be added to the zonefile. To check that the zone is answering fingerprint queries: $ dig -t SSHFP host.example.com Finally the client connects: $ ssh -o "VerifyHostKeyDNS ask" host.example.com [...] Matching host key fingerprint found in DNS. Are you sure you want to continue connecting (yes/no)? See the VerifyHostKeyDNS option in ssh_config(5) for more information. SSH-BASED VIRTUAL PRIVATE NETWORKS top contains support for Virtual Private Network (VPN) tunnelling using the tun(4) network pseudo-device, allowing two networks to be joined securely. The sshd_config(5) configuration option PermitTunnel controls whether the server supports this, and at what level (layer 2 or 3 traffic). The following example would connect client network 10.0.50.0/24 with remote network 10.0.99.0/24 using a point-to-point connection from 10.1.1.1 to 10.1.1.2, provided that the SSH server running on the gateway to the remote network, at 192.168.1.15, allows it. On the client: # ssh -f -w 0:1 192.168.1.15 true # ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252 # route add 10.0.99.0/24 10.1.1.2 On the server: # ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252 # route add 10.0.50.0/24 10.1.1.1 Client access may be more finely tuned via the /root/.ssh/authorized_keys file (see below) and the PermitRootLogin server option. The following entry would permit connections on tun(4) device 1 from user jane and on tun device 2 from user john, if PermitRootLogin is set to forced-commands-only: tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john Since an SSH-based setup entails a fair amount of overhead, it may be more suited to temporary setups, such as for wireless VPNs. More permanent VPNs are better provided by tools such as ipsecctl(8) and isakmpd(8). ENVIRONMENT top will normally set the following environment variables: DISPLAY The DISPLAY variable indicates the location of the X11 server. It is automatically set by to point to a value of the form hostname:n, where hostname indicates the host where the shell runs, and n is an integer 1. uses this special value to forward X11 connections over the secure channel. The user should normally not set DISPLAY explicitly, as that will render the X11 connection insecure (and will require the user to manually copy any required authorization cookies). HOME Set to the path of the user's home directory. LOGNAME Synonym for USER; set for compatibility with systems that use this variable. MAIL Set to the path of the user's mailbox. PATH Set to the default PATH, as specified when compiling . SSH_ASKPASS If needs a passphrase, it will read the passphrase from the current terminal if it was run from a terminal. If does not have a terminal associated with it but DISPLAY and SSH_ASKPASS are set, it will execute the program specified by SSH_ASKPASS and open an X11 window to read the passphrase. This is particularly useful when calling from a .xsession or related script. (Note that on some machines it may be necessary to redirect the input from /dev/null to make this work.) SSH_ASKPASS_REQUIRE Allows further control over the use of an askpass program. If this variable is set to never then will never attempt to use one. If it is set to prefer, then will prefer to use the askpass program instead of the TTY when requesting passwords. Finally, if the variable is set to force, then the askpass program will be used for all passphrase input regardless of whether DISPLAY is set. SSH_AUTH_SOCK Identifies the path of a Unix-domain socket used to communicate with the agent. SSH_CONNECTION Identifies the client and server ends of the connection. The variable contains four space-separated values: client IP address, client port number, server IP address, and server port number. SSH_ORIGINAL_COMMAND This variable contains the original command line if a forced command is executed. It can be used to extract the original arguments. SSH_TTY This is set to the name of the tty (path to the device) associated with the current shell or command. If the current session has no tty, this variable is not set. SSH_TUNNEL Optionally set by sshd(8) to contain the interface names assigned if tunnel forwarding was requested by the client. SSH_USER_AUTH Optionally set by sshd(8), this variable may contain a pathname to a file that lists the authentication methods successfully used when the session was established, including any public keys that were used. TZ This variable is set to indicate the present time zone if it was set when the daemon was started (i.e. the daemon passes the value on to new connections). USER Set to the name of the user logging in. Additionally, reads ~/.ssh/environment, and adds lines of the format VARNAME=value to the environment if the file exists and users are allowed to change their environment. For more information, see the PermitUserEnvironment option in sshd_config(5). FILES top ~/.rhosts This file is used for host-based authentication (see above). On some machines this file may need to be world- readable if the user's home directory is on an NFS partition, because sshd(8) reads it as root. Additionally, this file must be owned by the user, and must not have write permissions for anyone else. The recommended permission for most machines is read/write for the user, and not accessible by others. ~/.shosts This file is used in exactly the same way as .rhosts, but allows host-based authentication without permitting login with rlogin/rsh. ~/.ssh/ This directory is the default location for all user- specific configuration and authentication information. There is no general requirement to keep the entire contents of this directory secret, but the recommended permissions are read/write/execute for the user, and not accessible by others. ~/.ssh/authorized_keys Lists the public keys (DSA, ECDSA, Ed25519, RSA) that can be used for logging in as this user. The format of this file is described in the sshd(8) manual page. This file is not highly sensitive, but the recommended permissions are read/write for the user, and not accessible by others. ~/.ssh/config This is the per-user configuration file. The file format and configuration options are described in ssh_config(5). Because of the potential for abuse, this file must have strict permissions: read/write for the user, and not writable by others. ~/.ssh/environment Contains additional definitions for environment variables; see ENVIRONMENT, above. ~/.ssh/id_dsa ~/.ssh/id_ecdsa ~/.ssh/id_ecdsa_sk ~/.ssh/id_ed25519 ~/.ssh/id_ed25519_sk ~/.ssh/id_rsa Contains the private key for authentication. These files contain sensitive data and should be readable by the user but not accessible by others (read/write/execute). will simply ignore a private key file if it is accessible by others. It is possible to specify a passphrase when generating the key which will be used to encrypt the sensitive part of this file using AES-128. ~/.ssh/id_dsa.pub ~/.ssh/id_ecdsa.pub ~/.ssh/id_ecdsa_sk.pub ~/.ssh/id_ed25519.pub ~/.ssh/id_ed25519_sk.pub ~/.ssh/id_rsa.pub Contains the public key for authentication. These files are not sensitive and can (but need not) be readable by anyone. ~/.ssh/known_hosts Contains a list of host keys for all hosts the user has logged into that are not already in the systemwide list of known host keys. See sshd(8) for further details of the format of this file. ~/.ssh/rc Commands in this file are executed by when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information. /etc/hosts.equiv This file is for host-based authentication (see above). It should only be writable by root. /etc/shosts.equiv This file is used in exactly the same way as hosts.equiv, but allows host-based authentication without permitting login with rlogin/rsh. /etc/ssh/ssh_config Systemwide configuration file. The file format and configuration options are described in ssh_config(5). /etc/ssh/ssh_host_key /etc/ssh/ssh_host_dsa_key /etc/ssh/ssh_host_ecdsa_key /etc/ssh/ssh_host_ed25519_key /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys and are used for host-based authentication. /etc/ssh/ssh_known_hosts Systemwide list of known host keys. This file should be prepared by the system administrator to contain the public host keys of all machines in the organization. It should be world-readable. See sshd(8) for further details of the format of this file. /etc/ssh/sshrc Commands in this file are executed by when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information. EXIT STATUS top exits with the exit status of the remote command or with 255 if an error occurred. SEE ALSO top scp(1), sftp(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), ssh-keyscan(1), tun(4), ssh_config(5), ssh-keysign(8), sshd(8) STANDARDS top S. Lehtinen and C. Lonvick, The Secure Shell (SSH) Protocol Assigned Numbers, RFC 4250, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Protocol Architecture, RFC 4251, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Authentication Protocol, RFC 4252, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Transport Layer Protocol, RFC 4253, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Connection Protocol, RFC 4254, January 2006. J. Schlyter and W. Griffin, Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints, RFC 4255, January 2006. F. Cusack and M. Forssen, Generic Message Exchange Authentication for the Secure Shell Protocol (SSH), RFC 4256, January 2006. J. Galbraith and P. Remaker, The Secure Shell (SSH) Session Channel Break Extension, RFC 4335, January 2006. M. Bellare, T. Kohno, and C. Namprempre, The Secure Shell (SSH) Transport Layer Encryption Modes, RFC 4344, January 2006. B. Harris, Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol, RFC 4345, January 2006. M. Friedl, N. Provos, and W. Simpson, Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol, RFC 4419, March 2006. J. Galbraith and R. Thayer, The Secure Shell (SSH) Public Key File Format, RFC 4716, November 2006. D. Stebila and J. Green, Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer, RFC 5656, December 2009. A. Perrig and D. Song, Hash Visualization: a New Technique to improve Real-World Security, 1999, International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99). AUTHORS top OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re- added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. COLOPHON top This page is part of the openssh (Portable OpenSSH) project. Information about the project can be found at http://www.openssh.com/portable.html. If you have a bug report for this manual page, see http://www.openssh.com/report.html. This page was obtained from the tarball openssh-9.6p1.tar.gz fetched from http://ftp.eu.openbsd.org/pub/OpenBSD/OpenSSH/portable/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU October 11, 2023 SSH(1) Pages that refer to this page: stap-jupyter(1), systemd-stdio-bridge(1), tar(1), sd_bus_default(3), environment.d(5), proc(5), user@.service(5), pty(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check that the master SSH control socket "my-ctrl-socket" to "jm@sampledomain.com" is running Bash Command:<START>ssh -S my-ctrl-socket -O check jm@sampledomain.com<END>

Check that the master ssh connection "officefirewall" is running

ssh -O check officefirewall

['ssh']

Output a Bash command to accomplish the following task. Task: Check that the master ssh connection "officefirewall" is running Bash Command:<START>ssh -O check officefirewall<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # ssh\n\n> Secure Shell is a protocol used to securely log onto remote systems.\n> It can be used for logging or executing commands on a remote server.\n> More information: <https://man.openbsd.org/ssh>.\n\n- Connect to a remote server:\n\n`ssh {{username}}@{{remote_host}}`\n\n- Connect to a remote server with a specific identity (private key):\n\n`ssh -i {{path/to/key_file}} {{username}}@{{remote_host}}`\n\n- Connect to a remote server using a specific [p]ort:\n\n`ssh {{username}}@{{remote_host}} -p {{2222}}`\n\n- Run a command on a remote server with a [t]ty allocation allowing interaction with the remote command:\n\n`ssh {{username}}@{{remote_host}} -t {{command}} {{command_arguments}}`\n\n- SSH tunneling: [D]ynamic port forwarding (SOCKS proxy on `localhost:1080`):\n\n`ssh -D {{1080}} {{username}}@{{remote_host}}`\n\n- SSH tunneling: Forward a specific port (`localhost:9999` to `example.org:80`) along with disabling pseudo-[T]ty allocation and executio[N] of remote commands:\n\n`ssh -L {{9999}}:{{example.org}}:{{80}} -N -T {{username}}@{{remote_host}}`\n\n- SSH [J]umping: Connect through a jumphost to a remote server (Multiple jump hops may be specified separated by comma characters):\n\n`ssh -J {{username}}@{{jump_host}} {{username}}@{{remote_host}}`\n\n- Agent forwarding: Forward the authentication information to the remote machine (see `man ssh_config` for available options):\n\n`ssh -A {{username}}@{{remote_host}}`\n Task: Check that the master ssh connection "officefirewall" is running Bash Command:<START>ssh -O check officefirewall<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: ssh(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training ssh(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHENTICATION | ESCAPE CHARACTERS | TCP FORWARDING | X11 FORWARDING | VERIFYING HOST KEYS | SSH-BASED VIRTUAL PRIVATE NETWORKS | ENVIRONMENT | FILES | EXIT STATUS | SEE ALSO | STANDARDS | AUTHORS | COLOPHON SSH(1) General Commands Manual SSH(1) NAME top ssh OpenSSH remote login client SYNOPSIS top ssh [-46AaCfGgKkMNnqsTtVvXxYy] [-B bind_interface] [-b bind_address] [-c cipher_spec] [-D [bind_address:]port] [-E log_file] [-e escape_char] [-F configfile] [-I pkcs11] [-i identity_file] [-J destination] [-L address] [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-P tag] [-p port] [-R address] [-S ctl_path] [-W host:port] [-w local_tun[:remote_tun]] destination [command [argument ...]] [-Q query_option] DESCRIPTION top (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine. It is intended to provide secure encrypted communications between two untrusted hosts over an insecure network. X11 connections, arbitrary TCP ports and Unix-domain sockets can also be forwarded over the secure channel. connects and logs into the specified destination, which may be specified as either [user@]hostname or a URI of the form ssh://[user@]hostname[:port]. The user must prove their identity to the remote machine using one of several methods (see below). If a command is specified, it will be executed on the remote host instead of a login shell. A complete command line may be specified as command, or it may have additional arguments. If supplied, the arguments will be appended to the command, separated by spaces, before it is sent to the server to be executed. The options are as follows: -4 Forces to use IPv4 addresses only. -6 Forces to use IPv6 addresses only. -A Enables forwarding of connections from an authentication agent such as ssh-agent(1). This can also be specified on a per-host basis in a configuration file. Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the agent's Unix-domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. A safer alternative may be to use a jump host (see -J). -a Disables forwarding of the authentication agent connection. -B bind_interface Bind to the address of bind_interface before attempting to connect to the destination host. This is only useful on systems with more than one address. -b bind_address Use bind_address on the local machine as the source address of the connection. Only useful on systems with more than one address. -C Requests compression of all data (including stdin, stdout, stderr, and data for forwarded X11, TCP and Unix-domain connections). The compression algorithm is the same used by gzip(1). Compression is desirable on modem lines and other slow connections, but will only slow down things on fast networks. The default value can be set on a host-by-host basis in the configuration files; see the Compression option in ssh_config(5). -c cipher_spec Selects the cipher specification for encrypting the session. cipher_spec is a comma-separated list of ciphers listed in order of preference. See the Ciphers keyword in ssh_config(5) for more information. -D [bind_address:]port Specifies a local dynamic application-level port forwarding. This works by allocating a socket to listen to port on the local side, optionally bound to the specified bind_address. Whenever a connection is made to this port, the connection is forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. Currently the SOCKS4 and SOCKS5 protocols are supported, and will act as a SOCKS server. Only root can forward privileged ports. Dynamic port forwardings can also be specified in the configuration file. IPv6 addresses can be specified by enclosing the address in square brackets. Only the superuser can forward privileged ports. By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address of localhost indicates that the listening port be bound for local use only, while an empty address or * indicates that the port should be available from all interfaces. -E log_file Append debug logs to log_file instead of standard error. -e escape_char Sets the escape character for sessions with a pty (default: ~). The escape character is only recognized at the beginning of a line. The escape character followed by a dot (.) closes the connection; followed by control-Z suspends the connection; and followed by itself sends the escape character once. Setting the character to none disables any escapes and makes the session fully transparent. -F configfile Specifies an alternative per-user configuration file. If a configuration file is given on the command line, the system-wide configuration file (/etc/ssh/ssh_config) will be ignored. The default for the per-user configuration file is ~/.ssh/config. If set to none, no configuration files will be read. -f Requests to go to background just before command execution. This is useful if is going to ask for passwords or passphrases, but the user wants it in the background. This implies -n. The recommended way to start X11 programs at a remote site is with something like ssh -f host xterm. If the ExitOnForwardFailure configuration option is set to yes, then a client started with -f will wait for all remote port forwards to be successfully established before placing itself in the background. Refer to the description of ForkAfterAuthentication in ssh_config(5) for details. -G Causes to print its configuration after evaluating Host and Match blocks and exit. -g Allows remote hosts to connect to local forwarded ports. If used on a multiplexed connection, then this option must be specified on the master process. -I pkcs11 Specify the PKCS#11 shared library should use to communicate with a PKCS#11 token providing keys for user authentication. -i identity_file Selects a file from which the identity (private key) for public key authentication is read. You can also specify a public key file to use the corresponding private key that is loaded in ssh-agent(1) when the private key file is not present locally. The default is ~/.ssh/id_rsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ecdsa_sk, ~/.ssh/id_ed25519, ~/.ssh/id_ed25519_sk and ~/.ssh/id_dsa. Identity files may also be specified on a per-host basis in the configuration file. It is possible to have multiple -i options (and multiple identities specified in configuration files). If no certificates have been explicitly specified by the CertificateFile directive, will also try to load certificate information from the filename obtained by appending -cert.pub to identity filenames. -J destination Connect to the target host by first making an connection to the jump host described by destination and then establishing a TCP forwarding to the ultimate destination from there. Multiple jump hops may be specified separated by comma characters. This is a shortcut to specify a ProxyJump configuration directive. Note that configuration directives supplied on the command-line generally apply to the destination host and not any specified jump hosts. Use ~/.ssh/config to specify configuration for jump hosts. -K Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI credentials to the server. -k Disables forwarding (delegation) of GSSAPI credentials to the server. -L [bind_address:]port:host:hostport -L [bind_address:]port:remote_socket -L local_socket:host:hostport -L local_socket:remote_socket Specifies that connections to the given TCP port or Unix socket on the local (client) host are to be forwarded to the given host and port, or Unix socket, on the remote side. This works by allocating a socket to listen to either a TCP port on the local side, optionally bound to the specified bind_address, or to a Unix socket. Whenever a connection is made to the local port or socket, the connection is forwarded over the secure channel, and a connection is made to either host port hostport, or the Unix socket remote_socket, from the remote machine. Port forwardings can also be specified in the configuration file. Only the superuser can forward privileged ports. IPv6 addresses can be specified by enclosing the address in square brackets. By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address of localhost indicates that the listening port be bound for local use only, while an empty address or * indicates that the port should be available from all interfaces. -l login_name Specifies the user to log in as on the remote machine. This also may be specified on a per-host basis in the configuration file. -M Places the client into master mode for connection sharing. Multiple -M options places into master mode but with confirmation required using ssh-askpass(1) before each operation that changes the multiplexing state (e.g. opening a new session). Refer to the description of ControlMaster in ssh_config(5) for details. -m mac_spec A comma-separated list of MAC (message authentication code) algorithms, specified in order of preference. See the MACs keyword in ssh_config(5) for more information. -N Do not execute a remote command. This is useful for just forwarding ports. Refer to the description of SessionType in ssh_config(5) for details. -n Redirects stdin from /dev/null (actually, prevents reading from stdin). This must be used when is run in the background. A common trick is to use this to run X11 programs on a remote machine. For example, ssh -n shadows.cs.hut.fi emacs & will start an emacs on shadows.cs.hut.fi, and the X11 connection will be automatically forwarded over an encrypted channel. The program will be put in the background. (This does not work if needs to ask for a password or passphrase; see also the -f option.) Refer to the description of StdinNull in ssh_config(5) for details. -O ctl_cmd Control an active connection multiplexing master process. When the -O option is specified, the ctl_cmd argument is interpreted and passed to the master process. Valid commands are: check (check that the master process is running), forward (request forwardings without command execution), cancel (cancel forwardings), exit (request the master to exit), and stop (request the master to stop accepting further multiplexing requests). -o option Can be used to give options in the format used in the configuration file. This is useful for specifying options for which there is no separate command-line flag. For full details of the options listed below, and their possible values, see ssh_config(5). AddKeysToAgent AddressFamily BatchMode BindAddress CanonicalDomains CanonicalizeFallbackLocal CanonicalizeHostname CanonicalizeMaxDots CanonicalizePermittedCNAMEs CASignatureAlgorithms CertificateFile CheckHostIP Ciphers ClearAllForwardings Compression ConnectionAttempts ConnectTimeout ControlMaster ControlPath ControlPersist DynamicForward EnableEscapeCommandline EscapeChar ExitOnForwardFailure FingerprintHash ForkAfterAuthentication ForwardAgent ForwardX11 ForwardX11Timeout ForwardX11Trusted GatewayPorts GlobalKnownHostsFile GSSAPIAuthentication GSSAPIDelegateCredentials HashKnownHosts Host HostbasedAcceptedAlgorithms HostbasedAuthentication HostKeyAlgorithms HostKeyAlias Hostname IdentitiesOnly IdentityAgent IdentityFile IPQoS KbdInteractiveAuthentication KbdInteractiveDevices KexAlgorithms KnownHostsCommand LocalCommand LocalForward LogLevel MACs Match NoHostAuthenticationForLocalhost NumberOfPasswordPrompts PasswordAuthentication PermitLocalCommand PermitRemoteOpen PKCS11Provider Port PreferredAuthentications ProxyCommand ProxyJump ProxyUseFdpass PubkeyAcceptedAlgorithms PubkeyAuthentication RekeyLimit RemoteCommand RemoteForward RequestTTY RequiredRSASize SendEnv ServerAliveInterval ServerAliveCountMax SessionType SetEnv StdinNull StreamLocalBindMask StreamLocalBindUnlink StrictHostKeyChecking TCPKeepAlive Tunnel TunnelDevice UpdateHostKeys User UserKnownHostsFile VerifyHostKeyDNS VisualHostKey XAuthLocation -P tag Specify a tag name that may be used to select configuration in ssh_config(5). Refer to the Tag and Match keywords in ssh_config(5) for more information. -p port Port to connect to on the remote host. This can be specified on a per-host basis in the configuration file. -Q query_option Queries for the algorithms supported by one of the following features: cipher (supported symmetric ciphers), cipher-auth (supported symmetric ciphers that support authenticated encryption), help (supported query terms for use with the -Q flag), mac (supported message integrity codes), kex (key exchange algorithms), key (key types), key-ca-sign (valid CA signature algorithms for certificates), key-cert (certificate key types), key-plain (non-certificate key types), key-sig (all key types and signature algorithms), protocol-version (supported SSH protocol versions), and sig (supported signature algorithms). Alternatively, any keyword from ssh_config(5) or sshd_config(5) that takes an algorithm list may be used as an alias for the corresponding query_option. -q Quiet mode. Causes most warning and diagnostic messages to be suppressed. -R [bind_address:]port:host:hostport -R [bind_address:]port:local_socket -R remote_socket:host:hostport -R remote_socket:local_socket -R [bind_address:]port Specifies that connections to the given TCP port or Unix socket on the remote (server) host are to be forwarded to the local side. This works by allocating a socket to listen to either a TCP port or to a Unix socket on the remote side. Whenever a connection is made to this port or Unix socket, the connection is forwarded over the secure channel, and a connection is made from the local machine to either an explicit destination specified by host port hostport, or local_socket, or, if no explicit destination was specified, will act as a SOCKS 4/5 proxy and forward connections to the destinations requested by the remote SOCKS client. Port forwardings can also be specified in the configuration file. Privileged ports can be forwarded only when logging in as root on the remote machine. IPv6 addresses can be specified by enclosing the address in square brackets. By default, TCP listening sockets on the server will be bound to the loopback interface only. This may be overridden by specifying a bind_address. An empty bind_address, or the address *, indicates that the remote socket should listen on all interfaces. Specifying a remote bind_address will only succeed if the server's GatewayPorts option is enabled (see sshd_config(5)). If the port argument is 0, the listen port will be dynamically allocated on the server and reported to the client at run time. When used together with -O forward, the allocated port will be printed to the standard output. -S ctl_path Specifies the location of a control socket for connection sharing, or the string none to disable connection sharing. Refer to the description of ControlPath and ControlMaster in ssh_config(5) for details. -s May be used to request invocation of a subsystem on the remote system. Subsystems facilitate the use of SSH as a secure transport for other applications (e.g. sftp(1)). The subsystem is specified as the remote command. Refer to the description of SessionType in ssh_config(5) for details. -T Disable pseudo-terminal allocation. -t Force pseudo-terminal allocation. This can be used to execute arbitrary screen-based programs on a remote machine, which can be very useful, e.g. when implementing menu services. Multiple -t options force tty allocation, even if has no local tty. -V Display the version number and exit. -v Verbose mode. Causes to print debugging messages about its progress. This is helpful in debugging connection, authentication, and configuration problems. Multiple -v options increase the verbosity. The maximum is 3. -W host:port Requests that standard input and output on the client be forwarded to host on port over the secure channel. Implies -N, -T, ExitOnForwardFailure and ClearAllForwardings, though these can be overridden in the configuration file or using -o command line options. -w local_tun[:remote_tun] Requests tunnel device forwarding with the specified tun(4) devices between the client (local_tun) and the server (remote_tun). The devices may be specified by numerical ID or the keyword any, which uses the next available tunnel device. If remote_tun is not specified, it defaults to any. See also the Tunnel and TunnelDevice directives in ssh_config(5). If the Tunnel directive is unset, it will be set to the default tunnel mode, which is point-to-point. If a different Tunnel forwarding mode it desired, then it should be specified before -w. -X Enables X11 forwarding. This can also be specified on a per-host basis in a configuration file. X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user's X authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring. For this reason, X11 forwarding is subjected to X11 SECURITY extension restrictions by default. Refer to the -Y option and the ForwardX11Trusted directive in ssh_config(5) for more information. -x Disables X11 forwarding. -Y Enables trusted X11 forwarding. Trusted X11 forwardings are not subjected to the X11 SECURITY extension controls. -y Send log information using the syslog(3) system module. By default this information is sent to stderr. may additionally obtain configuration data from a per-user configuration file and a system-wide configuration file. The file format and configuration options are described in ssh_config(5). AUTHENTICATION top The OpenSSH SSH client supports SSH protocol 2. The methods available for authentication are: GSSAPI-based authentication, host-based authentication, public key authentication, keyboard-interactive authentication, and password authentication. Authentication methods are tried in the order specified above, though PreferredAuthentications can be used to change the default order. Host-based authentication works as follows: If the machine the user logs in from is listed in /etc/hosts.equiv or /etc/shosts.equiv on the remote machine, the user is non-root and the user names are the same on both sides, or if the files ~/.rhosts or ~/.shosts exist in the user's home directory on the remote machine and contain a line containing the name of the client machine and the name of the user on that machine, the user is considered for login. Additionally, the server must be able to verify the client's host key (see the description of /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts, below) for login to be permitted. This authentication method closes security holes due to IP spoofing, DNS spoofing, and routing spoofing. [Note to the administrator: /etc/hosts.equiv, ~/.rhosts, and the rlogin/rsh protocol in general, are inherently insecure and should be disabled if security is desired.] Public key authentication works as follows: The scheme is based on public-key cryptography, using cryptosystems where encryption and decryption are done using separate keys, and it is unfeasible to derive the decryption key from the encryption key. The idea is that each user creates a public/private key pair for authentication purposes. The server knows the public key, and only the user knows the private key. implements public key authentication protocol automatically, using one of the DSA, ECDSA, Ed25519 or RSA algorithms. The HISTORY section of ssl(8) contains a brief discussion of the DSA and RSA algorithms. The file ~/.ssh/authorized_keys lists the public keys that are permitted for logging in. When the user logs in, the program tells the server which key pair it would like to use for authentication. The client proves that it has access to the private key and the server checks that the corresponding public key is authorized to accept the account. The server may inform the client of errors that prevented public key authentication from succeeding after authentication completes using a different method. These may be viewed by increasing the LogLevel to DEBUG or higher (e.g. by using the -v flag). The user creates their key pair by running ssh-keygen(1). This stores the private key in ~/.ssh/id_dsa (DSA), ~/.ssh/id_ecdsa (ECDSA), ~/.ssh/id_ecdsa_sk (authenticator-hosted ECDSA), ~/.ssh/id_ed25519 (Ed25519), ~/.ssh/id_ed25519_sk (authenticator- hosted Ed25519), or ~/.ssh/id_rsa (RSA) and stores the public key in ~/.ssh/id_dsa.pub (DSA), ~/.ssh/id_ecdsa.pub (ECDSA), ~/.ssh/id_ecdsa_sk.pub (authenticator-hosted ECDSA), ~/.ssh/id_ed25519.pub (Ed25519), ~/.ssh/id_ed25519_sk.pub (authenticator-hosted Ed25519), or ~/.ssh/id_rsa.pub (RSA) in the user's home directory. The user should then copy the public key to ~/.ssh/authorized_keys in their home directory on the remote machine. The authorized_keys file corresponds to the conventional ~/.rhosts file, and has one key per line, though the lines can be very long. After this, the user can log in without giving the password. A variation on public key authentication is available in the form of certificate authentication: instead of a set of public/private keys, signed certificates are used. This has the advantage that a single trusted certification authority can be used in place of many public/private keys. See the CERTIFICATES section of ssh-keygen(1) for more information. The most convenient way to use public key or certificate authentication may be with an authentication agent. See ssh-agent(1) and (optionally) the AddKeysToAgent directive in ssh_config(5) for more information. Keyboard-interactive authentication works as follows: The server sends an arbitrary "challenge" text and prompts for a response, possibly multiple times. Examples of keyboard-interactive authentication include BSD Authentication (see login.conf(5)) and PAM (some non-OpenBSD systems). Finally, if other authentication methods fail, prompts the user for a password. The password is sent to the remote host for checking; however, since all communications are encrypted, the password cannot be seen by someone listening on the network. automatically maintains and checks a database containing identification for all hosts it has ever been used with. Host keys are stored in ~/.ssh/known_hosts in the user's home directory. Additionally, the file /etc/ssh/ssh_known_hosts is automatically checked for known hosts. Any new hosts are automatically added to the user's file. If a host's identification ever changes, warns about this and disables password authentication to prevent server spoofing or man-in-the- middle attacks, which could otherwise be used to circumvent the encryption. The StrictHostKeyChecking option can be used to control logins to machines whose host key is not known or has changed. When the user's identity has been accepted by the server, the server either executes the given command in a non-interactive session or, if no command has been specified, logs into the machine and gives the user a normal shell as an interactive session. All communication with the remote command or shell will be automatically encrypted. If an interactive session is requested, by default will only request a pseudo-terminal (pty) for interactive sessions when the client has one. The flags -T and -t can be used to override this behaviour. If a pseudo-terminal has been allocated, the user may use the escape characters noted below. If no pseudo-terminal has been allocated, the session is transparent and can be used to reliably transfer binary data. On most systems, setting the escape character to none will also make the session transparent even if a tty is used. The session terminates when the command or shell on the remote machine exits and all X11 and TCP connections have been closed. ESCAPE CHARACTERS top When a pseudo-terminal has been requested, supports a number of functions through the use of an escape character. A single tilde character can be sent as ~~ or by following the tilde by a character other than those described below. The escape character must always follow a newline to be interpreted as special. The escape character can be changed in configuration files using the EscapeChar configuration directive or on the command line by the -e option. The supported escapes (assuming the default ~) are: ~. Disconnect. ~^Z Background . ~# List forwarded connections. ~& Background at logout when waiting for forwarded connection / X11 sessions to terminate. ~? Display a list of escape characters. ~B Send a BREAK to the remote system (only useful if the peer supports it). ~C Open command line. Currently this allows the addition of port forwardings using the -L, -R and -D options (see above). It also allows the cancellation of existing port-forwardings with -KL[bind_address:]port for local, -KR[bind_address:]port for remote and -KD[bind_address:]port for dynamic port-forwardings. !command allows the user to execute a local command if the PermitLocalCommand option is enabled in ssh_config(5). Basic help is available, using the -h option. ~R Request rekeying of the connection (only useful if the peer supports it). ~V Decrease the verbosity (LogLevel) when errors are being written to stderr. ~v Increase the verbosity (LogLevel) when errors are being written to stderr. TCP FORWARDING top Forwarding of arbitrary TCP connections over a secure channel can be specified either on the command line or in a configuration file. One possible application of TCP forwarding is a secure connection to a mail server; another is going through firewalls. In the example below, we look at encrypting communication for an IRC client, even though the IRC server it connects to does not directly support encrypted communication. This works as follows: the user connects to the remote host using , specifying the ports to be used to forward the connection. After that it is possible to start the program locally, and will encrypt and forward the connection to the remote server. The following example tunnels an IRC session from the client to an IRC server at server.example.com, joining channel #users, nickname pinky, using the standard IRC port, 6667: $ ssh -f -L 6667:localhost:6667 server.example.com sleep 10 $ irc -c '#users' pinky IRC/127.0.0.1 The -f option backgrounds and the remote command sleep 10 is specified to allow an amount of time (10 seconds, in the example) to start the program which is going to use the tunnel. If no connections are made within the time specified, will exit. X11 FORWARDING top If the ForwardX11 variable is set to yes (or see the description of the -X, -x, and -Y options above) and the user is using X11 (the DISPLAY environment variable is set), the connection to the X11 display is automatically forwarded to the remote side in such a way that any X11 programs started from the shell (or command) will go through the encrypted channel, and the connection to the real X server will be made from the local machine. The user should not manually set DISPLAY. Forwarding of X11 connections can be configured on the command line or in configuration files. The DISPLAY value set by will point to the server machine, but with a display number greater than zero. This is normal, and happens because creates a proxy X server on the server machine for forwarding the connections over the encrypted channel. will also automatically set up Xauthority data on the server machine. For this purpose, it will generate a random authorization cookie, store it in Xauthority on the server, and verify that any forwarded connections carry this cookie and replace it by the real cookie when the connection is opened. The real authentication cookie is never sent to the server machine (and no cookies are sent in the plain). If the ForwardAgent variable is set to yes (or see the description of the -A and -a options above) and the user is using an authentication agent, the connection to the agent is automatically forwarded to the remote side. VERIFYING HOST KEYS top When connecting to a server for the first time, a fingerprint of the server's public key is presented to the user (unless the option StrictHostKeyChecking has been disabled). Fingerprints can be determined using ssh-keygen(1): $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key If the fingerprint is already known, it can be matched and the key can be accepted or rejected. If only legacy (MD5) fingerprints for the server are available, the ssh-keygen(1) -E option may be used to downgrade the fingerprint algorithm to match. Because of the difficulty of comparing host keys just by looking at fingerprint strings, there is also support to compare host keys visually, using random art. By setting the VisualHostKey option to yes, a small ASCII graphic gets displayed on every login to a server, no matter if the session itself is interactive or not. By learning the pattern a known server produces, a user can easily find out that the host key has changed when a completely different pattern is displayed. Because these patterns are not unambiguous however, a pattern that looks similar to the pattern remembered only gives a good probability that the host key is the same, not guaranteed proof. To get a listing of the fingerprints along with their random art for all known hosts, the following command line can be used: $ ssh-keygen -lv -f ~/.ssh/known_hosts If the fingerprint is unknown, an alternative method of verification is available: SSH fingerprints verified by DNS. An additional resource record (RR), SSHFP, is added to a zonefile and the connecting client is able to match the fingerprint with that of the key presented. In this example, we are connecting a client to a server, host.example.com. The SSHFP resource records should first be added to the zonefile for host.example.com: $ ssh-keygen -r host.example.com. The output lines will have to be added to the zonefile. To check that the zone is answering fingerprint queries: $ dig -t SSHFP host.example.com Finally the client connects: $ ssh -o "VerifyHostKeyDNS ask" host.example.com [...] Matching host key fingerprint found in DNS. Are you sure you want to continue connecting (yes/no)? See the VerifyHostKeyDNS option in ssh_config(5) for more information. SSH-BASED VIRTUAL PRIVATE NETWORKS top contains support for Virtual Private Network (VPN) tunnelling using the tun(4) network pseudo-device, allowing two networks to be joined securely. The sshd_config(5) configuration option PermitTunnel controls whether the server supports this, and at what level (layer 2 or 3 traffic). The following example would connect client network 10.0.50.0/24 with remote network 10.0.99.0/24 using a point-to-point connection from 10.1.1.1 to 10.1.1.2, provided that the SSH server running on the gateway to the remote network, at 192.168.1.15, allows it. On the client: # ssh -f -w 0:1 192.168.1.15 true # ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252 # route add 10.0.99.0/24 10.1.1.2 On the server: # ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252 # route add 10.0.50.0/24 10.1.1.1 Client access may be more finely tuned via the /root/.ssh/authorized_keys file (see below) and the PermitRootLogin server option. The following entry would permit connections on tun(4) device 1 from user jane and on tun device 2 from user john, if PermitRootLogin is set to forced-commands-only: tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john Since an SSH-based setup entails a fair amount of overhead, it may be more suited to temporary setups, such as for wireless VPNs. More permanent VPNs are better provided by tools such as ipsecctl(8) and isakmpd(8). ENVIRONMENT top will normally set the following environment variables: DISPLAY The DISPLAY variable indicates the location of the X11 server. It is automatically set by to point to a value of the form hostname:n, where hostname indicates the host where the shell runs, and n is an integer 1. uses this special value to forward X11 connections over the secure channel. The user should normally not set DISPLAY explicitly, as that will render the X11 connection insecure (and will require the user to manually copy any required authorization cookies). HOME Set to the path of the user's home directory. LOGNAME Synonym for USER; set for compatibility with systems that use this variable. MAIL Set to the path of the user's mailbox. PATH Set to the default PATH, as specified when compiling . SSH_ASKPASS If needs a passphrase, it will read the passphrase from the current terminal if it was run from a terminal. If does not have a terminal associated with it but DISPLAY and SSH_ASKPASS are set, it will execute the program specified by SSH_ASKPASS and open an X11 window to read the passphrase. This is particularly useful when calling from a .xsession or related script. (Note that on some machines it may be necessary to redirect the input from /dev/null to make this work.) SSH_ASKPASS_REQUIRE Allows further control over the use of an askpass program. If this variable is set to never then will never attempt to use one. If it is set to prefer, then will prefer to use the askpass program instead of the TTY when requesting passwords. Finally, if the variable is set to force, then the askpass program will be used for all passphrase input regardless of whether DISPLAY is set. SSH_AUTH_SOCK Identifies the path of a Unix-domain socket used to communicate with the agent. SSH_CONNECTION Identifies the client and server ends of the connection. The variable contains four space-separated values: client IP address, client port number, server IP address, and server port number. SSH_ORIGINAL_COMMAND This variable contains the original command line if a forced command is executed. It can be used to extract the original arguments. SSH_TTY This is set to the name of the tty (path to the device) associated with the current shell or command. If the current session has no tty, this variable is not set. SSH_TUNNEL Optionally set by sshd(8) to contain the interface names assigned if tunnel forwarding was requested by the client. SSH_USER_AUTH Optionally set by sshd(8), this variable may contain a pathname to a file that lists the authentication methods successfully used when the session was established, including any public keys that were used. TZ This variable is set to indicate the present time zone if it was set when the daemon was started (i.e. the daemon passes the value on to new connections). USER Set to the name of the user logging in. Additionally, reads ~/.ssh/environment, and adds lines of the format VARNAME=value to the environment if the file exists and users are allowed to change their environment. For more information, see the PermitUserEnvironment option in sshd_config(5). FILES top ~/.rhosts This file is used for host-based authentication (see above). On some machines this file may need to be world- readable if the user's home directory is on an NFS partition, because sshd(8) reads it as root. Additionally, this file must be owned by the user, and must not have write permissions for anyone else. The recommended permission for most machines is read/write for the user, and not accessible by others. ~/.shosts This file is used in exactly the same way as .rhosts, but allows host-based authentication without permitting login with rlogin/rsh. ~/.ssh/ This directory is the default location for all user- specific configuration and authentication information. There is no general requirement to keep the entire contents of this directory secret, but the recommended permissions are read/write/execute for the user, and not accessible by others. ~/.ssh/authorized_keys Lists the public keys (DSA, ECDSA, Ed25519, RSA) that can be used for logging in as this user. The format of this file is described in the sshd(8) manual page. This file is not highly sensitive, but the recommended permissions are read/write for the user, and not accessible by others. ~/.ssh/config This is the per-user configuration file. The file format and configuration options are described in ssh_config(5). Because of the potential for abuse, this file must have strict permissions: read/write for the user, and not writable by others. ~/.ssh/environment Contains additional definitions for environment variables; see ENVIRONMENT, above. ~/.ssh/id_dsa ~/.ssh/id_ecdsa ~/.ssh/id_ecdsa_sk ~/.ssh/id_ed25519 ~/.ssh/id_ed25519_sk ~/.ssh/id_rsa Contains the private key for authentication. These files contain sensitive data and should be readable by the user but not accessible by others (read/write/execute). will simply ignore a private key file if it is accessible by others. It is possible to specify a passphrase when generating the key which will be used to encrypt the sensitive part of this file using AES-128. ~/.ssh/id_dsa.pub ~/.ssh/id_ecdsa.pub ~/.ssh/id_ecdsa_sk.pub ~/.ssh/id_ed25519.pub ~/.ssh/id_ed25519_sk.pub ~/.ssh/id_rsa.pub Contains the public key for authentication. These files are not sensitive and can (but need not) be readable by anyone. ~/.ssh/known_hosts Contains a list of host keys for all hosts the user has logged into that are not already in the systemwide list of known host keys. See sshd(8) for further details of the format of this file. ~/.ssh/rc Commands in this file are executed by when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information. /etc/hosts.equiv This file is for host-based authentication (see above). It should only be writable by root. /etc/shosts.equiv This file is used in exactly the same way as hosts.equiv, but allows host-based authentication without permitting login with rlogin/rsh. /etc/ssh/ssh_config Systemwide configuration file. The file format and configuration options are described in ssh_config(5). /etc/ssh/ssh_host_key /etc/ssh/ssh_host_dsa_key /etc/ssh/ssh_host_ecdsa_key /etc/ssh/ssh_host_ed25519_key /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys and are used for host-based authentication. /etc/ssh/ssh_known_hosts Systemwide list of known host keys. This file should be prepared by the system administrator to contain the public host keys of all machines in the organization. It should be world-readable. See sshd(8) for further details of the format of this file. /etc/ssh/sshrc Commands in this file are executed by when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information. EXIT STATUS top exits with the exit status of the remote command or with 255 if an error occurred. SEE ALSO top scp(1), sftp(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), ssh-keyscan(1), tun(4), ssh_config(5), ssh-keysign(8), sshd(8) STANDARDS top S. Lehtinen and C. Lonvick, The Secure Shell (SSH) Protocol Assigned Numbers, RFC 4250, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Protocol Architecture, RFC 4251, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Authentication Protocol, RFC 4252, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Transport Layer Protocol, RFC 4253, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Connection Protocol, RFC 4254, January 2006. J. Schlyter and W. Griffin, Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints, RFC 4255, January 2006. F. Cusack and M. Forssen, Generic Message Exchange Authentication for the Secure Shell Protocol (SSH), RFC 4256, January 2006. J. Galbraith and P. Remaker, The Secure Shell (SSH) Session Channel Break Extension, RFC 4335, January 2006. M. Bellare, T. Kohno, and C. Namprempre, The Secure Shell (SSH) Transport Layer Encryption Modes, RFC 4344, January 2006. B. Harris, Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol, RFC 4345, January 2006. M. Friedl, N. Provos, and W. Simpson, Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol, RFC 4419, March 2006. J. Galbraith and R. Thayer, The Secure Shell (SSH) Public Key File Format, RFC 4716, November 2006. D. Stebila and J. Green, Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer, RFC 5656, December 2009. A. Perrig and D. Song, Hash Visualization: a New Technique to improve Real-World Security, 1999, International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99). AUTHORS top OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re- added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. COLOPHON top This page is part of the openssh (Portable OpenSSH) project. Information about the project can be found at http://www.openssh.com/portable.html. If you have a bug report for this manual page, see http://www.openssh.com/report.html. This page was obtained from the tarball openssh-9.6p1.tar.gz fetched from http://ftp.eu.openbsd.org/pub/OpenBSD/OpenSSH/portable/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU October 11, 2023 SSH(1) Pages that refer to this page: stap-jupyter(1), systemd-stdio-bridge(1), tar(1), sd_bus_default(3), environment.d(5), proc(5), user@.service(5), pty(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check that the master ssh connection "officefirewall" is running Bash Command:<START>ssh -O check officefirewall<END>

Check the environment variables generated by switching to the root account.

sudo env

['env', 'sudo']

Output a Bash command to accomplish the following task. Task: Check the environment variables generated by switching to the root account. Bash Command:<START>sudo env<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # env\n\n> Show the environment or run a program in a modified environment.\n> More information: <https://www.gnu.org/software/coreutils/env>.\n\n- Show the environment:\n\n`env`\n\n- Run a program. Often used in scripts after the shebang (#!) for looking up the path to the program:\n\n`env {{program}}`\n\n- Clear the environment and run a program:\n\n`env -i {{program}}`\n\n- Remove variable from the environment and run a program:\n\n`env -u {{variable}} {{program}}`\n\n- Set a variable and run a program:\n\n`env {{variable}}={{value}} {{program}}`\n\n- Set one or more variables and run a program:\n\n`env {{variable1}}={{value}} {{variable2}}={{value}} {{variable3}}={{value}} {{program}}`\n # sudo\n\n> Executes a single command as the superuser or another user.\n> More information: <https://www.sudo.ws/sudo.html>.\n\n- Run a command as the superuser:\n\n`sudo {{less /var/log/syslog}}`\n\n- Edit a file as the superuser with your default editor:\n\n`sudo --edit {{/etc/fstab}}`\n\n- Run a command as another user and/or group:\n\n`sudo --user={{user}} --group={{group}} {{id -a}}`\n\n- Repeat the last command prefixed with `sudo` (only in Bash, Zsh, etc.):\n\n`sudo !!`\n\n- Launch the default shell with superuser privileges and run login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login`\n\n- Launch the default shell with superuser privileges without changing the environment:\n\n`sudo --shell`\n\n- Launch the default shell as the specified user, loading the user's environment and reading login-specific files (`.profile`, `.bash_profile`, etc.):\n\n`sudo --login --user={{user}}`\n\n- List the allowed (and forbidden) commands for the invoking user:\n\n`sudo --list`\n Task: Check the environment variables generated by switching to the root account. Bash Command:<START>sudo env<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: env(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training env(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NOTES | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON ENV(1) User Commands ENV(1) NAME top env - run a program in a modified environment SYNOPSIS top env [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...] DESCRIPTION top Set each NAME to VALUE in the environment and run COMMAND. Mandatory arguments to long options are mandatory for short options too. -i, --ignore-environment start with an empty environment -0, --null end each output line with NUL, not newline -u, --unset=NAME remove variable from the environment -C, --chdir=DIR change working directory to DIR -S, --split-string=S process and split S into separate arguments; used to pass multiple arguments on shebang lines --block-signal[=SIG] block delivery of SIG signal(s) to COMMAND --default-signal[=SIG] reset handling of SIG signal(s) to the default --ignore-signal[=SIG] set handling of SIG signal(s) to do nothing --list-signal-handling list non default signal handling to stderr -v, --debug print verbose information for each processing step --help display this help and exit --version output version information and exit A mere - implies -i. If no COMMAND, print the resulting environment. SIG may be a signal name like 'PIPE', or a signal number like '13'. Without SIG, all known signals are included. Multiple signals can be comma-separated. An empty SIG argument is a no-op. Exit status: 125 if the env command itself fails 126 if COMMAND is found but cannot be invoked 127 if COMMAND cannot be found - the exit status of COMMAND otherwise OPTIONS top -S/--split-string usage in scripts The -S option allows specifying multiple parameters in a script. Running a script named 1.pl containing the following first line: #!/usr/bin/env -S perl -w -T ... Will execute perl -w -T 1.pl . Without the '-S' parameter the script will likely fail with: /usr/bin/env: 'perl -w -T': No such file or directory See the full documentation for more details. --default-signal[=SIG] usage This option allows setting a signal handler to its default action, which is not possible using the traditional shell trap command. The following example ensures that seq will be terminated by SIGPIPE no matter how this signal is being handled in the process invoking the command. sh -c 'env --default-signal=PIPE seq inf | head -n1' NOTES top POSIX's exec(3p) pages says: "many existing applications wrongly assume that they start with certain signals set to the default action and/or unblocked.... Therefore, it is best not to block or ignore signals across execs without explicit reason to do so, and especially not to block signals across execs of arbitrary (not closely cooperating) programs." AUTHOR top Written by Richard Mlynarik, David MacKenzie, and Assaf Gordon. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top sigaction(2), sigprocmask(2), signal(7) Full documentation <https://www.gnu.org/software/coreutils/env> or available locally via: info '(coreutils) env invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 ENV(1) Pages that refer to this page: pmpython(1), environ(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. sudo(8) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sudo(8) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND EXECUTION | EXIT VALUE | SECURITY NOTES | ENVIRONMENT | FILES | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | AUTHORS | CAVEATS | BUGS | SUPPORT | DISCLAIMER | COLOPHON SUDO(8) System Manager's Manual SUDO(8) NAME top sudo, sudoedit execute a command as another user SYNOPSIS top sudo -h | -K | -k | -V sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command [arg ...]] sudo [-ABbEHnPS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] [VAR=value] [-i | -s] [command [arg ...]] sudoedit [-ABkNnS] [-C num] [-D directory] [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] [-u user] file ... DESCRIPTION top allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user-ID is used to determine the user name with which to query the security policy. supports a plugin architecture for security policies, auditing, and input/output logging. Third parties can develop and distribute their own plugins to work seamlessly with the front- end. The default security policy is sudoers, which is configured via the file /etc/sudoers, or via LDAP. See the Plugins section for more information. The security policy determines what privileges, if any, a user has to run . The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific; the default password prompt timeout for the sudoers security policy is 5 minutes. Security policies may support credential caching to allow the user to run again for a period of time without requiring authentication. By default, the sudoers policy caches credentials on a per-terminal basis for 5 minutes. See the timestamp_type and timestamp_timeout options in sudoers(5) for more information. By running with the -v option, a user can update the cached credentials without running a command. On systems where is the primary method of gaining superuser privileges, it is imperative to avoid syntax errors in the security policy configuration files. For the default security policy, sudoers(5), changes to the configuration files should be made using the visudo(8) utility which will ensure that no syntax errors are introduced. When invoked as sudoedit, the -e option (described below), is implied. Security policies and audit plugins may log successful and failed attempts to run . If an I/O plugin is configured, the running command's input and output may be logged as well. The options are as follows: -A, --askpass Normally, if requires a password, it will read it from the user's terminal. If the -A (askpass) option is specified, a (possibly graphical) helper program is executed to read the user's password and output the password to the standard output. If the SUDO_ASKPASS environment variable is set, it specifies the path to the helper program. Otherwise, if sudo.conf(5) contains a line specifying the askpass program, that value will be used. For example: # Path to askpass helper program Path askpass /usr/X11R6/bin/ssh-askpass If no askpass program is available, will exit with an error. -B, --bell Ring the bell as part of the password prompt when a terminal is present. This option has no effect if an askpass program is used. -b, --background Run the given command in the background. It is not possible to use shell job control to manipulate background processes started by . Most interactive commands will fail to work properly in background mode. -C num, --close-from=num Close all file descriptors greater than or equal to num before executing a command. Values less than three are not permitted. By default, will close all open file descriptors other than standard input, standard output, and standard error when executing a command. The security policy may restrict the user's ability to use this option. The sudoers policy only permits use of the -C option when the administrator has enabled the closefrom_override option. -D directory, --chdir=directory Run the command in the specified directory instead of the current working directory. The security policy may return an error if the user does not have permission to specify the working directory. -E, --preserve-env Indicates to the security policy that the user wishes to preserve their existing environment variables. The security policy may return an error if the user does not have permission to preserve the environment. --preserve-env=list Indicates to the security policy that the user wishes to add the comma-separated list of environment variables to those preserved from the user's environment. The security policy may return an error if the user does not have permission to preserve the environment. This option may be specified multiple times. -e, --edit Edit one or more files instead of running a command. In lieu of a path name, the string "sudoedit" is used when consulting the security policy. If the user is authorized by the policy, the following steps are taken: 1. Temporary copies are made of the files to be edited with the owner set to the invoking user. 2. The editor specified by the policy is run to edit the temporary files. The sudoers policy uses the SUDO_EDITOR, VISUAL and EDITOR environment variables (in that order). If none of SUDO_EDITOR, VISUAL or EDITOR are set, the first program listed in the editor sudoers(5) option is used. 3. If they have been modified, the temporary files are copied back to their original location and the temporary versions are removed. To help prevent the editing of unauthorized files, the following restrictions are enforced unless explicitly allowed by the security policy: Symbolic links may not be edited (version 1.8.15 and higher). Symbolic links along the path to be edited are not followed when the parent directory is writable by the invoking user unless that user is root (version 1.8.16 and higher). Files located in a directory that is writable by the invoking user may not be edited unless that user is root (version 1.8.16 and higher). Users are never allowed to edit device special files. If the specified file does not exist, it will be created. Unlike most commands run by sudo, the editor is run with the invoking user's environment unmodified. If the temporary file becomes empty after editing, the user will be prompted before it is installed. If, for some reason, is unable to update a file with its edited version, the user will receive a warning and the edited copy will remain in a temporary file. -g group, --group=group Run the command with the primary group set to group instead of the primary group specified by the target user's password database entry. The group may be either a group name or a numeric group-ID (GID) prefixed with the # character (e.g., #0 for GID 0). When running a command as a GID, many shells require that the # be escaped with a backslash (\). If no -u option is specified, the command will be run as the invoking user. In either case, the primary group will be set to group. The sudoers policy permits any of the target user's groups to be specified via the -g option as long as the -P option is not in use. -H, --set-home Request that the security policy set the HOME environment variable to the home directory specified by the target user's password database entry. Depending on the policy, this may be the default behavior. -h, --help Display a short help message to the standard output and exit. -h host, --host=host Run the command on the specified host if the security policy plugin supports remote commands. The sudoers plugin does not currently support running remote commands. This may also be used in conjunction with the -l option to list a user's privileges for the remote host. -i, --login Run the shell specified by the target user's password database entry as a login shell. This means that login- specific resource files such as .profile, .bash_profile, or .login will be read by the shell. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. attempts to change to that user's home directory before running the shell. The command is run with an environment similar to the one a user would receive at log in. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. The Command environment section in the sudoers(5) manual documents how the -i option affects the environment in which a command is run when the sudoers policy is in use. -K, --remove-timestamp Similar to the -k option, except that it removes every cached credential for the user, regardless of the terminal or parent process ID. The next time is run, a password must be entered if the security policy requires authentication. It is not possible to use the -K option in conjunction with a command or other option. This option does not require a password. Not all security policies support credential caching. -k, --reset-timestamp When used without a command, invalidates the user's cached credentials for the current session. The next time is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with commands run in a different terminal session. See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke permissions from a .logout file. When used in conjunction with a command or an option that may require a password, this option will cause to ignore the user's cached credentials. As a result, will prompt for a password (if one is required by the security policy) and will not update the user's cached credentials. Not all security policies support credential caching. -l, --list If no command is specified, list the privileges for the invoking user (or the user specified by the -U option) on the current host. A longer list format is used if this option is specified multiple times and the security policy supports a verbose output format. If a command is specified and is permitted by the security policy for the invoking user (or the, user specified by the -U option) on the current host, the fully-qualified path to the command is displayed along with any args. If -l is specified more than once (and the security policy supports it), the matching rule is displayed in a verbose format along with the command. If a command is specified but not allowed by the policy, will exit with a status value of 1. -N, --no-update Do not update the user's cached credentials, even if the user successfully authenticates. Unlike the -k flag, existing cached credentials are used if they are valid. To detect when the user's cached credentials are valid (or when no authentication is required), the following can be used: sudo -Nnv Not all security policies support credential caching. -n, --non-interactive Avoid prompting the user for input of any kind. If a password is required for the command to run, will display an error message and exit. -P, --preserve-groups Preserve the invoking user's group vector unaltered. By default, the sudoers policy will initialize the group vector to the list of groups the target user is a member of. The real and effective group-IDs, however, are still set to match the target user. -p prompt, --prompt=prompt Use a custom password prompt with optional escape sequences. The following percent (%) escape sequences are supported by the sudoers policy: %H expanded to the host name including the domain name (only if the machine's host name is fully qualified or the fqdn option is set in sudoers(5)) %h expanded to the local host name without the domain name %p expanded to the name of the user whose password is being requested (respects the rootpw, targetpw, and runaspw flags in sudoers(5)) %U expanded to the login name of the user the command will be run as (defaults to root unless the -u option is also specified) %u expanded to the invoking user's login name %% two consecutive % characters are collapsed into a single % character The custom prompt will override the default prompt specified by either the security policy or the SUDO_PROMPT environment variable. On systems that use PAM, the custom prompt will also override the prompt specified by a PAM module unless the passprompt_override flag is disabled in sudoers. -R directory, --chroot=directory Change to the specified root directory (see chroot(8)) before running the command. The security policy may return an error if the user does not have permission to specify the root directory. -S, --stdin Write the prompt to the standard error and read the password from the standard input instead of using the terminal device. -s, --shell Run the shell specified by the SHELL environment variable if it is set or the shell specified by the invoking user's password database entry. If a command is specified, it is passed to the shell as a simple command using the -c option. The command and any args are concatenated, separated by spaces, after escaping each character (including white space) with a backslash (\) except for alphanumerics, underscores, hyphens, and dollar signs. If no command is specified, an interactive shell is executed. Most shells behave differently when a command is specified as compared to an interactive session; consult the shell's manual for details. -U user, --other-user=user Used in conjunction with the -l option to list the privileges for user instead of for the invoking user. The security policy may restrict listing other users' privileges. When using the sudoers policy, the -U option is restricted to the root user and users with either the list priviege for the specified user or the ability to run any command as root or user on the current host. -T timeout, --command-timeout=timeout Used to set a timeout for the command. If the timeout expires before the command has exited, the command will be terminated. The security policy may restrict the user's ability to set timeouts. The sudoers policy requires that user-specified timeouts be explicitly enabled. -u user, --user=user Run the command as a user other than the default target user (usually root). The user may be either a user name or a numeric user-ID (UID) prefixed with the # character (e.g., #0 for UID 0). When running commands as a UID, many shells require that the # be escaped with a backslash (\). Some security policies may restrict UIDs to those listed in the password database. The sudoers policy allows UIDs that are not in the password database as long as the targetpw option is not set. Other security policies may not support this. -V, --version Print the version string as well as the version string of any configured plugins. If the invoking user is already root, the -V option will display the options passed to configure when was built; plugins may display additional information such as default options. -v, --validate Update the user's cached credentials, authenticating the user if necessary. For the sudoers plugin, this extends the timeout for another 5 minutes by default, but does not run a command. Not all security policies support cached credentials. -- The -- is used to delimit the end of the options. Subsequent options are passed to the command. Options that take a value may only be specified once unless otherwise indicated in the description. This is to help guard against problems caused by poorly written scripts that invoke sudo with user-controlled input. Environment variables to be set for the command may also be passed as options to in the form VAR=value, for example LD_LIBRARY_PATH=/usr/local/pkg/lib. Environment variables may be subject to restrictions imposed by the security policy plugin. The sudoers policy subjects environment variables passed as options to the same restrictions as existing environment variables with one important difference. If the setenv option is set in sudoers, the command to be run has the SETENV tag set or the command matched is ALL, the user may set variables that would otherwise be forbidden. See sudoers(5) for more information. COMMAND EXECUTION top When executes a command, the security policy specifies the execution environment for the command. Typically, the real and effective user and group and IDs are set to match those of the target user, as specified in the password database, and the group vector is initialized based on the group database (unless the -P option was specified). The following parameters may be specified by security policy: real and effective user-ID real and effective group-ID supplementary group-IDs the environment list current working directory file creation mode mask (umask) scheduling priority (aka nice value) Process model There are two distinct ways can run a command. If an I/O logging plugin is configured to log terminal I/O, or if the security policy explicitly requests it, a new pseudo-terminal (pty) is allocated and fork(2) is used to create a second process, referred to as the monitor. The monitor creates a new terminal session with itself as the leader and the pty as its controlling terminal, calls fork(2) again, sets up the execution environment as described above, and then uses the execve(2) system call to run the command in the child process. The monitor exists to relay job control signals between the user's terminal and the pty the command is being run in. This makes it possible to suspend and resume the command normally. Without the monitor, the command would be in what POSIX terms an orphaned process group and it would not receive any job control signals from the kernel. When the command exits or is terminated by a signal, the monitor passes the command's exit status to the main process and exits. After receiving the command's exit status, the main process passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugin, and exits. This mode is the default for sudo versions 1.9.14 and above when using the sudoers policy. If no pty is used, calls fork(2), sets up the execution environment as described above, and uses the execve(2) system call to run the command in the child process. The main process waits until the command has completed, then passes the command's exit status to the security policy's close function, as well as the close function of any configured audit plugins, and exits. As a special case, if the policy plugin does not define a close function, will execute the command directly instead of calling fork(2) first. The sudoers policy plugin will only define a close function when I/O logging is enabled, a pty is required, an SELinux role is specified, the command has an associated timeout, or the pam_session or pam_setcred options are enabled. Both pam_session and pam_setcred are enabled by default on systems using PAM. This mode is the default for sudo versions prior to 1.9.14 when using the sudoers policy. On systems that use PAM, the security policy's close function is responsible for closing the PAM session. It may also log the command's exit status. Signal handling When the command is run as a child of the process, will relay signals it receives to the command. The SIGINT and SIGQUIT signals are only relayed when the command is being run in a new pty or when the signal was sent by a user process, not the kernel. This prevents the command from receiving SIGINT twice each time the user enters control-C. Some signals, such as SIGSTOP and SIGKILL, cannot be caught and thus will not be relayed to the command. As a general rule, SIGTSTP should be used instead of SIGSTOP when you wish to suspend a command being run by . As a special case, will not relay signals that were sent by the command it is running. This prevents the command from accidentally killing itself. On some systems, the reboot(8) utility sends SIGTERM to all non-system processes other than itself before rebooting the system. This prevents from relaying the SIGTERM signal it received back to reboot(8), which might then exit before the system was actually rebooted, leaving it in a half-dead state similar to single user mode. Note, however, that this check only applies to the command run by and not any other processes that the command may create. As a result, running a script that calls reboot(8) or shutdown(8) via may cause the system to end up in this undefined state unless the reboot(8) or shutdown(8) are run using the exec() family of functions instead of system() (which interposes a shell between the command and the calling process). Plugins Plugins may be specified via Plugin directives in the sudo.conf(5) file. They may be loaded as dynamic shared objects (on systems that support them), or compiled directly into the binary. If no sudo.conf(5) file is present, or if it doesn't contain any Plugin lines, will use sudoers(5) for the policy, auditing, and I/O logging plugins. See the sudo.conf(5) manual for details of the /etc/sudo.conf file and the sudo_plugin(5) manual for more information about the plugin architecture. EXIT VALUE top Upon successful execution of a command, the exit status from will be the exit status of the program that was executed. If the command terminated due to receipt of a signal, will send itself the same signal that terminated the command. If the -l option was specified without a command, will exit with a value of 0 if the user is allowed to run and they authenticated successfully (as required by the security policy). If a command is specified with the -l option, the exit value will only be 0 if the command is permitted by the security policy, otherwise it will be 1. If there is an authentication failure, a configuration/permission problem, or if the given command cannot be executed, exits with a value of 1. In the latter case, the error string is printed to the standard error. If cannot stat(2) one or more entries in the user's PATH, an error is printed to the standard error. (If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed.) This should not happen under normal circumstances. The most common reason for stat(2) to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. SECURITY NOTES top tries to be safe when executing external commands. To prevent command spoofing, checks "." and "" (both denoting current directory) last when searching for a command in the user's PATH (if one or both are in the PATH). Depending on the security policy, the user's PATH environment variable may be modified, replaced, or passed unchanged to the program that executes. Users should never be granted privileges to execute files that are writable by the user or that reside in a directory that is writable by the user. If the user can modify or replace the command there is no way to limit what additional commands they can run. By default, will only log the command it explicitly runs. If a user runs a command such as sudo su or sudo sh, subsequent commands run from that shell are not subject to sudo's security policy. The same is true for commands that offer shell escapes (including most editors). If I/O logging is enabled, subsequent commands will have their input and/or output logged, but there will not be traditional logs for those commands. Because of this, care must be taken when giving users access to commands via to verify that the command does not inadvertently give the user an effective root shell. For information on ways to address this, see the Preventing shell escapes section in sudoers(5). To prevent the disclosure of potentially sensitive information, disables core dumps by default while it is executing (they are re-enabled for the command that is run). This historical practice dates from a time when most operating systems allowed set-user-ID processes to dump core by default. To aid in debugging crashes, you may wish to re-enable core dumps by setting disable_coredump to false in the sudo.conf(5) file as follows: Set disable_coredump false See the sudo.conf(5) manual for more information. ENVIRONMENT top utilizes the following environment variables. The security policy has control over the actual content of the command's environment. EDITOR Default editor to use in -e (sudoedit) mode if neither SUDO_EDITOR nor VISUAL is set. MAIL Set to the mail spool of the target user when the -i option is specified, or when env_reset is enabled in sudoers (unless MAIL is present in the env_keep list). HOME Set to the home directory of the target user when the -i or -H options are specified, when the -s option is specified and set_home is set in sudoers, when always_set_home is enabled in sudoers, or when env_reset is enabled in sudoers and HOME is not present in the env_keep list. LOGNAME Set to the login name of the target user when the -i option is specified, when the set_logname option is enabled in sudoers, or when the env_reset option is enabled in sudoers (unless LOGNAME is present in the env_keep list). PATH May be overridden by the security policy. SHELL Used to determine shell to run with -s option. SUDO_ASKPASS Specifies the path to a helper program used to read the password if no terminal is available or if the -A option is specified. SUDO_COMMAND Set to the command run by sudo, including any args. The args are truncated at 4096 characters to prevent a potential execution error. SUDO_EDITOR Default editor to use in -e (sudoedit) mode. SUDO_GID Set to the group-ID of the user who invoked sudo. SUDO_PROMPT Used as the default password prompt unless the -p option was specified. SUDO_PS1 If set, PS1 will be set to its value for the program being run. SUDO_UID Set to the user-ID of the user who invoked sudo. SUDO_USER Set to the login name of the user who invoked sudo. USER Set to the same value as LOGNAME, described above. VISUAL Default editor to use in -e (sudoedit) mode if SUDO_EDITOR is not set. FILES top /etc/sudo.conf front-end configuration EXAMPLES top The following examples assume a properly configured security policy. To get a file listing of an unreadable directory: $ sudo ls /usr/local/protected To list the home directory of user yaz on a machine where the file system holding ~yaz is not exported as root: $ sudo -u yaz ls ~yaz To edit the index.html file as user www: $ sudoedit -u www ~www/htdocs/index.html To view system logs only accessible to root and users in the adm group: $ sudo -g adm more /var/log/syslog To run an editor as jim with a different primary group: $ sudoedit -u jim -g audio ~jim/sound.txt To shut down a machine: $ sudo shutdown -r +15 "quick reboot" To make a usage listing of the directories in the /home partition. The commands are run in a sub-shell to allow the cd command and file redirection to work. $ sudo sh -c "cd /home ; du -s * | sort -rn > USAGE" DIAGNOSTICS top Error messages produced by include: editing files in a writable directory is not permitted By default, sudoedit does not permit editing a file when any of the parent directories are writable by the invoking user. This avoids a race condition that could allow the user to overwrite an arbitrary file. See the sudoedit_checkdir option in sudoers(5) for more information. editing symbolic links is not permitted By default, sudoedit does not follow symbolic links when opening files. See the sudoedit_follow option in sudoers(5) for more information. effective uid is not 0, is sudo installed setuid root? was not run with root privileges. The binary must be owned by the root user and have the set-user-ID bit set. Also, it must not be located on a file system mounted with the nosuid option or on an NFS file system that maps uid 0 to an unprivileged uid. effective uid is not 0, is sudo on a file system with the 'nosuid' option set or an NFS file system without root privileges? was not run with root privileges. The binary has the proper owner and permissions but it still did not run with root privileges. The most common reason for this is that the file system the binary is located on is mounted with the nosuid option or it is an NFS file system that maps uid 0 to an unprivileged uid. fatal error, unable to load plugins An error occurred while loading or initializing the plugins specified in sudo.conf(5). invalid environment variable name One or more environment variable names specified via the -E option contained an equal sign (=). The arguments to the -E option should be environment variable names without an associated value. no password was provided When tried to read the password, it did not receive any characters. This may happen if no terminal is available (or the -S option is specified) and the standard input has been redirected from /dev/null. a terminal is required to read the password needs to read the password but there is no mechanism available for it to do so. A terminal is not present to read the password from, has not been configured to read from the standard input, the -S option was not used, and no askpass helper has been specified either via the sudo.conf(5) file or the SUDO_ASKPASS environment variable. no writable temporary directory found sudoedit was unable to find a usable temporary directory in which to store its intermediate files. The no new privileges flag is set, which prevents sudo from running as root. was run by a process that has the Linux no new privileges flag is set. This causes the set-user-ID bit to be ignored when running an executable, which will prevent from functioning. The most likely cause for this is running within a container that sets this flag. Check the documentation to see if it is possible to configure the container such that the flag is not set. sudo must be owned by uid 0 and have the setuid bit set was not run with root privileges. The binary does not have the correct owner or permissions. It must be owned by the root user and have the set-user-ID bit set. sudoedit is not supported on this platform It is only possible to run sudoedit on systems that support setting the effective user-ID. timed out reading password The user did not enter a password before the password timeout (5 minutes by default) expired. you do not exist in the passwd database Your user-ID does not appear in the system passwd database. you may not specify environment variables in edit mode It is only possible to specify environment variables when running a command. When editing a file, the editor is run with the user's environment unmodified. SEE ALSO top su(1), stat(2), login_cap(3), passwd(5), sudo.conf(5), sudo_plugin(5), sudoers(5), sudoers_timestamp(5), sudoreplay(8), visudo(8) HISTORY top See the HISTORY.md file in the distribution (https://www.sudo.ws/about/history/) for a brief history of sudo. AUTHORS top Many people have worked on over the years; this version consists of code written primarily by: Todd C. Miller See the CONTRIBUTORS.md file in the distribution (https://www.sudo.ws/about/contributors/) for an exhaustive list of people who have contributed to . CAVEATS top There is no easy way to prevent a user from gaining a root shell if that user is allowed to run arbitrary commands via . Also, many programs (such as editors) allow the user to run commands via shell escapes, thus avoiding sudo's checks. However, on most systems it is possible to prevent shell escapes with the sudoers(5) plugin's noexec functionality. It is not meaningful to run the cd command directly via sudo, e.g., $ sudo cd /usr/local/protected since when the command exits the parent process (your shell) will still be the same. The -D option can be used to run a command in a specific directory. Running shell scripts via can expose the same kernel bugs that make set-user-ID shell scripts unsafe on some operating systems (if your OS has a /dev/fd/ directory, set-user-ID shell scripts are generally safe). BUGS top If you believe you have found a bug in , you can submit a bug report at https://bugzilla.sudo.ws/ SUPPORT top Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives. DISCLAIMER top is provided AS IS and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. See the LICENSE.md file distributed with or https://www.sudo.ws/about/license/ for complete details. COLOPHON top This page is part of the sudo (execute a command as another user) project. Information about the project can be found at https://www.sudo.ws/. If you have a bug report for this manual page, see https://bugzilla.sudo.ws/. This page was obtained from the project's upstream Git repository https://github.com/sudo-project/sudo on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org Sudo 1.9.15p4 August 9, 2023 SUDO(8) Pages that refer to this page: homectl(1), journalctl(1), localectl(1), loginctl(1), machinectl(1), portablectl(1), setpriv(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-ask-password(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), uid0(1), userdbctl(1), nsswitch.conf(5), credentials(7), systemd-tmpfiles(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check the environment variables generated by switching to the root account. Bash Command:<START>sudo env<END>

Check whether "$path_in_question" is a mount point

df $path_in_question | grep " $path_in_question$"

['grep', 'df']

Output a Bash command to accomplish the following task. Task: Check whether "$path_in_question" is a mount point Bash Command:<START>df $path_in_question | grep " $path_in_question$"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # df\n\n> Display an overview of the filesystem disk space usage.\n> More information: <https://www.gnu.org/software/coreutils/df>.\n\n- Display all filesystems and their disk usage:\n\n`df`\n\n- Display all filesystems and their disk usage in human-readable form:\n\n`df -h`\n\n- Display the filesystem and its disk usage containing the given file or directory:\n\n`df {{path/to/file_or_directory}}`\n\n- Include statistics on the number of free inodes:\n\n`df -i`\n\n- Display filesystems but exclude the specified types:\n\n`df -x {{squashfs}} -x {{tmpfs}}`\n Task: Check whether "$path_in_question" is a mount point Bash Command:<START>df $path_in_question | grep " $path_in_question$"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. df(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training df(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DF(1) User Commands DF(1) NAME top df - report file system space usage SYNOPSIS top df [OPTION]... [FILE]... DESCRIPTION top This manual page documents the GNU version of df. df displays the amount of space available on the file system containing each file name argument. If no file name is given, the space available on all currently mounted file systems is shown. Space is shown in 1K blocks by default, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. If an argument is the absolute file name of a device node containing a mounted file system, df shows the space available on that file system rather than on the file system containing the device node. This version of df cannot show the space available on unmounted file systems, because on most kinds of systems doing so requires non-portable intimate knowledge of file system structures. OPTIONS top Show information about the file system on which each FILE resides, or all file systems by default. Mandatory arguments to long options are mandatory for short options too. -a, --all include pseudo, duplicate, inaccessible file systems -B, --block-size=SIZE scale sizes by SIZE before printing them; e.g., '-BM' prints sizes in units of 1,048,576 bytes; see SIZE format below -h, --human-readable print sizes in powers of 1024 (e.g., 1023M) -H, --si print sizes in powers of 1000 (e.g., 1.1G) -i, --inodes list inode information instead of block usage -k like --block-size=1K -l, --local limit listing to local file systems --no-sync do not invoke sync before getting usage info (default) --output[=FIELD_LIST] use the output format defined by FIELD_LIST, or print all fields if FIELD_LIST is omitted. -P, --portability use the POSIX output format --sync invoke sync before getting usage info --total elide all entries insignificant to available space, and produce a grand total -t, --type=TYPE limit listing to file systems of type TYPE -T, --print-type print file system type -x, --exclude-type=TYPE limit listing to file systems not of type TYPE -v (ignored) --help display this help and exit --version output version information and exit Display values are in units of the first available SIZE from --block-size, and the DF_BLOCK_SIZE, BLOCK_SIZE and BLOCKSIZE environment variables. Otherwise, units default to 1024 bytes (or 512 if POSIXLY_CORRECT is set). The SIZE argument is an integer and optional unit (example: 10K is 10*1024). Units are K,M,G,T,P,E,Z,Y,R,Q (powers of 1024) or KB,MB,... (powers of 1000). Binary prefixes can be used, too: KiB=K, MiB=M, and so on. FIELD_LIST is a comma-separated list of columns to be included. Valid field names are: 'source', 'fstype', 'itotal', 'iused', 'iavail', 'ipcent', 'size', 'used', 'avail', 'pcent', 'file' and 'target' (see info page). AUTHOR top Written by Torbjorn Granlund, David MacKenzie, and Paul Eggert. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top Full documentation <https://www.gnu.org/software/coreutils/df> or available locally via: info '(coreutils) df invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DF(1) Pages that refer to this page: fstab(5), tmpfs(5), findmnt(8), xfs_quota(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check whether "$path_in_question" is a mount point Bash Command:<START>df $path_in_question | grep " $path_in_question$"<END>

Check whether "/full/path" is a mount point with no output and using the exit code

df /full/path | grep -q /full/path

['grep', 'df']

Output a Bash command to accomplish the following task. Task: Check whether "/full/path" is a mount point with no output and using the exit code Bash Command:<START>df /full/path | grep -q /full/path<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # df\n\n> Display an overview of the filesystem disk space usage.\n> More information: <https://www.gnu.org/software/coreutils/df>.\n\n- Display all filesystems and their disk usage:\n\n`df`\n\n- Display all filesystems and their disk usage in human-readable form:\n\n`df -h`\n\n- Display the filesystem and its disk usage containing the given file or directory:\n\n`df {{path/to/file_or_directory}}`\n\n- Include statistics on the number of free inodes:\n\n`df -i`\n\n- Display filesystems but exclude the specified types:\n\n`df -x {{squashfs}} -x {{tmpfs}}`\n Task: Check whether "/full/path" is a mount point with no output and using the exit code Bash Command:<START>df /full/path | grep -q /full/path<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. df(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training df(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DF(1) User Commands DF(1) NAME top df - report file system space usage SYNOPSIS top df [OPTION]... [FILE]... DESCRIPTION top This manual page documents the GNU version of df. df displays the amount of space available on the file system containing each file name argument. If no file name is given, the space available on all currently mounted file systems is shown. Space is shown in 1K blocks by default, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. If an argument is the absolute file name of a device node containing a mounted file system, df shows the space available on that file system rather than on the file system containing the device node. This version of df cannot show the space available on unmounted file systems, because on most kinds of systems doing so requires non-portable intimate knowledge of file system structures. OPTIONS top Show information about the file system on which each FILE resides, or all file systems by default. Mandatory arguments to long options are mandatory for short options too. -a, --all include pseudo, duplicate, inaccessible file systems -B, --block-size=SIZE scale sizes by SIZE before printing them; e.g., '-BM' prints sizes in units of 1,048,576 bytes; see SIZE format below -h, --human-readable print sizes in powers of 1024 (e.g., 1023M) -H, --si print sizes in powers of 1000 (e.g., 1.1G) -i, --inodes list inode information instead of block usage -k like --block-size=1K -l, --local limit listing to local file systems --no-sync do not invoke sync before getting usage info (default) --output[=FIELD_LIST] use the output format defined by FIELD_LIST, or print all fields if FIELD_LIST is omitted. -P, --portability use the POSIX output format --sync invoke sync before getting usage info --total elide all entries insignificant to available space, and produce a grand total -t, --type=TYPE limit listing to file systems of type TYPE -T, --print-type print file system type -x, --exclude-type=TYPE limit listing to file systems not of type TYPE -v (ignored) --help display this help and exit --version output version information and exit Display values are in units of the first available SIZE from --block-size, and the DF_BLOCK_SIZE, BLOCK_SIZE and BLOCKSIZE environment variables. Otherwise, units default to 1024 bytes (or 512 if POSIXLY_CORRECT is set). The SIZE argument is an integer and optional unit (example: 10K is 10*1024). Units are K,M,G,T,P,E,Z,Y,R,Q (powers of 1024) or KB,MB,... (powers of 1000). Binary prefixes can be used, too: KiB=K, MiB=M, and so on. FIELD_LIST is a comma-separated list of columns to be included. Valid field names are: 'source', 'fstype', 'itotal', 'iused', 'iavail', 'ipcent', 'size', 'used', 'avail', 'pcent', 'file' and 'target' (see info page). AUTHOR top Written by Torbjorn Granlund, David MacKenzie, and Paul Eggert. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top Full documentation <https://www.gnu.org/software/coreutils/df> or available locally via: info '(coreutils) df invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 DF(1) Pages that refer to this page: fstab(5), tmpfs(5), findmnt(8), xfs_quota(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Check whether "/full/path" is a mount point with no output and using the exit code Bash Command:<START>df /full/path | grep -q /full/path<END>

Checks that 'monit' user is in 'www-data' group.

groups monit |grep www-data

['grep', 'groups']

Output a Bash command to accomplish the following task. Task: Checks that 'monit' user is in 'www-data' group. Bash Command:<START>groups monit |grep www-data<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # groups\n\n> Print group memberships for a user.\n> See also: `groupadd`, `groupdel`, `groupmod`.\n> More information: <https://www.gnu.org/software/coreutils/groups>.\n\n- Print group memberships for the current user:\n\n`groups`\n\n- Print group memberships for a list of users:\n\n`groups {{username1 username2 ...}}`\n Task: Checks that 'monit' user is in 'www-data' group. Bash Command:<START>groups monit |grep www-data<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. groups(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training Another version of this page is provided by the shadow-utils project groups(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON GROUPS(1) User Commands GROUPS(1) NAME top groups - print the groups a user is in SYNOPSIS top groups [OPTION]... [USERNAME]... DESCRIPTION top Print group memberships for each USERNAME or, if no USERNAME is specified, for the current process (which may differ if the groups database has changed). --help display this help and exit --version output version information and exit AUTHOR top Written by David MacKenzie and James Youngman. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top getent(1) Full documentation <https://www.gnu.org/software/coreutils/groups> or available locally via: info '(coreutils) groups invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 GROUPS(1) Pages that refer to this page: group(5), credentials(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Checks that 'monit' user is in 'www-data' group. Bash Command:<START>groups monit |grep www-data<END>

Clean the current directory from all subversion directories recursively

find . -type d -name ".svn" -print | xargs rm -rf

['find', 'xargs', 'rm']

Output a Bash command to accomplish the following task. Task: Clean the current directory from all subversion directories recursively Bash Command:<START>find . -type d -name ".svn" -print | xargs rm -rf<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # xargs\n\n> Execute a command with piped arguments coming from another command, a file, etc.\n> The input is treated as a single block of text and split into separate pieces on spaces, tabs, newlines and end-of-file.\n> More information: <https://pubs.opengroup.org/onlinepubs/9699919799/utilities/xargs.html>.\n\n- Run a command using the input data as arguments:\n\n`{{arguments_source}} | xargs {{command}}`\n\n- Run multiple chained commands on the input data:\n\n`{{arguments_source}} | xargs sh -c "{{command1}} && {{command2}} | {{command3}}"`\n\n- Delete all files with a `.backup` extension (`-print0` uses a null character to split file names, and `-0` uses it as delimiter):\n\n`find . -name {{'*.backup'}} -print0 | xargs -0 rm -v`\n\n- Execute the command once for each input line, replacing any occurrences of the placeholder (here marked as `_`) with the input line:\n\n`{{arguments_source}} | xargs -I _ {{command}} _ {{optional_extra_arguments}}`\n\n- Parallel runs of up to `max-procs` processes at a time; the default is 1. If `max-procs` is 0, xargs will run as many processes as possible at a time:\n\n`{{arguments_source}} | xargs -P {{max-procs}} {{command}}`\n # rm\n\n> Remove files or directories.\n> See also: `rmdir`.\n> More information: <https://www.gnu.org/software/coreutils/rm>.\n\n- Remove specific files:\n\n`rm {{path/to/file1 path/to/file2 ...}}`\n\n- Remove specific files ignoring nonexistent ones:\n\n`rm --force {{path/to/file1 path/to/file2 ...}}`\n\n- Remove specific files interactively prompting before each removal:\n\n`rm --interactive {{path/to/file1 path/to/file2 ...}}`\n\n- Remove specific files printing info about each removal:\n\n`rm --verbose {{path/to/file1 path/to/file2 ...}}`\n\n- Remove specific files and directories recursively:\n\n`rm --recursive {{path/to/file_or_directory1 path/to/file_or_directory2 ...}}`\n Task: Clean the current directory from all subversion directories recursively Bash Command:<START>find . -type d -name ".svn" -print | xargs rm -rf<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. xargs(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training xargs(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | STANDARDS CONFORMANCE | HISTORY | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON XARGS(1) General Commands Manual XARGS(1) NAME top xargs - build and execute command lines from standard input SYNOPSIS top xargs [options] [command [initial-arguments]] DESCRIPTION top This manual page documents the GNU version of xargs. xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is echo) one or more times with any initial-arguments followed by items read from standard input. Blank lines on the standard input are ignored. The command line for command is built up until it reaches a system-defined limit (unless the -n and -L options are used). The specified command will be invoked as many times as necessary to use up the list of input items. In general, there will be many fewer invocations of command than there were items in the input. This will normally have significant performance benefits. Some commands can usefully be executed in parallel too; see the -P option. Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing blanks and/or newlines are incorrectly processed by xargs. In these situations it is better to use the -0 option, which prevents such problems. When using this option you will need to ensure that the program which produces the input for xargs also uses a null character as a separator. If that program is GNU find for example, the -print0 option does this for you. If any invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input. An error message is issued on stderr when this happens. OPTIONS top -0, --null Input items are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character is taken literally). Disables the end-of-file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. The GNU find -print0 option produces input suitable for this mode. -a file, --arg-file=file Read items from file instead of standard input. If you use this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null. --delimiter=delim, -d delim Input items are terminated by the specified character. The specified delimiter may be a single character, a C- style character escape such as \n, or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible. -E eof-str Set the end-of-file string to eof-str. If the end-of-file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end-of-file string is used. -e[eof-str], --eof[=eof-str] This option is a synonym for the -E option. Use -E instead, because it is POSIX compliant while this option is not. If eof-str is omitted, there is no end-of-file string. If neither -E nor -e is used, no end-of-file string is used. -I replace-str Replace occurrences of replace-str in the initial- arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1. -i[replace-str], --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. The -i option is deprecated; use -I instead. -L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x. -l[max-lines], --max-lines[=max-lines] Synonym for the -L option. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one. The -l option is deprecated since the POSIX standard specifies -L instead. -n max-args, --max-args=max-args Use at most max-args arguments per command line. Fewer than max-args arguments will be used if the size (see the -s option) is exceeded, unless the -x option is given, in which case xargs will exit. -P max-procs, --max-procs=max-procs Run up to max-procs processes at a time; the default is 1. If max-procs is 0, xargs will run as many processes as possible at a time. Use the -n option or the -L option with -P; otherwise chances are that only one exec will be done. While xargs is running, you can send its process a SIGUSR1 signal to increase the number of commands to run simultaneously, or a SIGUSR2 to decrease the number. You cannot increase it above an implementation-defined limit (which is shown with --show-limits). You cannot decrease it below 1. xargs never terminates its commands; when asked to decrease, it merely waits for more than one existing command to terminate before starting another. Please note that it is up to the called processes to properly manage parallel access to shared resources. For example, if more than one of them tries to print to stdout, the output will be produced in an indeterminate order (and very likely mixed up) unless the processes collaborate in some way to prevent this. Using some kind of locking scheme is one way to prevent such problems. In general, using a locking scheme will help ensure correct output but reduce performance. If you don't want to tolerate the performance difference, simply arrange for each process to produce a separate output file (or otherwise use separate resources). -o, --open-tty Reopen stdin as /dev/tty in the child process before executing the command. This is useful if you want xargs to run an interactive application. -p, --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with `y' or `Y'. Implies -t. --process-slot-var=name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example. -r, --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension. -s max-chars, --max-chars=max-chars Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends of the argument strings. The largest allowed value is system-dependent, and is calculated as the argument length limit for exec, less the size of your environment, less 2048 bytes of headroom. If this value is more than 128 KiB, 128 KiB is used as the default value; otherwise, the default value is the maximum. 1 KiB is 1024 bytes. xargs automatically adapts to tighter constraints. --show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything. -t, --verbose Print the command line on the standard error output before executing it. -x, --exit Exit if the size (see the -s option) is exceeded. -- Delimit the option list. Later arguments, if any, are treated as operands even if they begin with -. For example, xargs -- --help runs the command --help (found in PATH) instead of printing the usage text, and xargs -- --mycommand runs the command --mycommand instead of rejecting this as unrecognized option. --help Print a summary of the options to xargs and exit. --version Print the version number of xargs and exit. The options --max-lines (-L, -l), --replace (-I, -i) and --max- args (-n) are mutually exclusive. If some of them are specified at the same time, then xargs will generally use the option specified last on the command line, i.e., it will reset the value of the offending option (given before) to its default value. Additionally, xargs will issue a warning diagnostic on stderr. The exception to this rule is that the special max-args value 1 ('-n1') is ignored after the --replace option and its aliases -I and -i, because it would not actually conflict. EXAMPLES top find /tmp -name core -type f -print | xargs /bin/rm -f Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines or spaces. find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing spaces or newlines are correctly handled. find /tmp -depth -name core -type f -delete Find files named core in or below the directory /tmp and delete them, but more efficiently than in the previous example (because we avoid the need to use fork(2) and exec(2) to launch rm and we don't need the extra xargs process). cut -d: -f1 < /etc/passwd | sort | xargs echo Generates a compact listing of all the users on the system. EXIT STATUS top xargs exits with the following status: 0 if it succeeds 123 if any invocation of the command exited with status 1125 124 if the command exited with status 255 125 if the command is killed by a signal 126 if the command cannot be run 127 if the command is not found 1 if some other error occurred. Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal. STANDARDS CONFORMANCE top As of GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows this. The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard. Therefore you should use -L and -I instead, respectively. The -o option is an extension to the POSIX standard for better compatibility with BSD. The POSIX standard allows implementations to have a limit on the size of arguments to the exec functions. This limit could be as low as 4096 bytes including the size of the environment. For scripts to be portable, they must not rely on a larger value. However, I know of no implementation whose actual limit is that small. The --show-limits option can be used to discover the actual limits in force on the current system. HISTORY top The xargs program was invented by Herb Gellis at Bell Labs. See the Texinfo manual for findutils, Finding Files, for more information. BUGS top It is not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and their use in the commands that xargs issues. If other users have access to the system, they can manipulate the filesystem during this time window to force the action of the commands xargs runs to apply to files that you didn't intend. For a more detailed discussion of this and related problems, please refer to the ``Security Considerations'' chapter in the findutils Texinfo documentation. The -execdir option of find can often be used as a more secure alternative. When you use the -I option, each line read from the input is buffered internally. This means that there is an upper limit on the length of input line that xargs will accept when used with the -I option. To work around this limitation, you can use the -s option to increase the amount of buffer space that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur. For example: somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}' Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option. The second invocation of xargs does have such a limit, but we have ensured that it never encounters a line which is longer than it can handle. This is not an ideal solution. Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section. The problem doesn't occur with the output of find(1) because it emits just one filename per line. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 19902023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top find(1), kill(1), locate(1), updatedb(1), fork(2), execvp(3), locatedb(5), signal(7) Full documentation <https://www.gnu.org/software/findutils/xargs> or available locally via: info xargs COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org XARGS(1) Pages that refer to this page: dpkg-name(1), find(1), grep(1), locate(1), updatedb(1), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. rm(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training rm(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON RM(1) User Commands RM(1) NAME top rm - remove files or directories SYNOPSIS top rm [OPTION]... [FILE]... DESCRIPTION top This manual page documents the GNU version of rm. rm removes each specified file. By default, it does not remove directories. If the -I or --interactive=once option is given, and there are more than three files or the -r, -R, or --recursive are given, then rm prompts the user for whether to proceed with the entire operation. If the response is not affirmative, the entire command is aborted. Otherwise, if a file is unwritable, standard input is a terminal, and the -f or --force option is not given, or the -i or --interactive=always option is given, rm prompts the user for whether to remove the file. If the response is not affirmative, the file is skipped. OPTIONS top Remove (unlink) the FILE(s). -f, --force ignore nonexistent files and arguments, never prompt -i prompt before every removal -I prompt once before removing more than three files, or when removing recursively; less intrusive than -i, while still giving protection against most mistakes --interactive[=WHEN] prompt according to WHEN: never, once (-I), or always (-i); without WHEN, prompt always --one-file-system when removing a hierarchy recursively, skip any directory that is on a file system different from that of the corresponding command line argument --no-preserve-root do not treat '/' specially --preserve-root[=all] do not remove '/' (default); with 'all', reject any command line argument on a separate device from its parent -r, -R, --recursive remove directories and their contents recursively -d, --dir remove empty directories -v, --verbose explain what is being done --help display this help and exit --version output version information and exit By default, rm does not remove directories. Use the --recursive (-r or -R) option to remove each listed directory, too, along with all of its contents. To remove a file whose name starts with a '-', for example '-foo', use one of these commands: rm -- -foo rm ./-foo Note that if you use rm to remove a file, it might be possible to recover some of its contents, given sufficient expertise and/or time. For greater assurance that the contents are truly unrecoverable, consider using shred(1). AUTHOR top Written by Paul Rubin, David MacKenzie, Richard M. Stallman, and Jim Meyering. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top unlink(1), unlink(2), chattr(1), shred(1) Full documentation <https://www.gnu.org/software/coreutils/rm> or available locally via: info '(coreutils) rm invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 RM(1) Pages that refer to this page: rmdir(2), unlink(2), remove(3), mq_overview(7), symlink(7), debugfs(8), lsof(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Clean the current directory from all subversion directories recursively Bash Command:<START>find . -type d -name ".svn" -print | xargs rm -rf<END>

Clean up all zombie processes by instantly killing their parent process with SIGKILL signal.

kill -9 $(ps -A -ostat,ppid | grep -e '[zZ]'| awk '{ print $2 }')

['ps', 'awk', 'grep', 'kill']

Output a Bash command to accomplish the following task. Task: Clean up all zombie processes by instantly killing their parent process with SIGKILL signal. Bash Command:<START>kill -9 $(ps -A -ostat,ppid | grep -e '[zZ]'| awk '{ print $2 }')<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # ps\n\n> Information about running processes.\n> More information: <https://manned.org/ps>.\n\n- List all running processes:\n\n`ps aux`\n\n- List all running processes including the full command string:\n\n`ps auxww`\n\n- Search for a process that matches a string:\n\n`ps aux | grep {{string}}`\n\n- List all processes of the current user in extra full format:\n\n`ps --user $(id -u) -F`\n\n- List all processes of the current user as a tree:\n\n`ps --user $(id -u) f`\n\n- Get the parent PID of a process:\n\n`ps -o ppid= -p {{pid}}`\n\n- Sort processes by memory consumption:\n\n`ps --sort size`\n # awk\n\n> A versatile programming language for working on files.\n> More information: <https://github.com/onetrueawk/awk>.\n\n- Print the fifth column (a.k.a. field) in a space-separated file:\n\n`awk '{print $5}' {{path/to/file}}`\n\n- Print the second column of the lines containing "foo" in a space-separated file:\n\n`awk '/{{foo}}/ {print $2}' {{path/to/file}}`\n\n- Print the last column of each line in a file, using a comma (instead of space) as a field separator:\n\n`awk -F ',' '{print $NF}' {{path/to/file}}`\n\n- Sum the values in the first column of a file and print the total:\n\n`awk '{s+=$1} END {print s}' {{path/to/file}}`\n\n- Print every third line starting from the first line:\n\n`awk 'NR%3==1' {{path/to/file}}`\n\n- Print different values based on conditions:\n\n`awk '{if ($1 == "foo") print "Exact match foo"; else if ($1 ~ "bar") print "Partial match bar"; else print "Baz"}' {{path/to/file}}`\n\n- Print all lines where the 10th column value equals the specified value:\n\n`awk '($10 == {{value}})'`\n\n- Print all the lines which the 10th column value is between a min and a max:\n\n`awk '($10 >= {{min_value}} && $10 <= {{max_value}})'`\n # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # kill\n\n> Sends a signal to a process, usually related to stopping the process.\n> All signals except for SIGKILL and SIGSTOP can be intercepted by the process to perform a clean exit.\n> More information: <https://manned.org/kill>.\n\n- Terminate a program using the default SIGTERM (terminate) signal:\n\n`kill {{process_id}}`\n\n- List signal values and their corresponding names (to be used without the `SIG` prefix):\n\n`kill -{{L|-table}}`\n\n- Terminate a background job:\n\n`kill %{{job_id}}`\n\n- Terminate a program using the SIGHUP (hang up) signal. Many daemons will reload instead of terminating:\n\n`kill -{{1|HUP}} {{process_id}}`\n\n- Terminate a program using the SIGINT (interrupt) signal. This is typically initiated by the user pressing `Ctrl + C`:\n\n`kill -{{2|INT}} {{process_id}}`\n\n- Signal the operating system to immediately terminate a program (which gets no chance to capture the signal):\n\n`kill -{{9|KILL}} {{process_id}}`\n\n- Signal the operating system to pause a program until a SIGCONT ("continue") signal is received:\n\n`kill -{{17|STOP}} {{process_id}}`\n\n- Send a `SIGUSR1` signal to all processes with the given GID (group id):\n\n`kill -{{SIGUSR1}} -{{group_id}}`\n Task: Clean up all zombie processes by instantly killing their parent process with SIGKILL signal. Bash Command:<START>kill -9 $(ps -A -ostat,ppid | grep -e '[zZ]'| awk '{ print $2 }')<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: ps(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training ps(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SIMPLE PROCESS SELECTION | PROCESS SELECTION BY LIST | OUTPUT FORMAT CONTROL | OUTPUT MODIFIERS | THREAD DISPLAY | OTHER INFORMATION | NOTES | PROCESS FLAGS | PROCESS STATE CODES | OBSOLETE SORT KEYS | AIX FORMAT DESCRIPTORS | STANDARD FORMAT SPECIFIERS | ENVIRONMENT VARIABLES | PERSONALITY | BUGS | SEE ALSO | STANDARDS | AUTHOR | COLOPHON PS(1) User Commands PS(1) NAME top ps - report a snapshot of the current processes. SYNOPSIS top ps [options] DESCRIPTION top ps displays information about a selection of the active processes. If you want a repetitive update of the selection and the displayed information, use top instead. This version of ps accepts several kinds of options: 1 UNIX options, which may be grouped and must be preceded by a dash. 2 BSD options, which may be grouped and must not be used with a dash. 3 GNU long options, which are preceded by two dashes. Options of different types may be freely mixed, but conflicts can appear. There are some synonymous options, which are functionally identical, due to the many standards and ps implementations that this ps is compatible with. By default, ps selects all processes with the same effective user ID (euid=EUID) as the current user and associated with the same terminal as the invoker. It displays the process ID (pid=PID), the terminal associated with the process (tname=TTY), the cumulated CPU time in [DD-]hh:mm:ss format (time=TIME), and the executable name (ucmd=CMD). Output is unsorted by default. The use of BSD-style options will add process state (stat=STAT) to the default display and show the command args (args=COMMAND) instead of the executable name. You can override this with the PS_FORMAT environment variable. The use of BSD-style options will also change the process selection to include processes on other terminals (TTYs) that are owned by you; alternately, this may be described as setting the selection to be the set of all processes filtered to exclude processes owned by other users or not on a terminal. These effects are not considered when options are described as being "identical" below, so -M will be considered identical to Z and so on. Except as described below, process selection options are additive. The default selection is discarded, and then the selected processes are added to the set of processes to be displayed. A process will thus be shown if it meets any of the given selection criteria. EXAMPLES top To see every process on the system using standard syntax: ps -e ps -ef ps -eF ps -ely To see every process on the system using BSD syntax: ps ax ps axu To print a process tree: ps -ejH ps axjf To get info about threads: ps -eLf ps axms To get security info: ps -eo euser,ruser,suser,fuser,f,comm,label ps axZ ps -eM To see every process running as root (real & effective ID) in user format: ps -U root -u root u To see every process with a user-defined format: ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm ps -Ao pid,tt,user,fname,tmout,f,wchan Print only the process IDs of syslogd: ps -C syslogd -o pid= Print only the name of PID 42: ps -q 42 -o comm= SIMPLE PROCESS SELECTION top a Lift the BSD-style "only yourself" restriction, which is imposed upon the set of all processes when some BSD-style (without "-") options are used or when the ps personality setting is BSD-like. The set of processes selected in this manner is in addition to the set of processes selected by other means. An alternate description is that this option causes ps to list all processes with a terminal (tty), or to list all processes when used together with the x option. -A Select all processes. Identical to -e. -a Select all processes except both session leaders (see getsid(2)) and processes not associated with a terminal. -d Select all processes except session leaders. --deselect Select all processes except those that fulfill the specified conditions (negates the selection). Identical to -N. -e Select all processes. Identical to -A. g Really all, even session leaders. This flag is obsolete and may be discontinued in a future release. It is normally implied by the a flag, and is only useful when operating in the sunos4 personality. -N Select all processes except those that fulfill the specified conditions (negates the selection). Identical to --deselect. T Select all processes associated with this terminal. Identical to the t option without any argument. r Restrict the selection to only running processes. x Lift the BSD-style "must have a tty" restriction, which is imposed upon the set of all processes when some BSD-style (without "-") options are used or when the ps personality setting is BSD-like. The set of processes selected in this manner is in addition to the set of processes selected by other means. An alternate description is that this option causes ps to list all processes owned by you (same EUID as ps), or to list all processes when used together with the a option. PROCESS SELECTION BY LIST top These options accept a single argument in the form of a blank-separated or comma-separated list. They can be used multiple times. For example: ps -p "1 2" -p 3,4 123 Identical to --pid 123. +123 Identical to --sid 123. -123 Select by process group ID (PGID). -C cmdlist Select by command name. This selects the processes whose executable name is given in cmdlist. NOTE: The command name is not the same as the command line. Previous versions of procps and the kernel truncated this command name to 15 characters. This limitation is no longer present in both. If you depended on matching only 15 characters, you may no longer get a match. -G grplist Select by real group ID (RGID) or name. This selects the processes whose real group name or ID is in the grplist list. The real group ID identifies the group of the user who created the process, see getgid(2). -g grplist Select by session OR by effective group name. Selection by session is specified by many standards, but selection by effective group is the logical behavior that several other operating systems use. This ps will select by session when the list is completely numeric (as sessions are). Group ID numbers will work only when some group names are also specified. See the -s and --group options. --Group grplist Select by real group ID (RGID) or name. Identical to -G. --group grplist Select by effective group ID (EGID) or name. This selects the processes whose effective group name or ID is in grplist. The effective group ID describes the group whose file access permissions are used by the process (see getegid(2)). The -g option is often an alternative to --group. p pidlist Select by process ID. Identical to -p and --pid. -p pidlist Select by PID. This selects the processes whose process ID numbers appear in pidlist. Identical to p and --pid. --pid pidlist Select by process ID. Identical to -p and p. --ppid pidlist Select by parent process ID. This selects the processes with a parent process ID in pidlist. That is, it selects processes that are children of those listed in pidlist. q pidlist Select by process ID (quick mode). Identical to -q and --quick-pid. -q pidlist Select by PID (quick mode). This selects the processes whose process ID numbers appear in pidlist. With this option ps reads the necessary info only for the pids listed in the pidlist and doesn't apply additional filtering rules. The order of pids is unsorted and preserved. No additional selection options, sorting and forest type listings are allowed in this mode. Identical to q and --quick-pid. --quick-pid pidlist Select by process ID (quick mode). Identical to -q and q. -s sesslist Select by session ID. This selects the processes with a session ID specified in sesslist. --sid sesslist Select by session ID. Identical to -s. t ttylist Select by tty. Nearly identical to -t and --tty, but can also be used with an empty ttylist to indicate the terminal associated with ps. Using the T option is considered cleaner than using t with an empty ttylist. -t ttylist Select by tty. This selects the processes associated with the terminals given in ttylist. Terminals (ttys, or screens for text output) can be specified in several forms: /dev/ttyS1, ttyS1, S1. A plain "-" may be used to select processes not attached to any terminal. --tty ttylist Select by terminal. Identical to -t and t. U userlist Select by effective user ID (EUID) or name. This selects the processes whose effective user name or ID is in userlist. The effective user ID describes the user whose file access permissions are used by the process (see geteuid(2)). Identical to -u and --user. -U userlist Select by real user ID (RUID) or name. It selects the processes whose real user name or ID is in the userlist list. The real user ID identifies the user who created the process, see getuid(2). -u userlist Select by effective user ID (EUID) or name. This selects the processes whose effective user name or ID is in userlist. The effective user ID describes the user whose file access permissions are used by the process (see geteuid(2)). Identical to U and --user. --User userlist Select by real user ID (RUID) or name. Identical to -U. --user userlist Select by effective user ID (EUID) or name. Identical to -u and U. OUTPUT FORMAT CONTROL top These options are used to choose the information displayed by ps. The output may differ by personality. -c Show different scheduler information for the -l option. --context Display security context format (for SELinux). -f Do full-format listing. This option can be combined with many other UNIX-style options to add additional columns. It also causes the command arguments to be printed. When used with -L, the NLWP (number of threads) and LWP (thread ID) columns will be added. See the c option, the format keyword args, and the format keyword comm. -F Extra full format. See the -f option, which -F implies. --format format user-defined format. Identical to -o and o. j BSD job control format. -j Jobs format. l Display BSD long format. -l Long format. The -y option is often useful with this. -M Add a column of security data. Identical to Z (for SELinux). O format is preloaded o (overloaded). The BSD O option can act like -O (user-defined output format with some common fields predefined) or can be used to specify sort order. Heuristics are used to determine the behavior of this option. To ensure that the desired behavior is obtained (sorting or formatting), specify the option in some other way (e.g. with -O or --sort). When used as a formatting option, it is identical to -O, with the BSD personality. -O format Like -o, but preloaded with some default columns. Identical to -o pid,format,state,tname,time,command or -o pid,format,tname,time,cmd, see -o below. o format Specify user-defined format. Identical to -o and --format. -o format User-defined format. format is a single argument in the form of a blank-separated or comma-separated list, which offers a way to specify individual output columns. The recognized keywords are described in the STANDARD FORMAT SPECIFIERS section below. Headers may be renamed (ps -o pid,ruser=RealUser -o comm=Command) as desired. If all column headers are empty (ps -o pid= -o comm=) then the header line will not be output. Column width will increase as needed for wide headers; this may be used to widen up columns such as WCHAN (ps -o pid,wchan=WIDE- WCHAN-COLUMN -o comm). Explicit width control (ps opid, wchan:42,cmd) is offered too. The behavior of ps -o pid=X,comm=Y varies with personality; output may be one column named "X,comm=Y" or two columns named "X" and "Y". Use multiple -o options when in doubt. Use the PS_FORMAT environment variable to specify a default as desired; DefSysV and DefBSD are macros that may be used to choose the default UNIX or BSD columns. -P Add a column showing psr. s Display signal format. u Display user-oriented format. v Display virtual memory format. X Register format. -y Do not show flags; show rss in place of addr. This option can only be used with -l. Z Add a column of security data. Identical to -M (for SELinux). OUTPUT MODIFIERS top c Show the true command name. This is derived from the name of the executable file, rather than from the argv value. Command arguments and any modifications to them are thus not shown. This option effectively turns the args format keyword into the comm format keyword; it is useful with the -f format option and with the various BSD-style format options, which all normally display the command arguments. See the -f option, the format keyword args, and the format keyword comm. --cols n Set screen width. --columns n Set screen width. --cumulative Include some dead child process data (as a sum with the parent). -D format Set the date format of the lstart field to format. This format is parsed by strftime(3) and should be a maximum of 24 characters to not mis-align columns. --date-format format Identical to -D. e Show the environment after the command. f ASCII art process hierarchy (forest). --forest ASCII art process tree. h No header. (or, one header per screen in the BSD personality). The h option is problematic. Standard BSD ps uses this option to print a header on each page of output, but older Linux ps uses this option to totally disable the header. This version of ps follows the Linux usage of not printing the header unless the BSD personality has been selected, in which case it prints a header on each page of output. Regardless of the current personality, you can use the long options --headers and --no-headers to enable printing headers each page or disable headers entirely, respectively. -H Show process hierarchy (forest). --headers Repeat header lines, one per page of output. k spec Specify sorting order. Sorting syntax is [+|-]key[,[+|-]key[,...]]. Choose a multi-letter key from the STANDARD FORMAT SPECIFIERS section. The "+" is optional since default direction is increasing numerical or lexicographic order. Identical to --sort. Examples: ps jaxkuid,-ppid,+pid ps axk comm o comm,args ps kstart_time -ef --lines n Set screen height. n Numeric output for WCHAN and USER (including all types of UID and GID). --no-headers Print no header line at all. --no-heading is an alias for this option. O order Sorting order (overloaded). The BSD O option can act like -O (user-defined output format with some common fields predefined) or can be used to specify sort order. Heuristics are used to determine the behavior of this option. To ensure that the desired behavior is obtained (sorting or formatting), specify the option in some other way (e.g. with -O or --sort). For sorting, obsolete BSD O option syntax is O[+|-]k1[,[+|-]k2[,...]]. It orders the processes listing according to the multilevel sort specified by the sequence of one-letter short keys k1,k2, ... described in the OBSOLETE SORT KEYS section below. The "+" is currently optional, merely re-iterating the default direction on a key, but may help to distinguish an O sort from an O format. The "-" reverses direction only on the key it precedes. --rows n Set screen height. S Sum up some information, such as CPU usage, from dead child processes into their parent. This is useful for examining a system where a parent process repeatedly forks off short-lived children to do work. --sort spec Specify sorting order. Sorting syntax is [+|-]key[,[+|-]key[,...]]. Choose a multi-letter key from the STANDARD FORMAT SPECIFIERS section. The "+" is optional since default direction is increasing numerical or lexicographic order. Identical to k. For example: ps jax --sort=uid,-ppid,+pid --signames Show signal masks using abbreviated signal names and expands the collumn. If the column width cannot show all signals, the column will end with a plus "+". Columns with only a hyphen have no signals. w Wide output. Use this option twice for unlimited width. -w Wide output. Use this option twice for unlimited width. --width n Set screen width. THREAD DISPLAY top H Show threads as if they were processes. -L Show threads, possibly with LWP and NLWP columns. m Show threads after processes. -m Show threads after processes. -T Show threads, possibly with SPID column. OTHER INFORMATION top --help section Print a help message. The section argument can be one of simple, list, output, threads, misc, or all. The argument can be shortened to one of the underlined letters as in: s|l|o|t|m|a. --info Print debugging info. L List all format specifiers. V Print the procps-ng version. -V Print the procps-ng version. --version Print the procps-ng version. NOTES top This ps works by reading the virtual files in /proc. This ps does not need to be setuid kmem or have any privileges to run. Do not give this ps any special permissions. CPU usage is currently expressed as the percentage of time spent running during the entire lifetime of a process. This is not ideal, and it does not conform to the standards that ps otherwise conforms to. CPU usage is unlikely to add up to exactly 100%. The SIZE and RSS fields don't count some parts of a process including the page tables, kernel stack, struct thread_info, and struct task_struct. This is usually at least 20 KiB of memory that is always resident. SIZE is the virtual size of the process (code+data+stack). Processes marked <defunct> are dead processes (so-called "zombies") that remain because their parent has not destroyed them properly. These processes will be destroyed by init(8) if the parent process exits. If the length of the username is greater than the width of the display column, the username will be truncated. See the -o and -O formatting options to customize length. Commands options such as ps -aux are not recommended as it is a confusion of two different standards. According to the POSIX and UNIX standards, the above command asks to display all processes with a TTY (generally the commands users are running) plus all processes owned by a user named x. If that user doesn't exist, then ps will assume you really meant "ps aux". PROCESS FLAGS top The sum of these values is displayed in the "F" column, which is provided by the flags output specifier: 1 forked but didn't exec 4 used super-user privileges PROCESS STATE CODES top Here are the different values that the s, stat and state output specifiers (header "STAT" or "S") will display to describe the state of a process: D uninterruptible sleep (usually IO) I Idle kernel thread R running or runnable (on run queue) S interruptible sleep (waiting for an event to complete) T stopped by job control signal t stopped by debugger during the tracing W paging (not valid since the 2.6.xx kernel) X dead (should never be seen) Z defunct ("zombie") process, terminated but not reaped by its parent For BSD formats and when the stat keyword is used, additional characters may be displayed: < high-priority (not nice to other users) N low-priority (nice to other users) L has pages locked into memory (for real-time and custom IO) s is a session leader l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do) + is in the foreground process group OBSOLETE SORT KEYS top These keys are used by the BSD O option (when it is used for sorting). The GNU --sort option doesn't use these keys, but the specifiers described below in the STANDARD FORMAT SPECIFIERS section. Note that the values used in sorting are the internal values ps uses and not the "cooked" values used in some of the output format fields (e.g. sorting on tty will sort into device number, not according to the terminal name displayed). Pipe ps output into the sort(1) command if you want to sort the cooked values. KEY LONG DESCRIPTION c cmd simple name of executable C pcpu cpu utilization f flags flags as in long format F field g pgrp process group ID G tpgid controlling tty process group ID j cutime cumulative user time J cstime cumulative system time k utime user time m min_flt number of minor page faults M maj_flt number of major page faults n cmin_flt cumulative minor page faults N cmaj_flt cumulative major page faults o session session ID p pid process ID P ppid parent process ID r rss resident set size R resident resident pages s size memory size in kilobytes S share amount of shared pages t tty the device number of the controlling tty T start_time time process was started U uid user ID number u user user name v vsize total VM size in KiB y priority kernel scheduling priority AIX FORMAT DESCRIPTORS top This ps supports AIX format descriptors, which work somewhat like the formatting codes of printf(1) and printf(3). The NORMAL codes are described in the next section. CODE NORMAL HEADER %C pcpu %CPU %G group GROUP %P ppid PPID %U user USER %a args COMMAND %c comm COMMAND %g rgroup RGROUP %n nice NI %p pid PID %r pgid PGID %t etime ELAPSED %u ruser RUSER %x time TIME %y tty TTY %z vsz VSZ STANDARD FORMAT SPECIFIERS top Here are the different keywords that may be used to control the output format (e.g., with option -o) or to sort the selected processes with the GNU-style --sort option. For example: ps -eo pid,user,args --sort user This version of ps tries to recognize most of the keywords used in other implementations of ps. The following user-defined format specifiers may contain spaces: args, cmd, comm, command, fname, ucmd, ucomm, lstart, bsdstart, start. Some keywords may not be available for sorting. CODE HEADER DESCRIPTION %cpu %CPU cpu utilization of the process in "##.#" format. Currently, it is the CPU time used divided by the time the process has been running (cputime/realtime ratio), expressed as a percentage. It will not add up to 100% unless you are lucky. (alias pcpu). %mem %MEM ratio of the process's resident set size to the physical memory on the machine, expressed as a percentage. (alias pmem). ag_id AGID The autogroup identifier associated with a process which operates in conjunction with the CFS scheduler to improve interactive desktop performance. ag_nice AGNI The autogroup nice value which affects scheduling of all processes in that group. args COMMAND command with all its arguments as a string. Modifications to the arguments may be shown. The output in this column may contain spaces. A process marked <defunct> is partly dead, waiting to be fully destroyed by its parent. Sometimes the process args will be unavailable; when this happens, ps will instead print the executable name in brackets. (alias cmd, command). See also the comm format keyword, the -f option, and the c option. When specified last, this column will extend to the edge of the display. If ps can not determine display width, as when output is redirected (piped) into a file or another command, the output width is undefined (it may be 80, unlimited, determined by the TERM variable, and so on). The COLUMNS environment variable or --cols option may be used to exactly determine the width in this case. The w or -w option may be also be used to adjust width. blocked BLOCKED mask of the blocked signals, see signal(7). According to the width of the field, a 32 or 64-bit mask in hexadecimal format is displayed, unless the --signames option is used. (alias sig_block, sigmask). bsdstart START time the command started. If the process was started less than 24 hours ago, the output format is " HH:MM", else it is " Mmm:SS" (where Mmm is the three letters of the month). See also lstart, start, start_time, and stime. bsdtime TIME accumulated cpu time, user + system. The display format is usually "MMM:SS", but can be shifted to the right if the process used more than 999 minutes of cpu time. c C processor utilization. Currently, this is the integer value of the percent usage over the lifetime of the process. (see %cpu). caught CAUGHT mask of the caught signals, see signal(7). According to the width of the field, a 32 or 64 bits mask in hexadecimal format is displayed, unless the --signames option is used. (alias sig_catch, sigcatch). cgname CGNAME display name of control groups to which the process belongs. cgroup CGROUP display control groups to which the process belongs. cgroupns CGROUPNSUnique inode number describing the namespace the process belongs to. See namespaces(7). class CLS scheduling class of the process. (alias policy, cls). Field's possible values are: - not reported TS SCHED_OTHER FF SCHED_FIFO RR SCHED_RR B SCHED_BATCH ISO SCHED_ISO IDL SCHED_IDLE DLN SCHED_DEADLINE ? unknown value cls CLS scheduling class of the process. (alias policy, cls). Field's possible values are: - not reported TS SCHED_OTHER FF SCHED_FIFO RR SCHED_RR B SCHED_BATCH ISO SCHED_ISO IDL SCHED_IDLE DLN SCHED_DEADLINE ? unknown value cmd CMD see args. (alias args, command). comm COMMAND command name (only the executable name). The output in this column may contain spaces. (alias ucmd, ucomm). See also the args format keyword, the -f option, and the c option. When specified last, this column will extend to the edge of the display. If ps can not determine display width, as when output is redirected (piped) into a file or another command, the output width is undefined (it may be 80, unlimited, determined by the TERM variable, and so on). The COLUMNS environment variable or --cols option may be used to exactly determine the width in this case. The w or -w option may be also be used to adjust width. command COMMAND See args. (alias args, command). cp CP per-mill (tenths of a percent) CPU usage. (see %cpu). cputime TIME cumulative CPU time, "[DD-]hh:mm:ss" format. (alias time). cputimes TIME cumulative CPU time in seconds (alias times). cuc %CUC The CPU utilization of a process, including dead children, in an extended "##.###" format. (see also %cpu, c, cp, cuu, pcpu). cuu %CUU The CPU utilization of a process in an extended "##.###" format. (see also %cpu, c, cp, cuc, pcpu). drs DRS data resident set size, the amount of private memory reserved by a process. It is also known as DATA. Such memory may not yet be mapped to rss but will always be included included in the vsz amount. egid EGID effective group ID number of the process as a decimal integer. (alias gid). egroup EGROUP effective group ID of the process. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. (alias group). eip EIP instruction pointer. As of kernel 4.9.xx will be zeroed out unless task is exiting or being core dumped. esp ESP stack pointer. As of kernel 4.9.xx will be zeroed out unless task is exiting or being core dumped. etime ELAPSED elapsed time since the process was started, in the form [[DD-]hh:]mm:ss. etimes ELAPSED elapsed time since the process was started, in seconds. environ ENVIRON T{ environment variables for the process. T} euid EUID effective user ID (alias uid). euser EUSER effective user name. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. The n option can be used to force the decimal representation. (alias uname, user). exe EXE path to the executable. Useful if path cannot be printed via cmd, comm or args format options. f F flags associated with the process, see the PROCESS FLAGS section. (alias flag, flags). fgid FGID filesystem access group ID. (alias fsgid). fgroup FGROUP filesystem access group ID. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. (alias fsgroup). flag F see f. (alias f, flags). flags F see f. (alias f, flag). fname COMMAND first 8 bytes of the base name of the process's executable file. The output in this column may contain spaces. fuid FUID filesystem access user ID. (alias fsuid). fuser FUSER filesystem access user ID. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. gid GID see egid. (alias egid). group GROUP see egroup. (alias egroup). ignored IGNORED mask of the ignored signals, see signal(7). According to the width of the field, a 32 or 64 bits mask in hexadecimal format is displayed, unless the --signames option is used. (alias sig_ignore, sigignore). ipcns IPCNS Unique inode number describing the namespace the process belongs to. See namespaces(7). label LABEL security label, most commonly used for SELinux context data. This is for the Mandatory Access Control ("MAC") found on high-security systems. lstart STARTED time the command started. This will be in the form "DDD mmm HH:MM:SS YYY" unless changed by the -D option. lsession SESSION displays the login session identifier of a process, if systemd support has been included. luid LUID displays Login ID associated with a process. lwp LWP light weight process (thread) ID of the dispatchable entity (alias spid, tid). See tid for additional information. lxc LXC The name of the lxc container within which a task is running. If a process is not running inside a container, a dash ('-') will be shown. machine MACHINE displays the machine name for processes assigned to VM or container, if systemd support has been included. maj_flt MAJFLT The number of major page faults that have occurred with this process. min_flt MINFLT The number of minor page faults that have occurred with this process. mntns MNTNS Unique inode number describing the namespace the process belongs to. See namespaces(7). netns NETNS Unique inode number describing the namespace the process belongs to. See namespaces(7). ni NI nice value. This ranges from 19 (nicest) to -20 (not nice to others), see nice(1). (alias nice). nice NI see ni.(alias ni). nlwp NLWP number of lwps (threads) in the process. (alias thcount). numa NUMA The node associated with the most recently used processor. A -1 means that NUMA information is unavailable. nwchan WCHAN address of the kernel function where the process is sleeping (use wchan if you want the kernel function name). oom OOM Out of Memory Score. The value, ranging from 0 to +1000, used to select task(s) to kill when memory is exhausted. oomadj OOMADJ Out of Memory Adjustment Factor. The value is added to the current out of memory score which is then used to determine which task to kill when memory is exhausted. ouid OWNER displays the Unix user identifier of the owner of the session of a process, if systemd support has been included. pcpu %CPU see %cpu. (alias %cpu). pending PENDING mask of the pending signals. See signal(7). Signals pending on the process are distinct from signals pending on individual threads. Use the m option or the -m option to see both. According to the width of the field, a 32 or 64 bits mask in hexadecimal format is displayed, unless the --signames option is used. (alias sig). pgid PGID process group ID or, equivalently, the process ID of the process group leader. (alias pgrp). pgrp PGRP see pgid. (alias pgid). pid PID a number representing the process ID (alias tgid). pidns PIDNS Unique inode number describing the namespace the process belongs to. See namespaces(7). pmem %MEM see %mem. (alias %mem). policy POL scheduling class of the process. (alias class, cls). Possible values are: - not reported TS SCHED_OTHER FF SCHED_FIFO RR SCHED_RR B SCHED_BATCH ISO SCHED_ISO IDL SCHED_IDLE DLN SCHED_DEADLINE ? unknown value ppid PPID parent process ID. pri PRI priority of the process. Higher number means higher priority. psr PSR processor that process last executed on. pss PSS Proportional share size, the non-swapped physical memory, with shared memory proportionally accounted to all tasks mapping it. rbytes RBYTES Number of bytes which this process really did cause to be fetched from the storage layer. rchars RCHARS Number of bytes which this task has caused to be read from storage. rgid RGID real group ID. rgroup RGROUP real group name. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. rops ROPS Number of read I/O operationsthat is, system calls such as read(2) and pread(2). rss RSS resident set size, the non-swapped physical memory that a task has used (in kilobytes). (alias rssize, rsz). rssize RSS see rss. (alias rss, rsz). rsz RSZ see rss. (alias rss, rssize). rtprio RTPRIO realtime priority. ruid RUID real user ID. ruser RUSER real user ID. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. s S minimal state display (one character). See section PROCESS STATE CODES for the different values. See also stat if you want additional information displayed. (alias state). sched SCH scheduling policy of the process. The policies SCHED_OTHER (SCHED_NORMAL), SCHED_FIFO, SCHED_RR, SCHED_BATCH, SCHED_ISO, SCHED_IDLE and SCHED_DEADLINE are respectively displayed as 0, 1, 2, 3, 4, 5 and 6. seat SEAT displays the identifier associated with all hardware devices assigned to a specific workplace, if systemd support has been included. sess SESS session ID or, equivalently, the process ID of the session leader. (alias session, sid). sgi_p P processor that the process is currently executing on. Displays "*" if the process is not currently running or runnable. sgid SGID saved group ID. (alias svgid). sgroup SGROUP saved group name. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. sid SID see sess. (alias sess, session). sig PENDING see pending. (alias pending, sig_pend). sigcatch CAUGHT see caught. (alias caught, sig_catch). sigignore IGNORED see ignored. (alias ignored, sig_ignore). sigmask BLOCKED see blocked. (alias blocked, sig_block). size SIZE approximate amount of swap space that would be required if the process were to dirty all writable pages and then be swapped out. This number is very rough! slice SLICE displays the slice unit which a process belongs to, if systemd support has been included. spid SPID see lwp. (alias lwp, tid). stackp STACKP address of the bottom (start) of stack for the process. start STARTED time the command started. If the process was started less than 24 hours ago, the output format is "HH:MM:SS", else it is " Mmm dd" (where Mmm is a three-letter month name). See also bsdstart, start, start_time, and stime. start_time START starting time or date of the process. Only the year will be displayed if the process was not started the same year ps was invoked, or "MmmDD" if it was not started the same day, or "HH:MM" otherwise. See also bsdstart, start, lstart, and stime. stat STAT multi-character process state. See section PROCESS STATE CODES for the different values meaning. See also s and state if you just want the first character displayed. state S see s. (alias s). stime STIME see start_time. (alias start_time). suid SUID saved user ID. (alias svuid). supgid SUPGID group ids of supplementary groups, if any. See getgroups(2). supgrp SUPGRP group names of supplementary groups, if any. See getgroups(2). suser SUSER saved user name. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. (alias svuser). svgid SVGID see sgid. (alias sgid). svuid SVUID see suid. (alias suid). sz SZ size in physical pages of the core image of the process. This includes text, data, and stack space. Device mappings are currently excluded; this is subject to change. See vsz and rss. tgid TGID a number representing the thread group to which a task belongs (alias pid). It is the process ID of the thread group leader. thcount THCNT see nlwp. (alias nlwp). number of kernel threads owned by the process. tid TID the unique number representing a dispatchable entity (alias spid, tid). This value may also appear as: a process ID (pid); a process group ID (pgrp); a session ID for the session leader (sid); a thread group ID for the thread group leader (tgid); and a tty process group ID for the process group leader (tpgid). time TIME cumulative CPU time, "[DD-]HH:MM:SS" format. (alias cputime). timens TIMENS Unique inode number describing the namespace the process belongs to. See namespaces(7). times TIME cumulative CPU time in seconds (alias cputimes). tname TTY controlling tty (terminal). (alias tt, tty). tpgid TPGID ID of the foreground process group on the tty (terminal) that the process is connected to, or -1 if the process is not connected to a tty. trs TRS text resident set size, the amount of physical memory devoted to executable code. tt TT controlling tty (terminal). (alias tname, tty). tty TT controlling tty (terminal). (alias tname, tt). ucmd CMD see comm. (alias comm, ucomm). ucomm COMMAND see comm. (alias comm, ucmd). uid UID see euid. (alias euid). uname USER see euser. (alias euser, user). unit UNIT displays unit which a process belongs to, if systemd support has been included. user USER see euser. (alias euser, uname). userns USERNS Unique inode number describing the namespace the process belongs to. See namespaces(7). uss USS Unique set size, the non-swapped physical memory, which is not shared with an another task. utsns UTSNS Unique inode number describing the namespace the process belongs to. See namespaces(7). uunit UUNIT displays user unit which a process belongs to, if systemd support has been included. vsize VSZ see vsz. (alias vsz). vsz VSZ virtual memory size of the process in KiB (1024-byte units). Device mappings are currently excluded; this is subject to change. (alias vsize). wbytes WBYTES Number of bytes which this process caused to be sent to the storage layer. wcbytes WCBYTES Number of cancelled write bytes. wchan WCHAN name of the kernel function in which the process is sleeping. wchars WCHARS Number of bytes which this task has caused, or shall cause to be written to disk. wops WOPS Number of write I/O operationsthat is, system calls such as write(2) and pwrite(2). ENVIRONMENT VARIABLES top The following environment variables could affect ps: COLUMNS Override default display width. LINES Override default display height. PS_PERSONALITY Set to one of posix, old, linux, bsd, sun, digital... (see section PERSONALITY below). CMD_ENV Set to one of posix, old, linux, bsd, sun, digital... (see section PERSONALITY below). I_WANT_A_BROKEN_PS Force obsolete command line interpretation. LC_TIME Date format. LIBPROC_HIDE_KERNEL Set this to any value to hide kernel threads normally displayed with the -e option. This is equivalent to selecting --ppid 2 -p 2 --deselect instead. Also works in BSD mode. PS_COLORS Not currently supported. PS_FORMAT Default output format override. You may set this to a format string of the type used for the -o option. The DefSysV and DefBSD values are particularly useful. POSIXLY_CORRECT Don't find excuses to ignore bad "features". POSIX2 When set to "on", acts as POSIXLY_CORRECT. UNIX95 Don't find excuses to ignore bad "features". _XPG Cancel CMD_ENV=irix non-standard behavior. In general, it is a bad idea to set these variables. The one exception is CMD_ENV or PS_PERSONALITY, which could be set to Linux for normal systems. Without that setting, ps follows the useless and bad parts of the Unix98 standard. PERSONALITY top 390 like the OS/390 OpenEdition ps aix like AIX ps bsd like FreeBSD ps (totally non-standard) compaq like Digital Unix ps debian like the old Debian ps digital like Tru64 (was Digital Unix, was OSF/1) ps gnu like the old Debian ps hp like HP-UX ps hpux like HP-UX ps irix like Irix ps linux ***** recommended ***** old like the original Linux ps (totally non-standard) os390 like OS/390 Open Edition ps posix standard s390 like OS/390 Open Edition ps sco like SCO ps sgi like Irix ps solaris2 like Solaris 2+ (SunOS 5) ps sunos4 like SunOS 4 (Solaris 1) ps (totally non-standard) svr4 standard sysv standard tru64 like Tru64 (was Digital Unix, was OSF/1) ps unix standard unix95 standard unix98 standard BUGS top The fields bsdstart and start will only show the abbreviated month name in English. The fields lstart and stime will show the abbreviated month name in the configured locale but may exceed the column width due to the different lengths for abbreviated month and day names across languages. SEE ALSO top pgrep(1), pstree(1), top(1), strftime(3), proc(5). STANDARDS top This ps conforms to: 1 Version 2 of the Single Unix Specification 2 The Open Group Technical Standard Base Specifications, Issue 6 3 IEEE Std 1003.1, 2004 Edition 4 X/Open System Interfaces Extension [UP XSI] 5 ISO/IEC 9945:2003 AUTHOR top ps was originally written by Branko Lankester lankeste@fwi.uva. nl. Michael K. Johnson johnsonm@redhat.com re-wrote it significantly to use the proc filesystem, changing a few things in the process. Michael Shields mjshield@nyx.cs.du.edu added the pid-list feature. Charles Blake cblake@bbn.com added multi-level sorting, the dirent-style library, the device name-to-number mmaped database, the approximate binary search directly on System.map, and many code and documentation cleanups. David Mossberger-Tang wrote the generic BFD support for psupdate. Albert Cahalan albert@users.sf.net rewrote ps for full Unix98 and BSD support, along with some ugly hacks for obsolete and foreign syntax. Please send bug reports to procps@freelists.org. No subscription is required or suggested. COLOPHON top This page is part of the procps-ng (/proc filesystem utilities) project. Information about the project can be found at https://gitlab.com/procps-ng/procps. If you have a bug report for this manual page, see https://gitlab.com/procps-ng/procps/blob/master/Documentation/bugs.md. This page was obtained from the project's upstream Git repository https://gitlab.com/procps-ng/procps.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-10-16.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org procps-ng 2023-10-04 PS(1) Pages that refer to this page: free(1), fuser(1), htop(1), killall(1), pcp-ps(1), pgrep(1), pidstat(1), pmap(1), pmsleep(1), pslog(1), pstree(1), pwdx(1), slabtop(1), systemd(1), systemd-cgls(1), systemd-firstboot(1), systemd-nspawn(1), tcpdump(1), tload(1), top(1), uptime(1), w(1), proc(5), credentials(7), pid_namespaces(7), pthreads(7), sched(7), lsof(8), systemd-machined.service(8), tcpdump(8), vmstat(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. awk(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training awk(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT AWK(1P) POSIX Programmer's Manual AWK(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top awk pattern scanning and processing language SYNOPSIS top awk [-F sepstring] [-v assignment]... program [argument...] awk [-F sepstring] -f progfile [-f progfile]... [-v assignment]... [argument...] DESCRIPTION top The awk utility shall execute programs written in the awk programming language, which is specialized for textual data manipulation. An awk program is a sequence of patterns and corresponding actions. When input is read that matches a pattern, the action associated with that pattern is carried out. Input shall be interpreted as a sequence of records. By default, a record is a line, less its terminating <newline>, but this can be changed by using the RS built-in variable. Each record of input shall be matched in turn against each pattern in the program. For each pattern matched, the associated action shall be executed. The awk utility shall interpret each input record as a sequence of fields where, by default, a field is a string of non-<blank> non-<newline> characters. This default <blank> and <newline> field delimiter can be changed by using the FS built-in variable or the -F sepstring option. The awk utility shall denote the first field in a record $1, the second $2, and so on. The symbol $0 shall refer to the entire record; setting any other field causes the re-evaluation of $0. Assigning to $0 shall reset the values of all other fields and the NF built-in variable. OPTIONS top The awk utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported: -F sepstring Define the input field separator. This option shall be equivalent to: -v FS=sepstring except that if -F sepstring and -v FS=sepstring are both used, it is unspecified whether the FS assignment resulting from -F sepstring is processed in command line order or is processed after the last -v FS=sepstring. See the description of the FS built-in variable, and how it is used, in the EXTENDED DESCRIPTION section. -f progfile Specify the pathname of the file progfile containing an awk program. A pathname of '-' shall denote the standard input. If multiple instances of this option are specified, the concatenation of the files specified as progfile in the order specified shall be the awk program. The awk program can alternatively be specified in the command line as a single argument. -v assignment The application shall ensure that the assignment argument is in the same form as an assignment operand. The specified variable assignment shall occur prior to executing the awk program, including the actions associated with BEGIN patterns (if any). Multiple occurrences of this option can be specified. OPERANDS top The following operands shall be supported: program If no -f option is specified, the first operand to awk shall be the text of the awk program. The application shall supply the program operand as a single argument to awk. If the text does not end in a <newline>, awk shall interpret the text as if it did. argument Either of the following two types of argument can be intermixed: file A pathname of a file that contains the input to be read, which is matched against the set of patterns in the program. If no file operands are specified, or if a file operand is '-', the standard input shall be used. assignment An operand that begins with an <underscore> or alphabetic character from the portable character set (see the table in the Base Definitions volume of POSIX.12017, Section 6.1, Portable Character Set), followed by a sequence of underscores, digits, and alphabetics from the portable character set, followed by the '=' character, shall specify a variable assignment rather than a pathname. The characters before the '=' represent the name of an awk variable; if that name is an awk reserved word (see Grammar) the behavior is undefined. The characters following the <equals-sign> shall be interpreted as if they appeared in the awk program preceded and followed by a double-quote ('"') character, as a STRING token (see Grammar), except that if the last character is an unescaped <backslash>, it shall be interpreted as a literal <backslash> rather than as the first character of the sequence "\"". The variable shall be assigned the value of that STRING token and, if appropriate, shall be considered a numeric string (see Expressions in awk), the variable shall also be assigned its numeric value. Each such variable assignment shall occur just prior to the processing of the following file, if any. Thus, an assignment before the first file argument shall be executed after the BEGIN actions (if any), while an assignment after the last file argument shall occur before the END actions (if any). If there are no file arguments, assignments shall be executed before processing the standard input. STDIN top The standard input shall be used only if no file operands are specified, or if a file operand is '-', or if a progfile option- argument is '-'; see the INPUT FILES section. If the awk program contains no actions and no patterns, but is otherwise a valid awk program, standard input and any file operands shall not be read and awk shall exit with a return status of zero. INPUT FILES top Input files to the awk program from any of the following sources shall be text files: * Any file operands or their equivalents, achieved by modifying the awk variables ARGV and ARGC * Standard input in the absence of any file operands * Arguments to the getline function Whether the variable RS is set to a value other than a <newline> or not, for these files, implementations shall support records terminated with the specified separator up to {LINE_MAX} bytes and may support longer records. If -f progfile is specified, the application shall ensure that the files named by each of the progfile option-arguments are text files and their concatenation, in the same order as they appear in the arguments, is an awk program. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of awk: LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE Determine the locale for the behavior of ranges, equivalence classes, and multi-character collating elements within regular expressions and in comparisons of string values. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments and input files), the behavior of character classes within regular expressions, the identification of characters as letters, and the mapping of uppercase and lowercase characters for the toupper and tolower functions. LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. LC_NUMERIC Determine the radix character used when interpreting numeric input, performing conversions between numeric and string values, and formatting numeric output. Regardless of locale, the <period> character (the decimal-point character of the POSIX locale) is the decimal-point character recognized in processing awk programs (including assignments in command line arguments). NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. PATH Determine the search path when looking for commands executed by system(expr), or input and output pipes; see the Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables. In addition, all environment variables shall be visible via the awk variable ENVIRON. ASYNCHRONOUS EVENTS top Default. STDOUT top The nature of the output files depends on the awk program. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top The nature of the output files depends on the awk program. EXTENDED DESCRIPTION top Overall Program Structure An awk program is composed of pairs of the form: pattern { action } Either the pattern or the action (including the enclosing brace characters) can be omitted. A missing pattern shall match any record of input, and a missing action shall be equivalent to: { print } Execution of the awk program shall start by first executing the actions associated with all BEGIN patterns in the order they occur in the program. Then each file operand (or standard input if no files were specified) shall be processed in turn by reading data from the file until a record separator is seen (<newline> by default). Before the first reference to a field in the record is evaluated, the record shall be split into fields, according to the rules in Regular Expressions, using the value of FS that was current at the time the record was read. Each pattern in the program then shall be evaluated in the order of occurrence, and the action associated with each pattern that matches the current record executed. The action for a matching pattern shall be executed before evaluating subsequent patterns. Finally, the actions associated with all END patterns shall be executed in the order they occur in the program. Expressions in awk Expressions describe computations used in patterns and actions. In the following table, valid expression operations are given in groups from highest precedence first to lowest precedence last, with equal-precedence operators grouped between horizontal lines. In expression evaluation, where the grammar is formally ambiguous, higher precedence operators shall be evaluated before lower precedence operators. In this table expr, expr1, expr2, and expr3 represent any expression, while lvalue represents any entity that can be assigned to (that is, on the left side of an assignment operator). The precise syntax of expressions is given in Grammar. Table 4-1: Expressions in Decreasing Precedence in awk Syntax Name Type of Result Associativity ( expr ) Grouping Type of expr N/A $expr Field reference String N/A lvalue ++ Post-increment Numeric N/A lvalue -- Post-decrement Numeric N/A ++ lvalue Pre-increment Numeric N/A -- lvalue Pre-decrement Numeric N/A expr ^ expr Exponentiation Numeric Right ! expr Logical not Numeric N/A + expr Unary plus Numeric N/A - expr Unary minus Numeric N/A expr * expr Multiplication Numeric Left expr / expr Division Numeric Left expr % expr Modulus Numeric Left expr + expr Addition Numeric Left expr - expr Subtraction Numeric Left expr expr String concatenation String Left expr < expr Less than Numeric None expr <= expr Less than or equal to Numeric None expr != expr Not equal to Numeric None expr == expr Equal to Numeric None expr > expr Greater than Numeric None expr >= expr Greater than or equal to Numeric None expr ~ expr ERE match Numeric None expr !~ expr ERE non-match Numeric None expr in array Array membership Numeric Left ( index ) in array Multi-dimension array Numeric Left membership expr && expr Logical AND Numeric Left expr || expr Logical OR Numeric Left expr1 ? expr2 : expr3Conditional expression Type of selectedRight expr2 or expr3 lvalue ^= expr Exponentiation assignmentNumeric Right lvalue %= expr Modulus assignment Numeric Right lvalue *= expr Multiplication assignmentNumeric Right lvalue /= expr Division assignment Numeric Right lvalue += expr Addition assignment Numeric Right lvalue -= expr Subtraction assignment Numeric Right lvalue = expr Assignment Type of expr Right Each expression shall have either a string value, a numeric value, or both. Except as stated for specific contexts, the value of an expression shall be implicitly converted to the type needed for the context in which it is used. A string value shall be converted to a numeric value either by the equivalent of the following calls to functions defined by the ISO C standard: setlocale(LC_NUMERIC, ""); numeric_value = atof(string_value); or by converting the initial portion of the string to type double representation as follows: The input string is decomposed into two parts: an initial, possibly empty, sequence of white-space characters (as specified by isspace()) and a subject sequence interpreted as a floating-point constant. The expected form of the subject sequence is an optional '+' or '-' sign, then a non-empty sequence of digits optionally containing a <period>, then an optional exponent part. An exponent part consists of 'e' or 'E', followed by an optional sign, followed by one or more decimal digits. The sequence starting with the first digit or the <period> (whichever occurs first) is interpreted as a floating constant of the C language, and if neither an exponent part nor a <period> appears, a <period> is assumed to follow the last digit in the string. If the subject sequence begins with a <hyphen-minus>, the value resulting from the conversion is negated. A numeric value that is exactly equal to the value of an integer (see Section 1.1.2, Concepts Derived from the ISO C Standard) shall be converted to a string by the equivalent of a call to the sprintf function (see String Functions) with the string "%d" as the fmt argument and the numeric value being converted as the first and only expr argument. Any other numeric value shall be converted to a string by the equivalent of a call to the sprintf function with the value of the variable CONVFMT as the fmt argument and the numeric value being converted as the first and only expr argument. The result of the conversion is unspecified if the value of CONVFMT is not a floating-point format specification. This volume of POSIX.12017 specifies no explicit conversions between numbers and strings. An application can force an expression to be treated as a number by adding zero to it, or can force it to be treated as a string by concatenating the null string ("") to it. A string value shall be considered a numeric string if it comes from one of the following: 1. Field variables 2. Input from the getline() function 3. FILENAME 4. ARGV array elements 5. ENVIRON array elements 6. Array elements created by the split() function 7. A command line variable assignment 8. Variable assignment from another numeric string variable and an implementation-dependent condition corresponding to either case (a) or (b) below is met. a. After the equivalent of the following calls to functions defined by the ISO C standard, string_value_end would differ from string_value, and any characters before the terminating null character in string_value_end would be <blank> characters: char *string_value_end; setlocale(LC_NUMERIC, ""); numeric_value = strtod (string_value, &string_value_end); b. After all the following conversions have been applied, the resulting string would lexically be recognized as a NUMBER token as described by the lexical conventions in Grammar: -- All leading and trailing <blank> characters are discarded. -- If the first non-<blank> is '+' or '-', it is discarded. -- Each occurrence of the decimal point character from the current locale is changed to a <period>. In case (a) the numeric value of the numeric string shall be the value that would be returned by the strtod() call. In case (b) if the first non-<blank> is '-', the numeric value of the numeric string shall be the negation of the numeric value of the recognized NUMBER token; otherwise, the numeric value of the numeric string shall be the numeric value of the recognized NUMBER token. Whether or not a string is a numeric string shall be relevant only in contexts where that term is used in this section. When an expression is used in a Boolean context, if it has a numeric value, a value of zero shall be treated as false and any other value shall be treated as true. Otherwise, a string value of the null string shall be treated as false and any other value shall be treated as true. A Boolean context shall be one of the following: * The first subexpression of a conditional expression * An expression operated on by logical NOT, logical AND, or logical OR * The second expression of a for statement * The expression of an if statement * The expression of the while clause in either a while or do...while statement * An expression used as a pattern (as in Overall Program Structure) All arithmetic shall follow the semantics of floating-point arithmetic as specified by the ISO C standard (see Section 1.1.2, Concepts Derived from the ISO C Standard). The value of the expression: expr1 ^ expr2 shall be equivalent to the value returned by the ISO C standard function call: pow(expr1, expr2) The expression: lvalue ^= expr shall be equivalent to the ISO C standard expression: lvalue = pow(lvalue, expr) except that lvalue shall be evaluated only once. The value of the expression: expr1 % expr2 shall be equivalent to the value returned by the ISO C standard function call: fmod(expr1, expr2) The expression: lvalue %= expr shall be equivalent to the ISO C standard expression: lvalue = fmod(lvalue, expr) except that lvalue shall be evaluated only once. Variables and fields shall be set by the assignment statement: lvalue = expression and the type of expression shall determine the resulting variable type. The assignment includes the arithmetic assignments ("+=", "-=", "*=", "/=", "%=", "^=", "++", "--") all of which shall produce a numeric result. The left-hand side of an assignment and the target of increment and decrement operators can be one of a variable, an array with index, or a field selector. The awk language supplies arrays that are used for storing numbers or strings. Arrays need not be declared. They shall initially be empty, and their sizes shall change dynamically. The subscripts, or element identifiers, are strings, providing a type of associative array capability. An array name followed by a subscript within square brackets can be used as an lvalue and thus as an expression, as described in the grammar; see Grammar. Unsubscripted array names can be used in only the following contexts: * A parameter in a function definition or function call * The NAME token following any use of the keyword in as specified in the grammar (see Grammar); if the name used in this context is not an array name, the behavior is undefined A valid array index shall consist of one or more <comma>-separated expressions, similar to the way in which multi- dimensional arrays are indexed in some programming languages. Because awk arrays are really one-dimensional, such a <comma>-separated list shall be converted to a single string by concatenating the string values of the separate expressions, each separated from the other by the value of the SUBSEP variable. Thus, the following two index operations shall be equivalent: var[expr1, expr2, ... exprn] var[expr1 SUBSEP expr2 SUBSEP ... SUBSEP exprn] The application shall ensure that a multi-dimensioned index used with the in operator is parenthesized. The in operator, which tests for the existence of a particular array element, shall not cause that element to exist. Any other reference to a nonexistent array element shall automatically create it. Comparisons (with the '<', "<=", "!=", "==", '>', and ">=" operators) shall be made numerically if both operands are numeric, if one is numeric and the other has a string value that is a numeric string, or if one is numeric and the other has the uninitialized value. Otherwise, operands shall be converted to strings as required and a string comparison shall be made as follows: * For the "!=" and "==" operators, the strings should be compared to check if they are identical but may be compared using the locale-specific collation sequence to check if they collate equally. * For the other operators, the strings shall be compared using the locale-specific collation sequence. The value of the comparison expression shall be 1 if the relation is true, or 0 if the relation is false. Variables and Special Variables Variables can be used in an awk program by referencing them. With the exception of function parameters (see User-Defined Functions), they are not explicitly declared. Function parameter names shall be local to the function; all other variable names shall be global. The same name shall not be used as both a function parameter name and as the name of a function or a special awk variable. The same name shall not be used both as a variable name with global scope and as the name of a function. The same name shall not be used within the same scope both as a scalar variable and as an array. Uninitialized variables, including scalar variables, array elements, and field variables, shall have an uninitialized value. An uninitialized value shall have both a numeric value of zero and a string value of the empty string. Evaluation of variables with an uninitialized value, to either string or numeric, shall be determined by the context in which they are used. Field variables shall be designated by a '$' followed by a number or numerical expression. The effect of the field number expression evaluating to anything other than a non-negative integer is unspecified; uninitialized variables or string values need not be converted to numeric values in this context. New field variables can be created by assigning a value to them. References to nonexistent fields (that is, fields after $NF), shall evaluate to the uninitialized value. Such references shall not create new fields. However, assigning to a nonexistent field (for example, $(NF+2)=5) shall increase the value of NF; create any intervening fields with the uninitialized value; and cause the value of $0 to be recomputed, with the fields being separated by the value of OFS. Each field variable shall have a string value or an uninitialized value when created. Field variables shall have the uninitialized value when created from $0 using FS and the variable does not contain any characters. If appropriate, the field variable shall be considered a numeric string (see Expressions in awk). Implementations shall support the following other special variables that are set by awk: ARGC The number of elements in the ARGV array. ARGV An array of command line arguments, excluding options and the program argument, numbered from zero to ARGC-1. The arguments in ARGV can be modified or added to; ARGC can be altered. As each input file ends, awk shall treat the next non-null element of ARGV, up to the current value of ARGC-1, inclusive, as the name of the next input file. Thus, setting an element of ARGV to null means that it shall not be treated as an input file. The name '-' indicates the standard input. If an argument matches the format of an assignment operand, this argument shall be treated as an assignment rather than a file argument. CONVFMT The printf format for converting numbers to strings (except for output statements, where OFMT is used); "%.6g" by default. ENVIRON An array representing the value of the environment, as described in the exec functions defined in the System Interfaces volume of POSIX.12017. The indices of the array shall be strings consisting of the names of the environment variables, and the value of each array element shall be a string consisting of the value of that variable. If appropriate, the environment variable shall be considered a numeric string (see Expressions in awk); the array element shall also have its numeric value. In all cases where the behavior of awk is affected by environment variables (including the environment of any commands that awk executes via the system function or via pipeline redirections with the print statement, the printf statement, or the getline function), the environment used shall be the environment at the time awk began executing; it is implementation-defined whether any modification of ENVIRON affects this environment. FILENAME A pathname of the current input file. Inside a BEGIN action the value is undefined. Inside an END action the value shall be the name of the last input file processed. FNR The ordinal number of the current record in the current file. Inside a BEGIN action the value shall be zero. Inside an END action the value shall be the number of the last record processed in the last file processed. FS Input field separator regular expression; a <space> by default. NF The number of fields in the current record. Inside a BEGIN action, the use of NF is undefined unless a getline function without a var argument is executed previously. Inside an END action, NF shall retain the value it had for the last record read, unless a subsequent, redirected, getline function without a var argument is performed prior to entering the END action. NR The ordinal number of the current record from the start of input. Inside a BEGIN action the value shall be zero. Inside an END action the value shall be the number of the last record processed. OFMT The printf format for converting numbers to strings in output statements (see Output Statements); "%.6g" by default. The result of the conversion is unspecified if the value of OFMT is not a floating-point format specification. OFS The print statement output field separator; <space> by default. ORS The print statement output record separator; a <newline> by default. RLENGTH The length of the string matched by the match function. RS The first character of the string value of RS shall be the input record separator; a <newline> by default. If RS contains more than one character, the results are unspecified. If RS is null, then records are separated by sequences consisting of a <newline> plus one or more blank lines, leading or trailing blank lines shall not result in empty records at the beginning or end of the input, and a <newline> shall always be a field separator, no matter what the value of FS is. RSTART The starting position of the string matched by the match function, numbering from 1. This shall always be equivalent to the return value of the match function. SUBSEP The subscript separator string for multi-dimensional arrays; the default value is implementation-defined. Regular Expressions The awk utility shall make use of the extended regular expression notation (see the Base Definitions volume of POSIX.12017, Section 9.4, Extended Regular Expressions) except that it shall allow the use of C-language conventions for escaping special characters within the EREs, as specified in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v') and the following table; these escape sequences shall be recognized both inside and outside bracket expressions. Note that records need not be separated by <newline> characters and string constants can contain <newline> characters, so even the "\n" sequence is valid in awk EREs. Using a <slash> character within an ERE requires the escaping shown in the following table. Table 4-2: Escape Sequences in awk Escape Sequence Description Meaning \" <backslash> <quotation-mark> <quotation-mark> character \/ <backslash> <slash> <slash> character \ddd A <backslash> character followed The character whose encoding is by the longest sequence of one, represented by the one, two, or two, or three octal-digit three-digit octal integer. Multi- characters (01234567). If all of byte characters require multiple, the digits are 0 (that is, concatenated escape sequences of representation of the NUL this type, including the leading character), the behavior is <backslash> for each byte. undefined. \c A <backslash> character followed Undefined by any character not described in this table or in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v'). A regular expression can be matched against a specific field or string by using one of the two regular expression matching operators, '~' and "!~". These operators shall interpret their right-hand operand as a regular expression and their left-hand operand as a string. If the regular expression matches the string, the '~' expression shall evaluate to a value of 1, and the "!~" expression shall evaluate to a value of 0. (The regular expression matching operation is as defined by the term matched in the Base Definitions volume of POSIX.12017, Section 9.1, Regular Expression Definitions, where a match occurs on any part of the string unless the regular expression is limited with the <circumflex> or <dollar-sign> special characters.) If the regular expression does not match the string, the '~' expression shall evaluate to a value of 0, and the "!~" expression shall evaluate to a value of 1. If the right-hand operand is any expression other than the lexical token ERE, the string value of the expression shall be interpreted as an extended regular expression, including the escape conventions described above. Note that these same escape conventions shall also be applied in determining the value of a string literal (the lexical token STRING), and thus shall be applied a second time when a string literal is used in this context. When an ERE token appears as an expression in any context other than as the right-hand of the '~' or "!~" operator or as one of the built-in function arguments described below, the value of the resulting expression shall be the equivalent of: $0 ~ /ere/ The ere argument to the gsub, match, sub functions, and the fs argument to the split function (see String Functions) shall be interpreted as extended regular expressions. These can be either ERE tokens or arbitrary expressions, and shall be interpreted in the same manner as the right-hand side of the '~' or "!~" operator. An extended regular expression can be used to separate fields by assigning a string containing the expression to the built-in variable FS, either directly or as a consequence of using the -F sepstring option. The default value of the FS variable shall be a single <space>. The following describes FS behavior: 1. If FS is a null string, the behavior is unspecified. 2. If FS is a single character: a. If FS is <space>, skip leading and trailing <blank> and <newline> characters; fields shall be delimited by sets of one or more <blank> or <newline> characters. b. Otherwise, if FS is any other character c, fields shall be delimited by each single occurrence of c. 3. Otherwise, the string value of FS shall be considered to be an extended regular expression. Each occurrence of a sequence matching the extended regular expression shall delimit fields. Except for the '~' and "!~" operators, and in the gsub, match, split, and sub built-in functions, ERE matching shall be based on input records; that is, record separator characters (the first character of the value of the variable RS, <newline> by default) cannot be embedded in the expression, and no expression shall match the record separator character. If the record separator is not <newline>, <newline> characters embedded in the expression can be matched. For the '~' and "!~" operators, and in those four built-in functions, ERE matching shall be based on text strings; that is, any character (including <newline> and the record separator) can be embedded in the pattern, and an appropriate pattern shall match any character. However, in all awk ERE matching, the use of one or more NUL characters in the pattern, input record, or text string produces undefined results. Patterns A pattern is any valid expression, a range specified by two expressions separated by a comma, or one of the two special patterns BEGIN or END. Special Patterns The awk utility shall recognize two special patterns, BEGIN and END. Each BEGIN pattern shall be matched once and its associated action executed before the first record of input is readexcept possibly by use of the getline function (see Input/Output and General Functions) in a prior BEGIN actionand before command line assignment is done. Each END pattern shall be matched once and its associated action executed after the last record of input has been read. These two patterns shall have associated actions. BEGIN and END shall not combine with other patterns. Multiple BEGIN and END patterns shall be allowed. The actions associated with the BEGIN patterns shall be executed in the order specified in the program, as are the END actions. An END pattern can precede a BEGIN pattern in a program. If an awk program consists of only actions with the pattern BEGIN, and the BEGIN action contains no getline function, awk shall exit without reading its input when the last statement in the last BEGIN action is executed. If an awk program consists of only actions with the pattern END or only actions with the patterns BEGIN and END, the input shall be read before the statements in the END actions are executed. Expression Patterns An expression pattern shall be evaluated as if it were an expression in a Boolean context. If the result is true, the pattern shall be considered to match, and the associated action (if any) shall be executed. If the result is false, the action shall not be executed. Pattern Ranges A pattern range consists of two expressions separated by a comma; in this case, the action shall be performed for all records between a match of the first expression and the following match of the second expression, inclusive. At this point, the pattern range can be repeated starting at input records subsequent to the end of the matched range. Actions An action is a sequence of statements as shown in the grammar in Grammar. Any single statement can be replaced by a statement list enclosed in curly braces. The application shall ensure that statements in a statement list are separated by <newline> or <semicolon> characters. Statements in a statement list shall be executed sequentially in the order that they appear. The expression acting as the conditional in an if statement shall be evaluated and if it is non-zero or non-null, the following statement shall be executed; otherwise, if else is present, the statement following the else shall be executed. The if, while, do...while, for, break, and continue statements are based on the ISO C standard (see Section 1.1.2, Concepts Derived from the ISO C Standard), except that the Boolean expressions shall be treated as described in Expressions in awk, and except in the case of: for (variable in array) which shall iterate, assigning each index of array to variable in an unspecified order. The results of adding new elements to array within such a for loop are undefined. If a break or continue statement occurs outside of a loop, the behavior is undefined. The delete statement shall remove an individual array element. Thus, the following code deletes an entire array: for (index in array) delete array[index] The next statement shall cause all further processing of the current input record to be abandoned. The behavior is undefined if a next statement appears or is invoked in a BEGIN or END action. The exit statement shall invoke all END actions in the order in which they occur in the program source and then terminate the program without reading further input. An exit statement inside an END action shall terminate the program without further execution of END actions. If an expression is specified in an exit statement, its numeric value shall be the exit status of awk, unless subsequent errors are encountered or a subsequent exit statement with an expression is executed. Output Statements Both print and printf statements shall write to standard output by default. The output shall be written to the location specified by output_redirection if one is supplied, as follows: > expression >> expression | expression In all cases, the expression shall be evaluated to produce a string that is used as a pathname into which to write (for '>' or ">>") or as a command to be executed (for '|'). Using the first two forms, if the file of that name is not currently open, it shall be opened, creating it if necessary and using the first form, truncating the file. The output then shall be appended to the file. As long as the file remains open, subsequent calls in which expression evaluates to the same string value shall simply append output to the file. The file remains open until the close function (see Input/Output and General Functions) is called with an expression that evaluates to the same string value. The third form shall write output onto a stream piped to the input of a command. The stream shall be created if no stream is currently open with the value of expression as its command name. The stream created shall be equivalent to one created by a call to the popen() function defined in the System Interfaces volume of POSIX.12017 with the value of expression as the command argument and a value of w as the mode argument. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value shall write output to the existing stream. The stream shall remain open until the close function (see Input/Output and General Functions) is called with an expression that evaluates to the same string value. At that time, the stream shall be closed as if by a call to the pclose() function defined in the System Interfaces volume of POSIX.12017. As described in detail by the grammar in Grammar, these output statements shall take a <comma>-separated list of expressions referred to in the grammar by the non-terminal symbols expr_list, print_expr_list, or print_expr_list_opt. This list is referred to here as the expression list, and each member is referred to as an expression argument. The print statement shall write the value of each expression argument onto the indicated output stream separated by the current output field separator (see variable OFS above), and terminated by the output record separator (see variable ORS above). All expression arguments shall be taken as strings, being converted if necessary; this conversion shall be as described in Expressions in awk, with the exception that the printf format in OFMT shall be used instead of the value in CONVFMT. An empty expression list shall stand for the whole input record ($0). The printf statement shall produce output based on a notation similar to the File Format Notation used to describe file formats in this volume of POSIX.12017 (see the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation). Output shall be produced as specified with the first expression argument as the string format and subsequent expression arguments as the strings arg1 to argn, inclusive, with the following exceptions: 1. The format shall be an actual character string rather than a graphical representation. Therefore, it cannot contain empty character positions. The <space> in the format string, in any context other than a flag of a conversion specification, shall be treated as an ordinary character that is copied to the output. 2. If the character set contains a '' character and that character appears in the format string, it shall be treated as an ordinary character that is copied to the output. 3. The escape sequences beginning with a <backslash> character shall be treated as sequences of ordinary characters that are copied to the output. Note that these same sequences shall be interpreted lexically by awk when they appear in literal strings, but they shall not be treated specially by the printf statement. 4. A field width or precision can be specified as the '*' character instead of a digit string. In this case the next argument from the expression list shall be fetched and its numeric value taken as the field width or precision. 5. The implementation shall not precede or follow output from the d or u conversion specifier characters with <blank> characters not specified by the format string. 6. The implementation shall not precede output from the o conversion specifier character with leading zeros not specified by the format string. 7. For the c conversion specifier character: if the argument has a numeric value, the character whose encoding is that value shall be output. If the value is zero or is not the encoding of any character in the character set, the behavior is undefined. If the argument does not have a numeric value, the first character of the string value shall be output; if the string does not contain any characters, the behavior is undefined. 8. For each conversion specification that consumes an argument, the next expression argument shall be evaluated. With the exception of the c conversion specifier character, the value shall be converted (according to the rules specified in Expressions in awk) to the appropriate type for the conversion specification. 9. If there are insufficient expression arguments to satisfy all the conversion specifications in the format string, the behavior is undefined. 10. If any character sequence in the format string begins with a '%' character, but does not form a valid conversion specification, the behavior is unspecified. Both print and printf can output at least {LINE_MAX} bytes. Functions The awk language has a variety of built-in functions: arithmetic, string, input/output, and general. Arithmetic Functions The arithmetic functions, except for int, shall be based on the ISO C standard (see Section 1.1.2, Concepts Derived from the ISO C Standard). The behavior is undefined in cases where the ISO C standard specifies that an error be returned or that the behavior is undefined. Although the grammar (see Grammar) permits built-in functions to appear with no arguments or parentheses, unless the argument or parentheses are indicated as optional in the following list (by displaying them within the "[]" brackets), such use is undefined. atan2(y,x) Return arctangent of y/x in radians in the range [-,]. cos(x) Return cosine of x, where x is in radians. sin(x) Return sine of x, where x is in radians. exp(x) Return the exponential function of x. log(x) Return the natural logarithm of x. sqrt(x) Return the square root of x. int(x) Return the argument truncated to an integer. Truncation shall be toward 0 when x>0. rand() Return a random number n, such that 0n<1. srand([expr]) Set the seed value for rand to expr or use the time of day if expr is omitted. The previous seed value shall be returned. String Functions The string functions in the following list shall be supported. Although the grammar (see Grammar) permits built-in functions to appear with no arguments or parentheses, unless the argument or parentheses are indicated as optional in the following list (by displaying them within the "[]" brackets), such use is undefined. gsub(ere, repl[, in]) Behave like sub (see below), except that it shall replace all occurrences of the regular expression (like the ed utility global substitute) in $0 or in the in argument, when specified. index(s, t) Return the position, in characters, numbering from 1, in string s where string t first occurs, or zero if it does not occur at all. length[([s])] Return the length, in characters, of its argument taken as a string, or of the whole record, $0, if there is no argument. match(s, ere) Return the position, in characters, numbering from 1, in string s where the extended regular expression ere occurs, or zero if it does not occur at all. RSTART shall be set to the starting position (which is the same as the returned value), zero if no match is found; RLENGTH shall be set to the length of the matched string, -1 if no match is found. split(s, a[, fs ]) Split the string s into array elements a[1], a[2], ..., a[n], and return n. All elements of the array shall be deleted before the split is performed. The separation shall be done with the ERE fs or with the field separator FS if fs is not given. Each array element shall have a string value when created and, if appropriate, the array element shall be considered a numeric string (see Expressions in awk). The effect of a null string as the value of fs is unspecified. sprintf(fmt, expr, expr, ...) Format the expressions according to the printf format given by fmt and return the resulting string. sub(ere, repl[, in ]) Substitute the string repl in place of the first instance of the extended regular expression ERE in string in and return the number of substitutions. An <ampersand> ('&') appearing in the string repl shall be replaced by the string from in that matches the ERE. An <ampersand> preceded with a <backslash> shall be interpreted as the literal <ampersand> character. An occurrence of two consecutive <backslash> characters shall be interpreted as just a single literal <backslash> character. Any other occurrence of a <backslash> (for example, preceding any other character) shall be treated as a literal <backslash> character. Note that if repl is a string literal (the lexical token STRING; see Grammar), the handling of the <ampersand> character occurs after any lexical processing, including any lexical <backslash>-escape sequence processing. If in is specified and it is not an lvalue (see Expressions in awk), the behavior is undefined. If in is omitted, awk shall use the current record ($0) in its place. substr(s, m[, n ]) Return the at most n-character substring of s that begins at position m, numbering from 1. If n is omitted, or if n specifies more characters than are left in the string, the length of the substring shall be limited by the length of the string s. tolower(s) Return a string based on the string s. Each character in s that is an uppercase letter specified to have a tolower mapping by the LC_CTYPE category of the current locale shall be replaced in the returned string by the lowercase letter specified by the mapping. Other characters in s shall be unchanged in the returned string. toupper(s) Return a string based on the string s. Each character in s that is a lowercase letter specified to have a toupper mapping by the LC_CTYPE category of the current locale is replaced in the returned string by the uppercase letter specified by the mapping. Other characters in s are unchanged in the returned string. All of the preceding functions that take ERE as a parameter expect a pattern or a string valued expression that is a regular expression as defined in Regular Expressions. Input/Output and General Functions The input/output and general functions are: close(expression) Close the file or pipe opened by a print or printf statement or a call to getline with the same string- valued expression. The limit on the number of open expression arguments is implementation-defined. If the close was successful, the function shall return zero; otherwise, it shall return non-zero. expression | getline [var] Read a record of input from a stream piped from the output of a command. The stream shall be created if no stream is currently open with the value of expression as its command name. The stream created shall be equivalent to one created by a call to the popen() function with the value of expression as the command argument and a value of r as the mode argument. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value shall read subsequent records from the stream. The stream shall remain open until the close function is called with an expression that evaluates to the same string value. At that time, the stream shall be closed as if by a call to the pclose() function. If var is omitted, $0 and NF shall be set; otherwise, var shall be set and, if appropriate, it shall be considered a numeric string (see Expressions in awk). The getline operator can form ambiguous constructs when there are unparenthesized operators (including concatenate) to the left of the '|' (to the beginning of the expression containing getline). In the context of the '$' operator, '|' shall behave as if it had a lower precedence than '$'. The result of evaluating other operators is unspecified, and conforming applications shall parenthesize properly all such usages. getline Set $0 to the next input record from the current input file. This form of getline shall set the NF, NR, and FNR variables. getline var Set variable var to the next input record from the current input file and, if appropriate, var shall be considered a numeric string (see Expressions in awk). This form of getline shall set the FNR and NR variables. getline [var] < expression Read the next record of input from a named file. The expression shall be evaluated to produce a string that is used as a pathname. If the file of that name is not currently open, it shall be opened. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value shall read subsequent records from the file. The file shall remain open until the close function is called with an expression that evaluates to the same string value. If var is omitted, $0 and NF shall be set; otherwise, var shall be set and, if appropriate, it shall be considered a numeric string (see Expressions in awk). The getline operator can form ambiguous constructs when there are unparenthesized binary operators (including concatenate) to the right of the '<' (up to the end of the expression containing the getline). The result of evaluating such a construct is unspecified, and conforming applications shall parenthesize properly all such usages. system(expression) Execute the command given by expression in a manner equivalent to the system() function defined in the System Interfaces volume of POSIX.12017 and return the exit status of the command. All forms of getline shall return 1 for successful input, zero for end-of-file, and -1 for an error. Where strings are used as the name of a file or pipeline, the application shall ensure that the strings are textually identical. The terminology ``same string value'' implies that ``equivalent strings'', even those that differ only by <space> characters, represent different files. User-Defined Functions The awk language also provides user-defined functions. Such functions can be defined as: function name([parameter, ...]) { statements } A function can be referred to anywhere in an awk program; in particular, its use can precede its definition. The scope of a function is global. Function parameters, if present, can be either scalars or arrays; the behavior is undefined if an array name is passed as a parameter that the function uses as a scalar, or if a scalar expression is passed as a parameter that the function uses as an array. Function parameters shall be passed by value if scalar and by reference if array name. The number of parameters in the function definition need not match the number of parameters in the function call. Excess formal parameters can be used as local variables. If fewer arguments are supplied in a function call than are in the function definition, the extra parameters that are used in the function body as scalars shall evaluate to the uninitialized value until they are otherwise initialized, and the extra parameters that are used in the function body as arrays shall be treated as uninitialized arrays where each element evaluates to the uninitialized value until otherwise initialized. When invoking a function, no white space can be placed between the function name and the opening parenthesis. Function calls can be nested and recursive calls can be made upon functions. Upon return from any nested or recursive function call, the values of all of the calling function's parameters shall be unchanged, except for array parameters passed by reference. The return statement can be used to return a value. If a return statement appears outside of a function definition, the behavior is undefined. In the function definition, <newline> characters shall be optional before the opening brace and after the closing brace. Function definitions can appear anywhere in the program where a pattern-action pair is allowed. Grammar The grammar in this section and the lexical conventions in the following section shall together describe the syntax for awk programs. The general conventions for this style of grammar are described in Section 1.3, Grammar Conventions. A valid program can be represented as the non-terminal symbol program in the grammar. This formal syntax shall take precedence over the preceding text syntax description. %token NAME NUMBER STRING ERE %token FUNC_NAME /* Name followed by '(' without white space. */ /* Keywords */ %token Begin End /* 'BEGIN' 'END' */ %token Break Continue Delete Do Else /* 'break' 'continue' 'delete' 'do' 'else' */ %token Exit For Function If In /* 'exit' 'for' 'function' 'if' 'in' */ %token Next Print Printf Return While /* 'next' 'print' 'printf' 'return' 'while' */ /* Reserved function names */ %token BUILTIN_FUNC_NAME /* One token for the following: * atan2 cos sin exp log sqrt int rand srand * gsub index length match split sprintf sub * substr tolower toupper close system */ %token GETLINE /* Syntactically different from other built-ins. */ /* Two-character tokens. */ %token ADD_ASSIGN SUB_ASSIGN MUL_ASSIGN DIV_ASSIGN MOD_ASSIGN POW_ASSIGN /* '+=' '-=' '*=' '/=' '%=' '^=' */ %token OR AND NO_MATCH EQ LE GE NE INCR DECR APPEND /* '||' '&&' '!~' '==' '<=' '>=' '!=' '++' '--' '>>' */ /* One-character tokens. */ %token '{' '}' '(' ')' '[' ']' ',' ';' NEWLINE %token '+' '-' '*' '%' '^' '!' '>' '<' '|' '?' ':' '~' '$' '=' %start program %% program : item_list | item_list item ; item_list : /* empty */ | item_list item terminator ; item : action | pattern action | normal_pattern | Function NAME '(' param_list_opt ')' newline_opt action | Function FUNC_NAME '(' param_list_opt ')' newline_opt action ; param_list_opt : /* empty */ | param_list ; param_list : NAME | param_list ',' NAME ; pattern : normal_pattern | special_pattern ; normal_pattern : expr | expr ',' newline_opt expr ; special_pattern : Begin | End ; action : '{' newline_opt '}' | '{' newline_opt terminated_statement_list '}' | '{' newline_opt unterminated_statement_list '}' ; terminator : terminator NEWLINE | ';' | NEWLINE ; terminated_statement_list : terminated_statement | terminated_statement_list terminated_statement ; unterminated_statement_list : unterminated_statement | terminated_statement_list unterminated_statement ; terminated_statement : action newline_opt | If '(' expr ')' newline_opt terminated_statement | If '(' expr ')' newline_opt terminated_statement Else newline_opt terminated_statement | While '(' expr ')' newline_opt terminated_statement | For '(' simple_statement_opt ';' expr_opt ';' simple_statement_opt ')' newline_opt terminated_statement | For '(' NAME In NAME ')' newline_opt terminated_statement | ';' newline_opt | terminatable_statement NEWLINE newline_opt | terminatable_statement ';' newline_opt ; unterminated_statement : terminatable_statement | If '(' expr ')' newline_opt unterminated_statement | If '(' expr ')' newline_opt terminated_statement Else newline_opt unterminated_statement | While '(' expr ')' newline_opt unterminated_statement | For '(' simple_statement_opt ';' expr_opt ';' simple_statement_opt ')' newline_opt unterminated_statement | For '(' NAME In NAME ')' newline_opt unterminated_statement ; terminatable_statement : simple_statement | Break | Continue | Next | Exit expr_opt | Return expr_opt | Do newline_opt terminated_statement While '(' expr ')' ; simple_statement_opt : /* empty */ | simple_statement ; simple_statement : Delete NAME '[' expr_list ']' | expr | print_statement ; print_statement : simple_print_statement | simple_print_statement output_redirection ; simple_print_statement : Print print_expr_list_opt | Print '(' multiple_expr_list ')' | Printf print_expr_list | Printf '(' multiple_expr_list ')' ; output_redirection : '>' expr | APPEND expr | '|' expr ; expr_list_opt : /* empty */ | expr_list ; expr_list : expr | multiple_expr_list ; multiple_expr_list : expr ',' newline_opt expr | multiple_expr_list ',' newline_opt expr ; expr_opt : /* empty */ | expr ; expr : unary_expr | non_unary_expr ; unary_expr : '+' expr | '-' expr | unary_expr '^' expr | unary_expr '*' expr | unary_expr '/' expr | unary_expr '%' expr | unary_expr '+' expr | unary_expr '-' expr | unary_expr non_unary_expr | unary_expr '<' expr | unary_expr LE expr | unary_expr NE expr | unary_expr EQ expr | unary_expr '>' expr | unary_expr GE expr | unary_expr '~' expr | unary_expr NO_MATCH expr | unary_expr In NAME | unary_expr AND newline_opt expr | unary_expr OR newline_opt expr | unary_expr '?' expr ':' expr | unary_input_function ; non_unary_expr : '(' expr ')' | '!' expr | non_unary_expr '^' expr | non_unary_expr '*' expr | non_unary_expr '/' expr | non_unary_expr '%' expr | non_unary_expr '+' expr | non_unary_expr '-' expr | non_unary_expr non_unary_expr | non_unary_expr '<' expr | non_unary_expr LE expr | non_unary_expr NE expr | non_unary_expr EQ expr | non_unary_expr '>' expr | non_unary_expr GE expr | non_unary_expr '~' expr | non_unary_expr NO_MATCH expr | non_unary_expr In NAME | '(' multiple_expr_list ')' In NAME | non_unary_expr AND newline_opt expr | non_unary_expr OR newline_opt expr | non_unary_expr '?' expr ':' expr | NUMBER | STRING | lvalue | ERE | lvalue INCR | lvalue DECR | INCR lvalue | DECR lvalue | lvalue POW_ASSIGN expr | lvalue MOD_ASSIGN expr | lvalue MUL_ASSIGN expr | lvalue DIV_ASSIGN expr | lvalue ADD_ASSIGN expr | lvalue SUB_ASSIGN expr | lvalue '=' expr | FUNC_NAME '(' expr_list_opt ')' /* no white space allowed before '(' */ | BUILTIN_FUNC_NAME '(' expr_list_opt ')' | BUILTIN_FUNC_NAME | non_unary_input_function ; print_expr_list_opt : /* empty */ | print_expr_list ; print_expr_list : print_expr | print_expr_list ',' newline_opt print_expr ; print_expr : unary_print_expr | non_unary_print_expr ; unary_print_expr : '+' print_expr | '-' print_expr | unary_print_expr '^' print_expr | unary_print_expr '*' print_expr | unary_print_expr '/' print_expr | unary_print_expr '%' print_expr | unary_print_expr '+' print_expr | unary_print_expr '-' print_expr | unary_print_expr non_unary_print_expr | unary_print_expr '~' print_expr | unary_print_expr NO_MATCH print_expr | unary_print_expr In NAME | unary_print_expr AND newline_opt print_expr | unary_print_expr OR newline_opt print_expr | unary_print_expr '?' print_expr ':' print_expr ; non_unary_print_expr : '(' expr ')' | '!' print_expr | non_unary_print_expr '^' print_expr | non_unary_print_expr '*' print_expr | non_unary_print_expr '/' print_expr | non_unary_print_expr '%' print_expr | non_unary_print_expr '+' print_expr | non_unary_print_expr '-' print_expr | non_unary_print_expr non_unary_print_expr | non_unary_print_expr '~' print_expr | non_unary_print_expr NO_MATCH print_expr | non_unary_print_expr In NAME | '(' multiple_expr_list ')' In NAME | non_unary_print_expr AND newline_opt print_expr | non_unary_print_expr OR newline_opt print_expr | non_unary_print_expr '?' print_expr ':' print_expr | NUMBER | STRING | lvalue | ERE | lvalue INCR | lvalue DECR | INCR lvalue | DECR lvalue | lvalue POW_ASSIGN print_expr | lvalue MOD_ASSIGN print_expr | lvalue MUL_ASSIGN print_expr | lvalue DIV_ASSIGN print_expr | lvalue ADD_ASSIGN print_expr | lvalue SUB_ASSIGN print_expr | lvalue '=' print_expr | FUNC_NAME '(' expr_list_opt ')' /* no white space allowed before '(' */ | BUILTIN_FUNC_NAME '(' expr_list_opt ')' | BUILTIN_FUNC_NAME ; lvalue : NAME | NAME '[' expr_list ']' | '$' expr ; non_unary_input_function : simple_get | simple_get '<' expr | non_unary_expr '|' simple_get ; unary_input_function : unary_expr '|' simple_get ; simple_get : GETLINE | GETLINE lvalue ; newline_opt : /* empty */ | newline_opt NEWLINE ; This grammar has several ambiguities that shall be resolved as follows: * Operator precedence and associativity shall be as described in Table 4-1, Expressions in Decreasing Precedence in awk. * In case of ambiguity, an else shall be associated with the most immediately preceding if that would satisfy the grammar. * In some contexts, a <slash> ('/') that is used to surround an ERE could also be the division operator. This shall be resolved in such a way that wherever the division operator could appear, a <slash> is assumed to be the division operator. (There is no unary division operator.) Each expression in an awk program shall conform to the precedence and associativity rules, even when this is not needed to resolve an ambiguity. For example, because '$' has higher precedence than '++', the string "$x++--" is not a valid awk expression, even though it is unambiguously parsed by the grammar as "$(x++)--". One convention that might not be obvious from the formal grammar is where <newline> characters are acceptable. There are several obvious placements such as terminating a statement, and a <backslash> can be used to escape <newline> characters between any lexical tokens. In addition, <newline> characters without <backslash> characters can follow a comma, an open brace, logical AND operator ("&&"), logical OR operator ("||"), the do keyword, the else keyword, and the closing parenthesis of an if, for, or while statement. For example: { print $1, $2 } Lexical Conventions The lexical conventions for awk programs, with respect to the preceding grammar, shall be as follows: 1. Except as noted, awk shall recognize the longest possible token or delimiter beginning at a given point. 2. A comment shall consist of any characters beginning with the <number-sign> character and terminated by, but excluding the next occurrence of, a <newline>. Comments shall have no effect, except to delimit lexical tokens. 3. The <newline> shall be recognized as the token NEWLINE. 4. A <backslash> character immediately followed by a <newline> shall have no effect. 5. The token STRING shall represent a string constant. A string constant shall begin with the character '"'. Within a string constant, a <backslash> character shall be considered to begin an escape sequence as specified in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v'). In addition, the escape sequences in Table 4-2, Escape Sequences in awk shall be recognized. A <newline> shall not occur within a string constant. A string constant shall be terminated by the first unescaped occurrence of the character '"' after the one that begins the string constant. The value of the string shall be the sequence of all unescaped characters and values of escape sequences between, but not including, the two delimiting '"' characters. 6. The token ERE represents an extended regular expression constant. An ERE constant shall begin with the <slash> character. Within an ERE constant, a <backslash> character shall be considered to begin an escape sequence as specified in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation. In addition, the escape sequences in Table 4-2, Escape Sequences in awk shall be recognized. The application shall ensure that a <newline> does not occur within an ERE constant. An ERE constant shall be terminated by the first unescaped occurrence of the <slash> character after the one that begins the ERE constant. The extended regular expression represented by the ERE constant shall be the sequence of all unescaped characters and values of escape sequences between, but not including, the two delimiting <slash> characters. 7. A <blank> shall have no effect, except to delimit lexical tokens or within STRING or ERE tokens. 8. The token NUMBER shall represent a numeric constant. Its form and numeric value shall either be equivalent to the decimal- floating-constant token as specified by the ISO C standard, or it shall be a sequence of decimal digits and shall be evaluated as an integer constant in decimal. In addition, implementations may accept numeric constants with the form and numeric value equivalent to the hexadecimal-constant and hexadecimal-floating-constant tokens as specified by the ISO C standard. If the value is too large or too small to be representable (see Section 1.1.2, Concepts Derived from the ISO C Standard), the behavior is undefined. 9. A sequence of underscores, digits, and alphabetics from the portable character set (see the Base Definitions volume of POSIX.12017, Section 6.1, Portable Character Set), beginning with an <underscore> or alphabetic character, shall be considered a word. 10. The following words are keywords that shall be recognized as individual tokens; the name of the token is the same as the keyword: BEGIN delete END function in printf break do exit getline next return continue else for if print while 11. The following words are names of built-in functions and shall be recognized as the token BUILTIN_FUNC_NAME: atan2 gsub log split sub toupper close index match sprintf substr cos int rand sqrt system exp length sin srand tolower The above-listed keywords and names of built-in functions are considered reserved words. 12. The token NAME shall consist of a word that is not a keyword or a name of a built-in function and is not followed immediately (without any delimiters) by the '(' character. 13. The token FUNC_NAME shall consist of a word that is not a keyword or a name of a built-in function, followed immediately (without any delimiters) by the '(' character. The '(' character shall not be included as part of the token. 14. The following two-character sequences shall be recognized as the named tokens: Token Name Sequence Token Name Sequence ADD_ASSIGN += NO_MATCH !~ SUB_ASSIGN -= EQ == MUL_ASSIGN *= LE <= DIV_ASSIGN /= GE >= MOD_ASSIGN %= NE != POW_ASSIGN ^= INCR ++ OR || DECR -- AND && APPEND >> 15. The following single characters shall be recognized as tokens whose names are the character: <newline> { } ( ) [ ] , ; + - * % ^ ! > < | ? : ~ $ = There is a lexical ambiguity between the token ERE and the tokens '/' and DIV_ASSIGN. When an input sequence begins with a <slash> character in any syntactic context where the token '/' or DIV_ASSIGN could appear as the next token in a valid program, the longer of those two tokens that can be recognized shall be recognized. In any other syntactic context where the token ERE could appear as the next token in a valid program, the token ERE shall be recognized. EXIT STATUS top The following exit values shall be returned: 0 All input files were processed successfully. >0 An error occurred. The exit status can be altered within the program by using an exit expression. CONSEQUENCES OF ERRORS top If any file operand is specified and the named file cannot be accessed, awk shall write a diagnostic message to standard error and terminate without any further action. If the program specified by either the program operand or a progfile operand is not a valid awk program (as specified in the EXTENDED DESCRIPTION section), the behavior is undefined. The following sections are informative. APPLICATION USAGE top The index, length, match, and substr functions should not be confused with similar functions in the ISO C standard; the awk versions deal with characters, while the ISO C standard deals with bytes. Because the concatenation operation is represented by adjacent expressions rather than an explicit operator, it is often necessary to use parentheses to enforce the proper evaluation precedence. When using awk to process pathnames, it is recommended that LC_ALL, or at least LC_CTYPE and LC_COLLATE, are set to POSIX or C in the environment, since pathnames can contain byte sequences that do not form valid characters in some locales, in which case the utility's behavior would be undefined. In the POSIX locale each byte is a valid single-byte character, and therefore this problem is avoided. On implementations where the "==" operator checks if strings collate equally, applications needing to check whether strings are identical can use: length(a) == length(b) && index(a,b) == 1 On implementations where the "==" operator checks if strings are identical, applications needing to check whether strings collate equally can use: a <= b && a >= b EXAMPLES top The awk program specified in the command line is most easily specified within single-quotes (for example, 'program') for applications using sh, because awk programs commonly contain characters that are special to the shell, including double- quotes. In the cases where an awk program contains single-quote characters, it is usually easiest to specify most of the program as strings within single-quotes concatenated by the shell with quoted single-quote characters. For example: awk '/'\''/ { print "quote:", $0 }' prints all lines from the standard input containing a single- quote character, prefixed with quote:. The following are examples of simple awk programs: 1. Write to the standard output all input lines for which field 3 is greater than 5: $3 > 5 2. Write every tenth line: (NR % 10) == 0 3. Write any line with a substring matching the regular expression: /(G|D)(2[0-9][[:alpha:]]*)/ 4. Print any line with a substring containing a 'G' or 'D', followed by a sequence of digits and characters. This example uses character classes digit and alpha to match language- independent digit and alphabetic characters respectively: /(G|D)([[:digit:][:alpha:]]*)/ 5. Write any line in which the second field matches the regular expression and the fourth field does not: $2 ~ /xyz/ && $4 !~ /xyz/ 6. Write any line in which the second field contains a <backslash>: $2 ~ /\\/ 7. Write any line in which the second field contains a <backslash>. Note that <backslash>-escapes are interpreted twice; once in lexical processing of the string and once in processing the regular expression: $2 ~ "\\\\" 8. Write the second to the last and the last field in each line. Separate the fields by a <colon>: {OFS=":";print $(NF-1), $NF} 9. Write the line number and number of fields in each line. The three strings representing the line number, the <colon>, and the number of fields are concatenated and that string is written to standard output: {print NR ":" NF} 10. Write lines longer than 72 characters: length($0) > 72 11. Write the first two fields in opposite order separated by OFS: { print $2, $1 } 12. Same, with input fields separated by a <comma> or <space> and <tab> characters, or both: BEGIN { FS = ",[ \t]*|[ \t]+" } { print $2, $1 } 13. Add up the first column, print sum, and average: {s += $1 } END {print "sum is ", s, " average is", s/NR} 14. Write fields in reverse order, one per line (many lines out for each line in): { for (i = NF; i > 0; --i) print $i } 15. Write all lines between occurrences of the strings start and stop: /start/, /stop/ 16. Write all lines whose first field is different from the previous one: $1 != prev { print; prev = $1 } 17. Simulate echo: BEGIN { for (i = 1; i < ARGC; ++i) printf("%s%s", ARGV[i], i==ARGC-1?"\n":" ") } 18. Write the path prefixes contained in the PATH environment variable, one per line: BEGIN { n = split (ENVIRON["PATH"], path, ":") for (i = 1; i <= n; ++i) print path[i] } 19. If there is a file named input containing page headers of the form: Page # and a file named program that contains: /Page/ { $2 = n++; } { print } then the command line: awk -f program n=5 input prints the file input, filling in page numbers starting at 5. RATIONALE top This description is based on the new awk, ``nawk'', (see the referenced The AWK Programming Language), which introduced a number of new features to the historical awk: 1. New keywords: delete, do, function, return 2. New built-in functions: atan2, close, cos, gsub, match, rand, sin, srand, sub, system 3. New predefined variables: FNR, ARGC, ARGV, RSTART, RLENGTH, SUBSEP 4. New expression operators: ?, :, ,, ^ 5. The FS variable and the third argument to split, now treated as extended regular expressions. 6. The operator precedence, changed to more closely match the C language. Two examples of code that operate differently are: while ( n /= 10 > 1) ... if (!"wk" ~ /bwk/) ... Several features have been added based on newer implementations of awk: * Multiple instances of -f progfile are permitted. * The new option -v assignment. * The new predefined variable ENVIRON. * New built-in functions toupper and tolower. * More formatting capabilities are added to printf to match the ISO C standard. Earlier versions of this standard required implementations to support multiple adjacent <semicolon>s, lines with one or more <semicolon> before a rule (pattern-action pairs), and lines with only <semicolon>(s). These are not required by this standard and are considered poor programming practice, but can be accepted by an implementation of awk as an extension. The overall awk syntax has always been based on the C language, with a few features from the shell command language and other sources. Because of this, it is not completely compatible with any other language, which has caused confusion for some users. It is not the intent of the standard developers to address such issues. A few relatively minor changes toward making the language more compatible with the ISO C standard were made; most of these changes are based on similar changes in recent implementations, as described above. There remain several C-language conventions that are not in awk. One of the notable ones is the <comma> operator, which is commonly used to specify multiple expressions in the C language for statement. Also, there are various places where awk is more restrictive than the C language regarding the type of expression that can be used in a given context. These limitations are due to the different features that the awk language does provide. Regular expressions in awk have been extended somewhat from historical implementations to make them a pure superset of extended regular expressions, as defined by POSIX.12008 (see the Base Definitions volume of POSIX.12017, Section 9.4, Extended Regular Expressions). The main extensions are internationalization features and interval expressions. Historical implementations of awk have long supported <backslash>-escape sequences as an extension to extended regular expressions, and this extension has been retained despite inconsistency with other utilities. The number of escape sequences recognized in both extended regular expressions and strings has varied (generally increasing with time) among implementations. The set specified by POSIX.12008 includes most sequences known to be supported by popular implementations and by the ISO C standard. One sequence that is not supported is hexadecimal value escapes beginning with '\x'. This would allow values expressed in more than 9 bits to be used within awk as in the ISO C standard. However, because this syntax has a non- deterministic length, it does not permit the subsequent character to be a hexadecimal digit. This limitation can be dealt with in the C language by the use of lexical string concatenation. In the awk language, concatenation could also be a solution for strings, but not for extended regular expressions (either lexical ERE tokens or strings used dynamically as regular expressions). Because of this limitation, the feature has not been added to POSIX.12008. When a string variable is used in a context where an extended regular expression normally appears (where the lexical token ERE is used in the grammar) the string does not contain the literal <slash> characters. Some versions of awk allow the form: func name(args, ... ) { statements } This has been deprecated by the authors of the language, who asked that it not be specified. Historical implementations of awk produce an error if a next statement is executed in a BEGIN action, and cause awk to terminate if a next statement is executed in an END action. This behavior has not been documented, and it was not believed that it was necessary to standardize it. The specification of conversions between string and numeric values is much more detailed than in the documentation of historical implementations or in the referenced The AWK Programming Language. Although most of the behavior is designed to be intuitive, the details are necessary to ensure compatible behavior from different implementations. This is especially important in relational expressions since the types of the operands determine whether a string or numeric comparison is performed. From the perspective of an application developer, it is usually sufficient to expect intuitive behavior and to force conversions (by adding zero or concatenating a null string) when the type of an expression does not obviously match what is needed. The intent has been to specify historical practice in almost all cases. The one exception is that, in historical implementations, variables and constants maintain both string and numeric values after their original value is converted by any use. This means that referencing a variable or constant can have unexpected side-effects. For example, with historical implementations the following program: { a = "+2" b = 2 if (NR % 2) c = a + b if (a == b) print "numeric comparison" else print "string comparison" } would perform a numeric comparison (and output numeric comparison) for each odd-numbered line, but perform a string comparison (and output string comparison) for each even-numbered line. POSIX.12008 ensures that comparisons will be numeric if necessary. With historical implementations, the following program: BEGIN { OFMT = "%e" print 3.14 OFMT = "%f" print 3.14 } would output "3.140000e+00" twice, because in the second print statement the constant "3.14" would have a string value from the previous conversion. POSIX.12008 requires that the output of the second print statement be "3.140000". The behavior of historical implementations was seen as too unintuitive and unpredictable. It was pointed out that with the rules contained in early drafts, the following script would print nothing: BEGIN { y[1.5] = 1 OFMT = "%e" print y[1.5] } Therefore, a new variable, CONVFMT, was introduced. The OFMT variable is now restricted to affecting output conversions of numbers to strings and CONVFMT is used for internal conversions, such as comparisons or array indexing. The default value is the same as that for OFMT, so unless a program changes CONVFMT (which no historical program would do), it will receive the historical behavior associated with internal string conversions. The POSIX awk lexical and syntactic conventions are specified more formally than in other sources. Again the intent has been to specify historical practice. One convention that may not be obvious from the formal grammar as in other verbal descriptions is where <newline> characters are acceptable. There are several obvious placements such as terminating a statement, and a <backslash> can be used to escape <newline> characters between any lexical tokens. In addition, <newline> characters without <backslash> characters can follow a comma, an open brace, a logical AND operator ("&&"), a logical OR operator ("||"), the do keyword, the else keyword, and the closing parenthesis of an if, for, or while statement. For example: { print $1, $2 } The requirement that awk add a trailing <newline> to the program argument text is to simplify the grammar, making it match a text file in form. There is no way for an application or test suite to determine whether a literal <newline> is added or whether awk simply acts as if it did. POSIX.12008 requires several changes from historical implementations in order to support internationalization. Probably the most subtle of these is the use of the decimal-point character, defined by the LC_NUMERIC category of the locale, in representations of floating-point numbers. This locale-specific character is used in recognizing numeric input, in converting between strings and numeric values, and in formatting output. However, regardless of locale, the <period> character (the decimal-point character of the POSIX locale) is the decimal-point character recognized in processing awk programs (including assignments in command line arguments). This is essentially the same convention as the one used in the ISO C standard. The difference is that the C language includes the setlocale() function, which permits an application to modify its locale. Because of this capability, a C application begins executing with its locale set to the C locale, and only executes in the environment-specified locale after an explicit call to setlocale(). However, adding such an elaborate new feature to the awk language was seen as inappropriate for POSIX.12008. It is possible to execute an awk program explicitly in any desired locale by setting the environment in the shell. The undefined behavior resulting from NULs in extended regular expressions allows future extensions for the GNU gawk program to process binary data. The behavior in the case of invalid awk programs (including lexical, syntactic, and semantic errors) is undefined because it was considered overly limiting on implementations to specify. In most cases such errors can be expected to produce a diagnostic and a non-zero exit status. However, some implementations may choose to extend the language in ways that make use of certain invalid constructs. Other invalid constructs might be deemed worthy of a warning, but otherwise cause some reasonable behavior. Still other constructs may be very difficult to detect in some implementations. Also, different implementations might detect a given error during an initial parsing of the program (before reading any input files) while others might detect it when executing the program after reading some input. Implementors should be aware that diagnosing errors as early as possible and producing useful diagnostics can ease debugging of applications, and thus make an implementation more usable. The unspecified behavior from using multi-character RS values is to allow possible future extensions based on extended regular expressions used for record separators. Historical implementations take the first character of the string and ignore the others. Unspecified behavior when split(string,array,<null>) is used is to allow a proposed future extension that would split up a string into an array of individual characters. In the context of the getline function, equally good arguments for different precedences of the | and < operators can be made. Historical practice has been that: getline < "a" "b" is parsed as: ( getline < "a" ) "b" although many would argue that the intent was that the file ab should be read. However: getline < "x" + 1 parses as: getline < ( "x" + 1 ) Similar problems occur with the | version of getline, particularly in combination with $. For example: $"echo hi" | getline (This situation is particularly problematic when used in a print statement, where the |getline part might be a redirection of the print.) Since in most cases such constructs are not (or at least should not) be used (because they have a natural ambiguity for which there is no conventional parsing), the meaning of these constructs has been made explicitly unspecified. (The effect is that a conforming application that runs into the problem must parenthesize to resolve the ambiguity.) There appeared to be few if any actual uses of such constructs. Grammars can be written that would cause an error under these circumstances. Where backwards-compatibility is not a large consideration, implementors may wish to use such grammars. Some historical implementations have allowed some built-in functions to be called without an argument list, the result being a default argument list chosen in some ``reasonable'' way. Use of length as a synonym for length($0) is the only one of these forms that is thought to be widely known or widely used; this particular form is documented in various places (for example, most historical awk reference pages, although not in the referenced The AWK Programming Language) as legitimate practice. With this exception, default argument lists have always been undocumented and vaguely defined, and it is not at all clear how (or if) they should be generalized to user-defined functions. They add no useful functionality and preclude possible future extensions that might need to name functions without calling them. Not standardizing them seems the simplest course. The standard developers considered that length merited special treatment, however, since it has been documented in the past and sees possibly substantial use in historical programs. Accordingly, this usage has been made legitimate, but Issue 5 removed the obsolescent marking for XSI-conforming implementations and many otherwise conforming applications depend on this feature. In sub and gsub, if repl is a string literal (the lexical token STRING), then two consecutive <backslash> characters should be used in the string to ensure a single <backslash> will precede the <ampersand> when the resultant string is passed to the function. (For example, to specify one literal <ampersand> in the replacement string, use gsub(ERE, "\\&").) Historically, the only special character in the repl argument of sub and gsub string functions was the <ampersand> ('&') character and preceding it with the <backslash> character was used to turn off its special meaning. The description in the ISO POSIX2:1993 standard introduced behavior such that the <backslash> character was another special character and it was unspecified whether there were any other special characters. This description introduced several portability problems, some of which are described below, and so it has been replaced with the more historical description. Some of the problems include: * Historically, to create the replacement string, a script could use gsub(ERE, "\\&"), but with the ISO POSIX2:1993 standard wording, it was necessary to use gsub(ERE, "\\\\&"). The <backslash> characters are doubled here because all string literals are subject to lexical analysis, which would reduce each pair of <backslash> characters to a single <backslash> before being passed to gsub. * Since it was unspecified what the special characters were, for portable scripts to guarantee that characters are printed literally, each character had to be preceded with a <backslash>. (For example, a portable script had to use gsub(ERE, "\\h\\i") to produce a replacement string of "hi".) The description for comparisons in the ISO POSIX2:1993 standard did not properly describe historical practice because of the way numeric strings are compared as numbers. The current rules cause the following code: if (0 == "000") print "strange, but true" else print "not true" to do a numeric comparison, causing the if to succeed. It should be intuitively obvious that this is incorrect behavior, and indeed, no historical implementation of awk actually behaves this way. To fix this problem, the definition of numeric string was enhanced to include only those values obtained from specific circumstances (mostly external sources) where it is not possible to determine unambiguously whether the value is intended to be a string or a numeric. Variables that are assigned to a numeric string shall also be treated as a numeric string. (For example, the notion of a numeric string can be propagated across assignments.) In comparisons, all variables having the uninitialized value are to be treated as a numeric operand evaluating to the numeric value zero. Uninitialized variables include all types of variables including scalars, array elements, and fields. The definition of an uninitialized value in Variables and Special Variables is necessary to describe the value placed on uninitialized variables and on fields that are valid (for example, < $NF) but have no characters in them and to describe how these variables are to be used in comparisons. A valid field, such as $1, that has no characters in it can be obtained from an input line of "\t\t" when FS='\t'. Historically, the comparison ($1<10) was done numerically after evaluating $1 to the value zero. The phrase ``... also shall have the numeric value of the numeric string'' was removed from several sections of the ISO POSIX2:1993 standard because is specifies an unnecessary implementation detail. It is not necessary for POSIX.12008 to specify that these objects be assigned two different values. It is only necessary to specify that these objects may evaluate to two different values depending on context. Historical implementations of awk did not parse hexadecimal integer or floating constants like "0xa" and "0xap0". Due to an oversight, the 2001 through 2004 editions of this standard required support for hexadecimal floating constants. This was due to the reference to atof(). This version of the standard allows but does not require implementations to use atof() and includes a description of how floating-point numbers are recognized as an alternative to match historic behavior. The intent of this change is to allow implementations to recognize floating-point constants according to either the ISO/IEC 9899:1990 standard or ISO/IEC 9899:1999 standard, and to allow (but not require) implementations to recognize hexadecimal integer constants. Historical implementations of awk did not support floating-point infinities and NaNs in numeric strings; e.g., "-INF" and "NaN". However, implementations that use the atof() or strtod() functions to do the conversion picked up support for these values if they used a ISO/IEC 9899:1999 standard version of the function instead of a ISO/IEC 9899:1990 standard version. Due to an oversight, the 2001 through 2004 editions of this standard did not allow support for infinities and NaNs, but in this revision support is allowed (but not required). This is a silent change to the behavior of awk programs; for example, in the POSIX locale the expression: ("-INF" + 0 < 0) formerly had the value 0 because "-INF" converted to 0, but now it may have the value 0 or 1. FUTURE DIRECTIONS top A future version of this standard may require the "!=" and "==" operators to perform string comparisons by checking if the strings are identical (and not by checking if they collate equally). SEE ALSO top Section 1.3, Grammar Conventions, grep(1p), lex(1p), sed(1p) The Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation, Section 6.1, Portable Character Set, Chapter 8, Environment Variables, Chapter 9, Regular Expressions, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, atof(3p), exec(1p), isspace(3p), popen(3p), setlocale(3p), strtod(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 AWK(1P) Pages that refer to this page: bc(1p), colrm(1), join(1p), printf(1p), sed(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. kill(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training Other versions of this page are provided by these projects: coreutils procps-ng kill(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | ARGUMENTS | OPTIONS | EXIT STATUS | NOTES | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY KILL(1) User Commands KILL(1) NAME top kill - terminate a process SYNOPSIS top kill [-signal|-s signal|-p] [-q value] [-a] [--timeout milliseconds signal] [--] pid|name... kill -l [number] | -L DESCRIPTION top The command kill sends the specified signal to the specified processes or process groups. If no signal is specified, the TERM signal is sent. The default action for this signal is to terminate the process. This signal should be used in preference to the KILL signal (number 9), since a process may install a handler for the TERM signal in order to perform clean-up steps before terminating in an orderly fashion. If a process does not terminate after a TERM signal has been sent, then the KILL signal may be used; be aware that the latter signal cannot be caught, and so does not give the target process the opportunity to perform any clean-up before terminating. Most modern shells have a builtin kill command, with a usage rather similar to that of the command described here. The --all, --pid, and --queue options, and the possibility to specify processes by command name, are local extensions. If signal is 0, then no actual signal is sent, but error checking is still performed. ARGUMENTS top The list of processes to be signaled can be a mixture of names and PIDs. pid Each pid can be expressed in one of the following ways: n where n is larger than 0. The process with PID n is signaled. 0 All processes in the current process group are signaled. -1 All processes with a PID larger than 1 are signaled. -n where n is larger than 1. All processes in process group n are signaled. When an argument of the form '-n' is given, and it is meant to denote a process group, either a signal must be specified first, or the argument must be preceded by a '--' option, otherwise it will be taken as the signal to send. name All processes invoked using this name will be signaled. OPTIONS top -s, --signal signal The signal to send. It may be given as a name or a number. -l, --list [number] Print a list of signal names, or convert the given signal number to a name. The signals can be found in /usr/include/linux/signal.h. -L, --table Similar to -l, but it will print signal names and their corresponding numbers. -a, --all Do not restrict the command-name-to-PID conversion to processes with the same UID as the present process. -p, --pid Only print the process ID (PID) of the named processes, do not send any signals. -r, --require-handler Do not send the signal if it is not caught in userspace by the signalled process. --verbose Print PID(s) that will be signaled with kill along with the signal. -q, --queue value Send the signal using sigqueue(3) rather than kill(2). The value argument is an integer that is sent along with the signal. If the receiving process has installed a handler for this signal using the SA_SIGINFO flag to sigaction(2), then it can obtain this data via the si_sigval field of the siginfo_t structure. --timeout milliseconds signal Send a signal defined in the usual way to a process, followed by an additional signal after a specified delay. The --timeout option causes kill to wait for a period defined in milliseconds before sending a follow-up signal to the process. This feature is implemented using the Linux kernel PID file descriptor feature in order to guarantee that the follow-up signal is sent to the same process or not sent if the process no longer exists. Note that the operating system may re-use PIDs and implementing an equivalent feature in a shell using kill and sleep would be subject to races whereby the follow-up signal might be sent to a different process that used a recycled PID. The --timeout option can be specified multiple times: the signals are sent sequentially with the specified timeouts. The --timeout option can be combined with the --queue option. As an example, the following command sends the signals QUIT, TERM and KILL in sequence and waits for 1000 milliseconds between sending the signals: kill --verbose --timeout 1000 TERM --timeout 1000 KILL \ --signal QUIT 12345 EXIT STATUS top kill has the following exit status values: 0 success 1 failure 64 partial success (when more than one process specified) NOTES top Although it is possible to specify the TID (thread ID, see gettid(2)) of one of the threads in a multithreaded process as the argument of kill, the signal is nevertheless directed to the process (i.e., the entire thread group). In other words, it is not possible to send a signal to an explicitly selected thread in a multithreaded process. The signal will be delivered to an arbitrarily selected thread in the target process that is not blocking the signal. For more details, see signal(7) and the description of CLONE_THREAD in clone(2). Various shells provide a builtin kill command that is preferred in relation to the kill(1) executable described by this manual. The easiest way to ensure one is executing the command described in this page is to use the full path when calling the command, for example: /bin/kill --version AUTHORS top Salvatore Valente <svalente@mit.edu>, Karel Zak <kzak@redhat.com> The original version was taken from BSD 4.4. SEE ALSO top bash(1), tcsh(1), sigaction(2), kill(2), sigqueue(3), signal(7) REPORTING BUGS top For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY top The kill command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at https://www.kernel.org/pub/linux/utils/util-linux/. If you have a bug report for this manual page, send it to util-linux@vger.kernel.org. This page was obtained from the project's upstream Git repository git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org util-linux 2.39.594-1e0ad 2023-07-19 KILL(1) Pages that refer to this page: fuser(1), kill(1), killall(1), pgrep(1), pmsignal(1), skill(1), tcpdump(1), timeout(1), xargs(1), kill(2), sigaction(2), signal(2), posix_spawn(3), signal(7), ldattach(8), lsof(8), systemd-coredump(8), tcpdump(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Clean up all zombie processes by instantly killing their parent process with SIGKILL signal. Bash Command:<START>kill -9 $(ps -A -ostat,ppid | grep -e '[zZ]'| awk '{ print $2 }')<END>

Clean up all zombie processes by sending SIGTERM signal to their parent process, which requests them to terminate.

kill $(ps -A -ostat,ppid | awk '/[zZ]/{print $2}')

['ps', 'awk', 'kill']

Output a Bash command to accomplish the following task. Task: Clean up all zombie processes by sending SIGTERM signal to their parent process, which requests them to terminate. Bash Command:<START>kill $(ps -A -ostat,ppid | awk '/[zZ]/{print $2}')<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # ps\n\n> Information about running processes.\n> More information: <https://manned.org/ps>.\n\n- List all running processes:\n\n`ps aux`\n\n- List all running processes including the full command string:\n\n`ps auxww`\n\n- Search for a process that matches a string:\n\n`ps aux | grep {{string}}`\n\n- List all processes of the current user in extra full format:\n\n`ps --user $(id -u) -F`\n\n- List all processes of the current user as a tree:\n\n`ps --user $(id -u) f`\n\n- Get the parent PID of a process:\n\n`ps -o ppid= -p {{pid}}`\n\n- Sort processes by memory consumption:\n\n`ps --sort size`\n # awk\n\n> A versatile programming language for working on files.\n> More information: <https://github.com/onetrueawk/awk>.\n\n- Print the fifth column (a.k.a. field) in a space-separated file:\n\n`awk '{print $5}' {{path/to/file}}`\n\n- Print the second column of the lines containing "foo" in a space-separated file:\n\n`awk '/{{foo}}/ {print $2}' {{path/to/file}}`\n\n- Print the last column of each line in a file, using a comma (instead of space) as a field separator:\n\n`awk -F ',' '{print $NF}' {{path/to/file}}`\n\n- Sum the values in the first column of a file and print the total:\n\n`awk '{s+=$1} END {print s}' {{path/to/file}}`\n\n- Print every third line starting from the first line:\n\n`awk 'NR%3==1' {{path/to/file}}`\n\n- Print different values based on conditions:\n\n`awk '{if ($1 == "foo") print "Exact match foo"; else if ($1 ~ "bar") print "Partial match bar"; else print "Baz"}' {{path/to/file}}`\n\n- Print all lines where the 10th column value equals the specified value:\n\n`awk '($10 == {{value}})'`\n\n- Print all the lines which the 10th column value is between a min and a max:\n\n`awk '($10 >= {{min_value}} && $10 <= {{max_value}})'`\n # kill\n\n> Sends a signal to a process, usually related to stopping the process.\n> All signals except for SIGKILL and SIGSTOP can be intercepted by the process to perform a clean exit.\n> More information: <https://manned.org/kill>.\n\n- Terminate a program using the default SIGTERM (terminate) signal:\n\n`kill {{process_id}}`\n\n- List signal values and their corresponding names (to be used without the `SIG` prefix):\n\n`kill -{{L|-table}}`\n\n- Terminate a background job:\n\n`kill %{{job_id}}`\n\n- Terminate a program using the SIGHUP (hang up) signal. Many daemons will reload instead of terminating:\n\n`kill -{{1|HUP}} {{process_id}}`\n\n- Terminate a program using the SIGINT (interrupt) signal. This is typically initiated by the user pressing `Ctrl + C`:\n\n`kill -{{2|INT}} {{process_id}}`\n\n- Signal the operating system to immediately terminate a program (which gets no chance to capture the signal):\n\n`kill -{{9|KILL}} {{process_id}}`\n\n- Signal the operating system to pause a program until a SIGCONT ("continue") signal is received:\n\n`kill -{{17|STOP}} {{process_id}}`\n\n- Send a `SIGUSR1` signal to all processes with the given GID (group id):\n\n`kill -{{SIGUSR1}} -{{group_id}}`\n Task: Clean up all zombie processes by sending SIGTERM signal to their parent process, which requests them to terminate. Bash Command:<START>kill $(ps -A -ostat,ppid | awk '/[zZ]/{print $2}')<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: ps(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training ps(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SIMPLE PROCESS SELECTION | PROCESS SELECTION BY LIST | OUTPUT FORMAT CONTROL | OUTPUT MODIFIERS | THREAD DISPLAY | OTHER INFORMATION | NOTES | PROCESS FLAGS | PROCESS STATE CODES | OBSOLETE SORT KEYS | AIX FORMAT DESCRIPTORS | STANDARD FORMAT SPECIFIERS | ENVIRONMENT VARIABLES | PERSONALITY | BUGS | SEE ALSO | STANDARDS | AUTHOR | COLOPHON PS(1) User Commands PS(1) NAME top ps - report a snapshot of the current processes. SYNOPSIS top ps [options] DESCRIPTION top ps displays information about a selection of the active processes. If you want a repetitive update of the selection and the displayed information, use top instead. This version of ps accepts several kinds of options: 1 UNIX options, which may be grouped and must be preceded by a dash. 2 BSD options, which may be grouped and must not be used with a dash. 3 GNU long options, which are preceded by two dashes. Options of different types may be freely mixed, but conflicts can appear. There are some synonymous options, which are functionally identical, due to the many standards and ps implementations that this ps is compatible with. By default, ps selects all processes with the same effective user ID (euid=EUID) as the current user and associated with the same terminal as the invoker. It displays the process ID (pid=PID), the terminal associated with the process (tname=TTY), the cumulated CPU time in [DD-]hh:mm:ss format (time=TIME), and the executable name (ucmd=CMD). Output is unsorted by default. The use of BSD-style options will add process state (stat=STAT) to the default display and show the command args (args=COMMAND) instead of the executable name. You can override this with the PS_FORMAT environment variable. The use of BSD-style options will also change the process selection to include processes on other terminals (TTYs) that are owned by you; alternately, this may be described as setting the selection to be the set of all processes filtered to exclude processes owned by other users or not on a terminal. These effects are not considered when options are described as being "identical" below, so -M will be considered identical to Z and so on. Except as described below, process selection options are additive. The default selection is discarded, and then the selected processes are added to the set of processes to be displayed. A process will thus be shown if it meets any of the given selection criteria. EXAMPLES top To see every process on the system using standard syntax: ps -e ps -ef ps -eF ps -ely To see every process on the system using BSD syntax: ps ax ps axu To print a process tree: ps -ejH ps axjf To get info about threads: ps -eLf ps axms To get security info: ps -eo euser,ruser,suser,fuser,f,comm,label ps axZ ps -eM To see every process running as root (real & effective ID) in user format: ps -U root -u root u To see every process with a user-defined format: ps -eo pid,tid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm ps axo stat,euid,ruid,tty,tpgid,sess,pgrp,ppid,pid,pcpu,comm ps -Ao pid,tt,user,fname,tmout,f,wchan Print only the process IDs of syslogd: ps -C syslogd -o pid= Print only the name of PID 42: ps -q 42 -o comm= SIMPLE PROCESS SELECTION top a Lift the BSD-style "only yourself" restriction, which is imposed upon the set of all processes when some BSD-style (without "-") options are used or when the ps personality setting is BSD-like. The set of processes selected in this manner is in addition to the set of processes selected by other means. An alternate description is that this option causes ps to list all processes with a terminal (tty), or to list all processes when used together with the x option. -A Select all processes. Identical to -e. -a Select all processes except both session leaders (see getsid(2)) and processes not associated with a terminal. -d Select all processes except session leaders. --deselect Select all processes except those that fulfill the specified conditions (negates the selection). Identical to -N. -e Select all processes. Identical to -A. g Really all, even session leaders. This flag is obsolete and may be discontinued in a future release. It is normally implied by the a flag, and is only useful when operating in the sunos4 personality. -N Select all processes except those that fulfill the specified conditions (negates the selection). Identical to --deselect. T Select all processes associated with this terminal. Identical to the t option without any argument. r Restrict the selection to only running processes. x Lift the BSD-style "must have a tty" restriction, which is imposed upon the set of all processes when some BSD-style (without "-") options are used or when the ps personality setting is BSD-like. The set of processes selected in this manner is in addition to the set of processes selected by other means. An alternate description is that this option causes ps to list all processes owned by you (same EUID as ps), or to list all processes when used together with the a option. PROCESS SELECTION BY LIST top These options accept a single argument in the form of a blank-separated or comma-separated list. They can be used multiple times. For example: ps -p "1 2" -p 3,4 123 Identical to --pid 123. +123 Identical to --sid 123. -123 Select by process group ID (PGID). -C cmdlist Select by command name. This selects the processes whose executable name is given in cmdlist. NOTE: The command name is not the same as the command line. Previous versions of procps and the kernel truncated this command name to 15 characters. This limitation is no longer present in both. If you depended on matching only 15 characters, you may no longer get a match. -G grplist Select by real group ID (RGID) or name. This selects the processes whose real group name or ID is in the grplist list. The real group ID identifies the group of the user who created the process, see getgid(2). -g grplist Select by session OR by effective group name. Selection by session is specified by many standards, but selection by effective group is the logical behavior that several other operating systems use. This ps will select by session when the list is completely numeric (as sessions are). Group ID numbers will work only when some group names are also specified. See the -s and --group options. --Group grplist Select by real group ID (RGID) or name. Identical to -G. --group grplist Select by effective group ID (EGID) or name. This selects the processes whose effective group name or ID is in grplist. The effective group ID describes the group whose file access permissions are used by the process (see getegid(2)). The -g option is often an alternative to --group. p pidlist Select by process ID. Identical to -p and --pid. -p pidlist Select by PID. This selects the processes whose process ID numbers appear in pidlist. Identical to p and --pid. --pid pidlist Select by process ID. Identical to -p and p. --ppid pidlist Select by parent process ID. This selects the processes with a parent process ID in pidlist. That is, it selects processes that are children of those listed in pidlist. q pidlist Select by process ID (quick mode). Identical to -q and --quick-pid. -q pidlist Select by PID (quick mode). This selects the processes whose process ID numbers appear in pidlist. With this option ps reads the necessary info only for the pids listed in the pidlist and doesn't apply additional filtering rules. The order of pids is unsorted and preserved. No additional selection options, sorting and forest type listings are allowed in this mode. Identical to q and --quick-pid. --quick-pid pidlist Select by process ID (quick mode). Identical to -q and q. -s sesslist Select by session ID. This selects the processes with a session ID specified in sesslist. --sid sesslist Select by session ID. Identical to -s. t ttylist Select by tty. Nearly identical to -t and --tty, but can also be used with an empty ttylist to indicate the terminal associated with ps. Using the T option is considered cleaner than using t with an empty ttylist. -t ttylist Select by tty. This selects the processes associated with the terminals given in ttylist. Terminals (ttys, or screens for text output) can be specified in several forms: /dev/ttyS1, ttyS1, S1. A plain "-" may be used to select processes not attached to any terminal. --tty ttylist Select by terminal. Identical to -t and t. U userlist Select by effective user ID (EUID) or name. This selects the processes whose effective user name or ID is in userlist. The effective user ID describes the user whose file access permissions are used by the process (see geteuid(2)). Identical to -u and --user. -U userlist Select by real user ID (RUID) or name. It selects the processes whose real user name or ID is in the userlist list. The real user ID identifies the user who created the process, see getuid(2). -u userlist Select by effective user ID (EUID) or name. This selects the processes whose effective user name or ID is in userlist. The effective user ID describes the user whose file access permissions are used by the process (see geteuid(2)). Identical to U and --user. --User userlist Select by real user ID (RUID) or name. Identical to -U. --user userlist Select by effective user ID (EUID) or name. Identical to -u and U. OUTPUT FORMAT CONTROL top These options are used to choose the information displayed by ps. The output may differ by personality. -c Show different scheduler information for the -l option. --context Display security context format (for SELinux). -f Do full-format listing. This option can be combined with many other UNIX-style options to add additional columns. It also causes the command arguments to be printed. When used with -L, the NLWP (number of threads) and LWP (thread ID) columns will be added. See the c option, the format keyword args, and the format keyword comm. -F Extra full format. See the -f option, which -F implies. --format format user-defined format. Identical to -o and o. j BSD job control format. -j Jobs format. l Display BSD long format. -l Long format. The -y option is often useful with this. -M Add a column of security data. Identical to Z (for SELinux). O format is preloaded o (overloaded). The BSD O option can act like -O (user-defined output format with some common fields predefined) or can be used to specify sort order. Heuristics are used to determine the behavior of this option. To ensure that the desired behavior is obtained (sorting or formatting), specify the option in some other way (e.g. with -O or --sort). When used as a formatting option, it is identical to -O, with the BSD personality. -O format Like -o, but preloaded with some default columns. Identical to -o pid,format,state,tname,time,command or -o pid,format,tname,time,cmd, see -o below. o format Specify user-defined format. Identical to -o and --format. -o format User-defined format. format is a single argument in the form of a blank-separated or comma-separated list, which offers a way to specify individual output columns. The recognized keywords are described in the STANDARD FORMAT SPECIFIERS section below. Headers may be renamed (ps -o pid,ruser=RealUser -o comm=Command) as desired. If all column headers are empty (ps -o pid= -o comm=) then the header line will not be output. Column width will increase as needed for wide headers; this may be used to widen up columns such as WCHAN (ps -o pid,wchan=WIDE- WCHAN-COLUMN -o comm). Explicit width control (ps opid, wchan:42,cmd) is offered too. The behavior of ps -o pid=X,comm=Y varies with personality; output may be one column named "X,comm=Y" or two columns named "X" and "Y". Use multiple -o options when in doubt. Use the PS_FORMAT environment variable to specify a default as desired; DefSysV and DefBSD are macros that may be used to choose the default UNIX or BSD columns. -P Add a column showing psr. s Display signal format. u Display user-oriented format. v Display virtual memory format. X Register format. -y Do not show flags; show rss in place of addr. This option can only be used with -l. Z Add a column of security data. Identical to -M (for SELinux). OUTPUT MODIFIERS top c Show the true command name. This is derived from the name of the executable file, rather than from the argv value. Command arguments and any modifications to them are thus not shown. This option effectively turns the args format keyword into the comm format keyword; it is useful with the -f format option and with the various BSD-style format options, which all normally display the command arguments. See the -f option, the format keyword args, and the format keyword comm. --cols n Set screen width. --columns n Set screen width. --cumulative Include some dead child process data (as a sum with the parent). -D format Set the date format of the lstart field to format. This format is parsed by strftime(3) and should be a maximum of 24 characters to not mis-align columns. --date-format format Identical to -D. e Show the environment after the command. f ASCII art process hierarchy (forest). --forest ASCII art process tree. h No header. (or, one header per screen in the BSD personality). The h option is problematic. Standard BSD ps uses this option to print a header on each page of output, but older Linux ps uses this option to totally disable the header. This version of ps follows the Linux usage of not printing the header unless the BSD personality has been selected, in which case it prints a header on each page of output. Regardless of the current personality, you can use the long options --headers and --no-headers to enable printing headers each page or disable headers entirely, respectively. -H Show process hierarchy (forest). --headers Repeat header lines, one per page of output. k spec Specify sorting order. Sorting syntax is [+|-]key[,[+|-]key[,...]]. Choose a multi-letter key from the STANDARD FORMAT SPECIFIERS section. The "+" is optional since default direction is increasing numerical or lexicographic order. Identical to --sort. Examples: ps jaxkuid,-ppid,+pid ps axk comm o comm,args ps kstart_time -ef --lines n Set screen height. n Numeric output for WCHAN and USER (including all types of UID and GID). --no-headers Print no header line at all. --no-heading is an alias for this option. O order Sorting order (overloaded). The BSD O option can act like -O (user-defined output format with some common fields predefined) or can be used to specify sort order. Heuristics are used to determine the behavior of this option. To ensure that the desired behavior is obtained (sorting or formatting), specify the option in some other way (e.g. with -O or --sort). For sorting, obsolete BSD O option syntax is O[+|-]k1[,[+|-]k2[,...]]. It orders the processes listing according to the multilevel sort specified by the sequence of one-letter short keys k1,k2, ... described in the OBSOLETE SORT KEYS section below. The "+" is currently optional, merely re-iterating the default direction on a key, but may help to distinguish an O sort from an O format. The "-" reverses direction only on the key it precedes. --rows n Set screen height. S Sum up some information, such as CPU usage, from dead child processes into their parent. This is useful for examining a system where a parent process repeatedly forks off short-lived children to do work. --sort spec Specify sorting order. Sorting syntax is [+|-]key[,[+|-]key[,...]]. Choose a multi-letter key from the STANDARD FORMAT SPECIFIERS section. The "+" is optional since default direction is increasing numerical or lexicographic order. Identical to k. For example: ps jax --sort=uid,-ppid,+pid --signames Show signal masks using abbreviated signal names and expands the collumn. If the column width cannot show all signals, the column will end with a plus "+". Columns with only a hyphen have no signals. w Wide output. Use this option twice for unlimited width. -w Wide output. Use this option twice for unlimited width. --width n Set screen width. THREAD DISPLAY top H Show threads as if they were processes. -L Show threads, possibly with LWP and NLWP columns. m Show threads after processes. -m Show threads after processes. -T Show threads, possibly with SPID column. OTHER INFORMATION top --help section Print a help message. The section argument can be one of simple, list, output, threads, misc, or all. The argument can be shortened to one of the underlined letters as in: s|l|o|t|m|a. --info Print debugging info. L List all format specifiers. V Print the procps-ng version. -V Print the procps-ng version. --version Print the procps-ng version. NOTES top This ps works by reading the virtual files in /proc. This ps does not need to be setuid kmem or have any privileges to run. Do not give this ps any special permissions. CPU usage is currently expressed as the percentage of time spent running during the entire lifetime of a process. This is not ideal, and it does not conform to the standards that ps otherwise conforms to. CPU usage is unlikely to add up to exactly 100%. The SIZE and RSS fields don't count some parts of a process including the page tables, kernel stack, struct thread_info, and struct task_struct. This is usually at least 20 KiB of memory that is always resident. SIZE is the virtual size of the process (code+data+stack). Processes marked <defunct> are dead processes (so-called "zombies") that remain because their parent has not destroyed them properly. These processes will be destroyed by init(8) if the parent process exits. If the length of the username is greater than the width of the display column, the username will be truncated. See the -o and -O formatting options to customize length. Commands options such as ps -aux are not recommended as it is a confusion of two different standards. According to the POSIX and UNIX standards, the above command asks to display all processes with a TTY (generally the commands users are running) plus all processes owned by a user named x. If that user doesn't exist, then ps will assume you really meant "ps aux". PROCESS FLAGS top The sum of these values is displayed in the "F" column, which is provided by the flags output specifier: 1 forked but didn't exec 4 used super-user privileges PROCESS STATE CODES top Here are the different values that the s, stat and state output specifiers (header "STAT" or "S") will display to describe the state of a process: D uninterruptible sleep (usually IO) I Idle kernel thread R running or runnable (on run queue) S interruptible sleep (waiting for an event to complete) T stopped by job control signal t stopped by debugger during the tracing W paging (not valid since the 2.6.xx kernel) X dead (should never be seen) Z defunct ("zombie") process, terminated but not reaped by its parent For BSD formats and when the stat keyword is used, additional characters may be displayed: < high-priority (not nice to other users) N low-priority (nice to other users) L has pages locked into memory (for real-time and custom IO) s is a session leader l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do) + is in the foreground process group OBSOLETE SORT KEYS top These keys are used by the BSD O option (when it is used for sorting). The GNU --sort option doesn't use these keys, but the specifiers described below in the STANDARD FORMAT SPECIFIERS section. Note that the values used in sorting are the internal values ps uses and not the "cooked" values used in some of the output format fields (e.g. sorting on tty will sort into device number, not according to the terminal name displayed). Pipe ps output into the sort(1) command if you want to sort the cooked values. KEY LONG DESCRIPTION c cmd simple name of executable C pcpu cpu utilization f flags flags as in long format F field g pgrp process group ID G tpgid controlling tty process group ID j cutime cumulative user time J cstime cumulative system time k utime user time m min_flt number of minor page faults M maj_flt number of major page faults n cmin_flt cumulative minor page faults N cmaj_flt cumulative major page faults o session session ID p pid process ID P ppid parent process ID r rss resident set size R resident resident pages s size memory size in kilobytes S share amount of shared pages t tty the device number of the controlling tty T start_time time process was started U uid user ID number u user user name v vsize total VM size in KiB y priority kernel scheduling priority AIX FORMAT DESCRIPTORS top This ps supports AIX format descriptors, which work somewhat like the formatting codes of printf(1) and printf(3). The NORMAL codes are described in the next section. CODE NORMAL HEADER %C pcpu %CPU %G group GROUP %P ppid PPID %U user USER %a args COMMAND %c comm COMMAND %g rgroup RGROUP %n nice NI %p pid PID %r pgid PGID %t etime ELAPSED %u ruser RUSER %x time TIME %y tty TTY %z vsz VSZ STANDARD FORMAT SPECIFIERS top Here are the different keywords that may be used to control the output format (e.g., with option -o) or to sort the selected processes with the GNU-style --sort option. For example: ps -eo pid,user,args --sort user This version of ps tries to recognize most of the keywords used in other implementations of ps. The following user-defined format specifiers may contain spaces: args, cmd, comm, command, fname, ucmd, ucomm, lstart, bsdstart, start. Some keywords may not be available for sorting. CODE HEADER DESCRIPTION %cpu %CPU cpu utilization of the process in "##.#" format. Currently, it is the CPU time used divided by the time the process has been running (cputime/realtime ratio), expressed as a percentage. It will not add up to 100% unless you are lucky. (alias pcpu). %mem %MEM ratio of the process's resident set size to the physical memory on the machine, expressed as a percentage. (alias pmem). ag_id AGID The autogroup identifier associated with a process which operates in conjunction with the CFS scheduler to improve interactive desktop performance. ag_nice AGNI The autogroup nice value which affects scheduling of all processes in that group. args COMMAND command with all its arguments as a string. Modifications to the arguments may be shown. The output in this column may contain spaces. A process marked <defunct> is partly dead, waiting to be fully destroyed by its parent. Sometimes the process args will be unavailable; when this happens, ps will instead print the executable name in brackets. (alias cmd, command). See also the comm format keyword, the -f option, and the c option. When specified last, this column will extend to the edge of the display. If ps can not determine display width, as when output is redirected (piped) into a file or another command, the output width is undefined (it may be 80, unlimited, determined by the TERM variable, and so on). The COLUMNS environment variable or --cols option may be used to exactly determine the width in this case. The w or -w option may be also be used to adjust width. blocked BLOCKED mask of the blocked signals, see signal(7). According to the width of the field, a 32 or 64-bit mask in hexadecimal format is displayed, unless the --signames option is used. (alias sig_block, sigmask). bsdstart START time the command started. If the process was started less than 24 hours ago, the output format is " HH:MM", else it is " Mmm:SS" (where Mmm is the three letters of the month). See also lstart, start, start_time, and stime. bsdtime TIME accumulated cpu time, user + system. The display format is usually "MMM:SS", but can be shifted to the right if the process used more than 999 minutes of cpu time. c C processor utilization. Currently, this is the integer value of the percent usage over the lifetime of the process. (see %cpu). caught CAUGHT mask of the caught signals, see signal(7). According to the width of the field, a 32 or 64 bits mask in hexadecimal format is displayed, unless the --signames option is used. (alias sig_catch, sigcatch). cgname CGNAME display name of control groups to which the process belongs. cgroup CGROUP display control groups to which the process belongs. cgroupns CGROUPNSUnique inode number describing the namespace the process belongs to. See namespaces(7). class CLS scheduling class of the process. (alias policy, cls). Field's possible values are: - not reported TS SCHED_OTHER FF SCHED_FIFO RR SCHED_RR B SCHED_BATCH ISO SCHED_ISO IDL SCHED_IDLE DLN SCHED_DEADLINE ? unknown value cls CLS scheduling class of the process. (alias policy, cls). Field's possible values are: - not reported TS SCHED_OTHER FF SCHED_FIFO RR SCHED_RR B SCHED_BATCH ISO SCHED_ISO IDL SCHED_IDLE DLN SCHED_DEADLINE ? unknown value cmd CMD see args. (alias args, command). comm COMMAND command name (only the executable name). The output in this column may contain spaces. (alias ucmd, ucomm). See also the args format keyword, the -f option, and the c option. When specified last, this column will extend to the edge of the display. If ps can not determine display width, as when output is redirected (piped) into a file or another command, the output width is undefined (it may be 80, unlimited, determined by the TERM variable, and so on). The COLUMNS environment variable or --cols option may be used to exactly determine the width in this case. The w or -w option may be also be used to adjust width. command COMMAND See args. (alias args, command). cp CP per-mill (tenths of a percent) CPU usage. (see %cpu). cputime TIME cumulative CPU time, "[DD-]hh:mm:ss" format. (alias time). cputimes TIME cumulative CPU time in seconds (alias times). cuc %CUC The CPU utilization of a process, including dead children, in an extended "##.###" format. (see also %cpu, c, cp, cuu, pcpu). cuu %CUU The CPU utilization of a process in an extended "##.###" format. (see also %cpu, c, cp, cuc, pcpu). drs DRS data resident set size, the amount of private memory reserved by a process. It is also known as DATA. Such memory may not yet be mapped to rss but will always be included included in the vsz amount. egid EGID effective group ID number of the process as a decimal integer. (alias gid). egroup EGROUP effective group ID of the process. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. (alias group). eip EIP instruction pointer. As of kernel 4.9.xx will be zeroed out unless task is exiting or being core dumped. esp ESP stack pointer. As of kernel 4.9.xx will be zeroed out unless task is exiting or being core dumped. etime ELAPSED elapsed time since the process was started, in the form [[DD-]hh:]mm:ss. etimes ELAPSED elapsed time since the process was started, in seconds. environ ENVIRON T{ environment variables for the process. T} euid EUID effective user ID (alias uid). euser EUSER effective user name. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. The n option can be used to force the decimal representation. (alias uname, user). exe EXE path to the executable. Useful if path cannot be printed via cmd, comm or args format options. f F flags associated with the process, see the PROCESS FLAGS section. (alias flag, flags). fgid FGID filesystem access group ID. (alias fsgid). fgroup FGROUP filesystem access group ID. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. (alias fsgroup). flag F see f. (alias f, flags). flags F see f. (alias f, flag). fname COMMAND first 8 bytes of the base name of the process's executable file. The output in this column may contain spaces. fuid FUID filesystem access user ID. (alias fsuid). fuser FUSER filesystem access user ID. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. gid GID see egid. (alias egid). group GROUP see egroup. (alias egroup). ignored IGNORED mask of the ignored signals, see signal(7). According to the width of the field, a 32 or 64 bits mask in hexadecimal format is displayed, unless the --signames option is used. (alias sig_ignore, sigignore). ipcns IPCNS Unique inode number describing the namespace the process belongs to. See namespaces(7). label LABEL security label, most commonly used for SELinux context data. This is for the Mandatory Access Control ("MAC") found on high-security systems. lstart STARTED time the command started. This will be in the form "DDD mmm HH:MM:SS YYY" unless changed by the -D option. lsession SESSION displays the login session identifier of a process, if systemd support has been included. luid LUID displays Login ID associated with a process. lwp LWP light weight process (thread) ID of the dispatchable entity (alias spid, tid). See tid for additional information. lxc LXC The name of the lxc container within which a task is running. If a process is not running inside a container, a dash ('-') will be shown. machine MACHINE displays the machine name for processes assigned to VM or container, if systemd support has been included. maj_flt MAJFLT The number of major page faults that have occurred with this process. min_flt MINFLT The number of minor page faults that have occurred with this process. mntns MNTNS Unique inode number describing the namespace the process belongs to. See namespaces(7). netns NETNS Unique inode number describing the namespace the process belongs to. See namespaces(7). ni NI nice value. This ranges from 19 (nicest) to -20 (not nice to others), see nice(1). (alias nice). nice NI see ni.(alias ni). nlwp NLWP number of lwps (threads) in the process. (alias thcount). numa NUMA The node associated with the most recently used processor. A -1 means that NUMA information is unavailable. nwchan WCHAN address of the kernel function where the process is sleeping (use wchan if you want the kernel function name). oom OOM Out of Memory Score. The value, ranging from 0 to +1000, used to select task(s) to kill when memory is exhausted. oomadj OOMADJ Out of Memory Adjustment Factor. The value is added to the current out of memory score which is then used to determine which task to kill when memory is exhausted. ouid OWNER displays the Unix user identifier of the owner of the session of a process, if systemd support has been included. pcpu %CPU see %cpu. (alias %cpu). pending PENDING mask of the pending signals. See signal(7). Signals pending on the process are distinct from signals pending on individual threads. Use the m option or the -m option to see both. According to the width of the field, a 32 or 64 bits mask in hexadecimal format is displayed, unless the --signames option is used. (alias sig). pgid PGID process group ID or, equivalently, the process ID of the process group leader. (alias pgrp). pgrp PGRP see pgid. (alias pgid). pid PID a number representing the process ID (alias tgid). pidns PIDNS Unique inode number describing the namespace the process belongs to. See namespaces(7). pmem %MEM see %mem. (alias %mem). policy POL scheduling class of the process. (alias class, cls). Possible values are: - not reported TS SCHED_OTHER FF SCHED_FIFO RR SCHED_RR B SCHED_BATCH ISO SCHED_ISO IDL SCHED_IDLE DLN SCHED_DEADLINE ? unknown value ppid PPID parent process ID. pri PRI priority of the process. Higher number means higher priority. psr PSR processor that process last executed on. pss PSS Proportional share size, the non-swapped physical memory, with shared memory proportionally accounted to all tasks mapping it. rbytes RBYTES Number of bytes which this process really did cause to be fetched from the storage layer. rchars RCHARS Number of bytes which this task has caused to be read from storage. rgid RGID real group ID. rgroup RGROUP real group name. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. rops ROPS Number of read I/O operationsthat is, system calls such as read(2) and pread(2). rss RSS resident set size, the non-swapped physical memory that a task has used (in kilobytes). (alias rssize, rsz). rssize RSS see rss. (alias rss, rsz). rsz RSZ see rss. (alias rss, rssize). rtprio RTPRIO realtime priority. ruid RUID real user ID. ruser RUSER real user ID. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. s S minimal state display (one character). See section PROCESS STATE CODES for the different values. See also stat if you want additional information displayed. (alias state). sched SCH scheduling policy of the process. The policies SCHED_OTHER (SCHED_NORMAL), SCHED_FIFO, SCHED_RR, SCHED_BATCH, SCHED_ISO, SCHED_IDLE and SCHED_DEADLINE are respectively displayed as 0, 1, 2, 3, 4, 5 and 6. seat SEAT displays the identifier associated with all hardware devices assigned to a specific workplace, if systemd support has been included. sess SESS session ID or, equivalently, the process ID of the session leader. (alias session, sid). sgi_p P processor that the process is currently executing on. Displays "*" if the process is not currently running or runnable. sgid SGID saved group ID. (alias svgid). sgroup SGROUP saved group name. This will be the textual group ID, if it can be obtained and the field width permits, or a decimal representation otherwise. sid SID see sess. (alias sess, session). sig PENDING see pending. (alias pending, sig_pend). sigcatch CAUGHT see caught. (alias caught, sig_catch). sigignore IGNORED see ignored. (alias ignored, sig_ignore). sigmask BLOCKED see blocked. (alias blocked, sig_block). size SIZE approximate amount of swap space that would be required if the process were to dirty all writable pages and then be swapped out. This number is very rough! slice SLICE displays the slice unit which a process belongs to, if systemd support has been included. spid SPID see lwp. (alias lwp, tid). stackp STACKP address of the bottom (start) of stack for the process. start STARTED time the command started. If the process was started less than 24 hours ago, the output format is "HH:MM:SS", else it is " Mmm dd" (where Mmm is a three-letter month name). See also bsdstart, start, start_time, and stime. start_time START starting time or date of the process. Only the year will be displayed if the process was not started the same year ps was invoked, or "MmmDD" if it was not started the same day, or "HH:MM" otherwise. See also bsdstart, start, lstart, and stime. stat STAT multi-character process state. See section PROCESS STATE CODES for the different values meaning. See also s and state if you just want the first character displayed. state S see s. (alias s). stime STIME see start_time. (alias start_time). suid SUID saved user ID. (alias svuid). supgid SUPGID group ids of supplementary groups, if any. See getgroups(2). supgrp SUPGRP group names of supplementary groups, if any. See getgroups(2). suser SUSER saved user name. This will be the textual user ID, if it can be obtained and the field width permits, or a decimal representation otherwise. (alias svuser). svgid SVGID see sgid. (alias sgid). svuid SVUID see suid. (alias suid). sz SZ size in physical pages of the core image of the process. This includes text, data, and stack space. Device mappings are currently excluded; this is subject to change. See vsz and rss. tgid TGID a number representing the thread group to which a task belongs (alias pid). It is the process ID of the thread group leader. thcount THCNT see nlwp. (alias nlwp). number of kernel threads owned by the process. tid TID the unique number representing a dispatchable entity (alias spid, tid). This value may also appear as: a process ID (pid); a process group ID (pgrp); a session ID for the session leader (sid); a thread group ID for the thread group leader (tgid); and a tty process group ID for the process group leader (tpgid). time TIME cumulative CPU time, "[DD-]HH:MM:SS" format. (alias cputime). timens TIMENS Unique inode number describing the namespace the process belongs to. See namespaces(7). times TIME cumulative CPU time in seconds (alias cputimes). tname TTY controlling tty (terminal). (alias tt, tty). tpgid TPGID ID of the foreground process group on the tty (terminal) that the process is connected to, or -1 if the process is not connected to a tty. trs TRS text resident set size, the amount of physical memory devoted to executable code. tt TT controlling tty (terminal). (alias tname, tty). tty TT controlling tty (terminal). (alias tname, tt). ucmd CMD see comm. (alias comm, ucomm). ucomm COMMAND see comm. (alias comm, ucmd). uid UID see euid. (alias euid). uname USER see euser. (alias euser, user). unit UNIT displays unit which a process belongs to, if systemd support has been included. user USER see euser. (alias euser, uname). userns USERNS Unique inode number describing the namespace the process belongs to. See namespaces(7). uss USS Unique set size, the non-swapped physical memory, which is not shared with an another task. utsns UTSNS Unique inode number describing the namespace the process belongs to. See namespaces(7). uunit UUNIT displays user unit which a process belongs to, if systemd support has been included. vsize VSZ see vsz. (alias vsz). vsz VSZ virtual memory size of the process in KiB (1024-byte units). Device mappings are currently excluded; this is subject to change. (alias vsize). wbytes WBYTES Number of bytes which this process caused to be sent to the storage layer. wcbytes WCBYTES Number of cancelled write bytes. wchan WCHAN name of the kernel function in which the process is sleeping. wchars WCHARS Number of bytes which this task has caused, or shall cause to be written to disk. wops WOPS Number of write I/O operationsthat is, system calls such as write(2) and pwrite(2). ENVIRONMENT VARIABLES top The following environment variables could affect ps: COLUMNS Override default display width. LINES Override default display height. PS_PERSONALITY Set to one of posix, old, linux, bsd, sun, digital... (see section PERSONALITY below). CMD_ENV Set to one of posix, old, linux, bsd, sun, digital... (see section PERSONALITY below). I_WANT_A_BROKEN_PS Force obsolete command line interpretation. LC_TIME Date format. LIBPROC_HIDE_KERNEL Set this to any value to hide kernel threads normally displayed with the -e option. This is equivalent to selecting --ppid 2 -p 2 --deselect instead. Also works in BSD mode. PS_COLORS Not currently supported. PS_FORMAT Default output format override. You may set this to a format string of the type used for the -o option. The DefSysV and DefBSD values are particularly useful. POSIXLY_CORRECT Don't find excuses to ignore bad "features". POSIX2 When set to "on", acts as POSIXLY_CORRECT. UNIX95 Don't find excuses to ignore bad "features". _XPG Cancel CMD_ENV=irix non-standard behavior. In general, it is a bad idea to set these variables. The one exception is CMD_ENV or PS_PERSONALITY, which could be set to Linux for normal systems. Without that setting, ps follows the useless and bad parts of the Unix98 standard. PERSONALITY top 390 like the OS/390 OpenEdition ps aix like AIX ps bsd like FreeBSD ps (totally non-standard) compaq like Digital Unix ps debian like the old Debian ps digital like Tru64 (was Digital Unix, was OSF/1) ps gnu like the old Debian ps hp like HP-UX ps hpux like HP-UX ps irix like Irix ps linux ***** recommended ***** old like the original Linux ps (totally non-standard) os390 like OS/390 Open Edition ps posix standard s390 like OS/390 Open Edition ps sco like SCO ps sgi like Irix ps solaris2 like Solaris 2+ (SunOS 5) ps sunos4 like SunOS 4 (Solaris 1) ps (totally non-standard) svr4 standard sysv standard tru64 like Tru64 (was Digital Unix, was OSF/1) ps unix standard unix95 standard unix98 standard BUGS top The fields bsdstart and start will only show the abbreviated month name in English. The fields lstart and stime will show the abbreviated month name in the configured locale but may exceed the column width due to the different lengths for abbreviated month and day names across languages. SEE ALSO top pgrep(1), pstree(1), top(1), strftime(3), proc(5). STANDARDS top This ps conforms to: 1 Version 2 of the Single Unix Specification 2 The Open Group Technical Standard Base Specifications, Issue 6 3 IEEE Std 1003.1, 2004 Edition 4 X/Open System Interfaces Extension [UP XSI] 5 ISO/IEC 9945:2003 AUTHOR top ps was originally written by Branko Lankester lankeste@fwi.uva. nl. Michael K. Johnson johnsonm@redhat.com re-wrote it significantly to use the proc filesystem, changing a few things in the process. Michael Shields mjshield@nyx.cs.du.edu added the pid-list feature. Charles Blake cblake@bbn.com added multi-level sorting, the dirent-style library, the device name-to-number mmaped database, the approximate binary search directly on System.map, and many code and documentation cleanups. David Mossberger-Tang wrote the generic BFD support for psupdate. Albert Cahalan albert@users.sf.net rewrote ps for full Unix98 and BSD support, along with some ugly hacks for obsolete and foreign syntax. Please send bug reports to procps@freelists.org. No subscription is required or suggested. COLOPHON top This page is part of the procps-ng (/proc filesystem utilities) project. Information about the project can be found at https://gitlab.com/procps-ng/procps. If you have a bug report for this manual page, see https://gitlab.com/procps-ng/procps/blob/master/Documentation/bugs.md. This page was obtained from the project's upstream Git repository https://gitlab.com/procps-ng/procps.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-10-16.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org procps-ng 2023-10-04 PS(1) Pages that refer to this page: free(1), fuser(1), htop(1), killall(1), pcp-ps(1), pgrep(1), pidstat(1), pmap(1), pmsleep(1), pslog(1), pstree(1), pwdx(1), slabtop(1), systemd(1), systemd-cgls(1), systemd-firstboot(1), systemd-nspawn(1), tcpdump(1), tload(1), top(1), uptime(1), w(1), proc(5), credentials(7), pid_namespaces(7), pthreads(7), sched(7), lsof(8), systemd-machined.service(8), tcpdump(8), vmstat(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. awk(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training awk(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT AWK(1P) POSIX Programmer's Manual AWK(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top awk pattern scanning and processing language SYNOPSIS top awk [-F sepstring] [-v assignment]... program [argument...] awk [-F sepstring] -f progfile [-f progfile]... [-v assignment]... [argument...] DESCRIPTION top The awk utility shall execute programs written in the awk programming language, which is specialized for textual data manipulation. An awk program is a sequence of patterns and corresponding actions. When input is read that matches a pattern, the action associated with that pattern is carried out. Input shall be interpreted as a sequence of records. By default, a record is a line, less its terminating <newline>, but this can be changed by using the RS built-in variable. Each record of input shall be matched in turn against each pattern in the program. For each pattern matched, the associated action shall be executed. The awk utility shall interpret each input record as a sequence of fields where, by default, a field is a string of non-<blank> non-<newline> characters. This default <blank> and <newline> field delimiter can be changed by using the FS built-in variable or the -F sepstring option. The awk utility shall denote the first field in a record $1, the second $2, and so on. The symbol $0 shall refer to the entire record; setting any other field causes the re-evaluation of $0. Assigning to $0 shall reset the values of all other fields and the NF built-in variable. OPTIONS top The awk utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported: -F sepstring Define the input field separator. This option shall be equivalent to: -v FS=sepstring except that if -F sepstring and -v FS=sepstring are both used, it is unspecified whether the FS assignment resulting from -F sepstring is processed in command line order or is processed after the last -v FS=sepstring. See the description of the FS built-in variable, and how it is used, in the EXTENDED DESCRIPTION section. -f progfile Specify the pathname of the file progfile containing an awk program. A pathname of '-' shall denote the standard input. If multiple instances of this option are specified, the concatenation of the files specified as progfile in the order specified shall be the awk program. The awk program can alternatively be specified in the command line as a single argument. -v assignment The application shall ensure that the assignment argument is in the same form as an assignment operand. The specified variable assignment shall occur prior to executing the awk program, including the actions associated with BEGIN patterns (if any). Multiple occurrences of this option can be specified. OPERANDS top The following operands shall be supported: program If no -f option is specified, the first operand to awk shall be the text of the awk program. The application shall supply the program operand as a single argument to awk. If the text does not end in a <newline>, awk shall interpret the text as if it did. argument Either of the following two types of argument can be intermixed: file A pathname of a file that contains the input to be read, which is matched against the set of patterns in the program. If no file operands are specified, or if a file operand is '-', the standard input shall be used. assignment An operand that begins with an <underscore> or alphabetic character from the portable character set (see the table in the Base Definitions volume of POSIX.12017, Section 6.1, Portable Character Set), followed by a sequence of underscores, digits, and alphabetics from the portable character set, followed by the '=' character, shall specify a variable assignment rather than a pathname. The characters before the '=' represent the name of an awk variable; if that name is an awk reserved word (see Grammar) the behavior is undefined. The characters following the <equals-sign> shall be interpreted as if they appeared in the awk program preceded and followed by a double-quote ('"') character, as a STRING token (see Grammar), except that if the last character is an unescaped <backslash>, it shall be interpreted as a literal <backslash> rather than as the first character of the sequence "\"". The variable shall be assigned the value of that STRING token and, if appropriate, shall be considered a numeric string (see Expressions in awk), the variable shall also be assigned its numeric value. Each such variable assignment shall occur just prior to the processing of the following file, if any. Thus, an assignment before the first file argument shall be executed after the BEGIN actions (if any), while an assignment after the last file argument shall occur before the END actions (if any). If there are no file arguments, assignments shall be executed before processing the standard input. STDIN top The standard input shall be used only if no file operands are specified, or if a file operand is '-', or if a progfile option- argument is '-'; see the INPUT FILES section. If the awk program contains no actions and no patterns, but is otherwise a valid awk program, standard input and any file operands shall not be read and awk shall exit with a return status of zero. INPUT FILES top Input files to the awk program from any of the following sources shall be text files: * Any file operands or their equivalents, achieved by modifying the awk variables ARGV and ARGC * Standard input in the absence of any file operands * Arguments to the getline function Whether the variable RS is set to a value other than a <newline> or not, for these files, implementations shall support records terminated with the specified separator up to {LINE_MAX} bytes and may support longer records. If -f progfile is specified, the application shall ensure that the files named by each of the progfile option-arguments are text files and their concatenation, in the same order as they appear in the arguments, is an awk program. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of awk: LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE Determine the locale for the behavior of ranges, equivalence classes, and multi-character collating elements within regular expressions and in comparisons of string values. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments and input files), the behavior of character classes within regular expressions, the identification of characters as letters, and the mapping of uppercase and lowercase characters for the toupper and tolower functions. LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. LC_NUMERIC Determine the radix character used when interpreting numeric input, performing conversions between numeric and string values, and formatting numeric output. Regardless of locale, the <period> character (the decimal-point character of the POSIX locale) is the decimal-point character recognized in processing awk programs (including assignments in command line arguments). NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. PATH Determine the search path when looking for commands executed by system(expr), or input and output pipes; see the Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables. In addition, all environment variables shall be visible via the awk variable ENVIRON. ASYNCHRONOUS EVENTS top Default. STDOUT top The nature of the output files depends on the awk program. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top The nature of the output files depends on the awk program. EXTENDED DESCRIPTION top Overall Program Structure An awk program is composed of pairs of the form: pattern { action } Either the pattern or the action (including the enclosing brace characters) can be omitted. A missing pattern shall match any record of input, and a missing action shall be equivalent to: { print } Execution of the awk program shall start by first executing the actions associated with all BEGIN patterns in the order they occur in the program. Then each file operand (or standard input if no files were specified) shall be processed in turn by reading data from the file until a record separator is seen (<newline> by default). Before the first reference to a field in the record is evaluated, the record shall be split into fields, according to the rules in Regular Expressions, using the value of FS that was current at the time the record was read. Each pattern in the program then shall be evaluated in the order of occurrence, and the action associated with each pattern that matches the current record executed. The action for a matching pattern shall be executed before evaluating subsequent patterns. Finally, the actions associated with all END patterns shall be executed in the order they occur in the program. Expressions in awk Expressions describe computations used in patterns and actions. In the following table, valid expression operations are given in groups from highest precedence first to lowest precedence last, with equal-precedence operators grouped between horizontal lines. In expression evaluation, where the grammar is formally ambiguous, higher precedence operators shall be evaluated before lower precedence operators. In this table expr, expr1, expr2, and expr3 represent any expression, while lvalue represents any entity that can be assigned to (that is, on the left side of an assignment operator). The precise syntax of expressions is given in Grammar. Table 4-1: Expressions in Decreasing Precedence in awk Syntax Name Type of Result Associativity ( expr ) Grouping Type of expr N/A $expr Field reference String N/A lvalue ++ Post-increment Numeric N/A lvalue -- Post-decrement Numeric N/A ++ lvalue Pre-increment Numeric N/A -- lvalue Pre-decrement Numeric N/A expr ^ expr Exponentiation Numeric Right ! expr Logical not Numeric N/A + expr Unary plus Numeric N/A - expr Unary minus Numeric N/A expr * expr Multiplication Numeric Left expr / expr Division Numeric Left expr % expr Modulus Numeric Left expr + expr Addition Numeric Left expr - expr Subtraction Numeric Left expr expr String concatenation String Left expr < expr Less than Numeric None expr <= expr Less than or equal to Numeric None expr != expr Not equal to Numeric None expr == expr Equal to Numeric None expr > expr Greater than Numeric None expr >= expr Greater than or equal to Numeric None expr ~ expr ERE match Numeric None expr !~ expr ERE non-match Numeric None expr in array Array membership Numeric Left ( index ) in array Multi-dimension array Numeric Left membership expr && expr Logical AND Numeric Left expr || expr Logical OR Numeric Left expr1 ? expr2 : expr3Conditional expression Type of selectedRight expr2 or expr3 lvalue ^= expr Exponentiation assignmentNumeric Right lvalue %= expr Modulus assignment Numeric Right lvalue *= expr Multiplication assignmentNumeric Right lvalue /= expr Division assignment Numeric Right lvalue += expr Addition assignment Numeric Right lvalue -= expr Subtraction assignment Numeric Right lvalue = expr Assignment Type of expr Right Each expression shall have either a string value, a numeric value, or both. Except as stated for specific contexts, the value of an expression shall be implicitly converted to the type needed for the context in which it is used. A string value shall be converted to a numeric value either by the equivalent of the following calls to functions defined by the ISO C standard: setlocale(LC_NUMERIC, ""); numeric_value = atof(string_value); or by converting the initial portion of the string to type double representation as follows: The input string is decomposed into two parts: an initial, possibly empty, sequence of white-space characters (as specified by isspace()) and a subject sequence interpreted as a floating-point constant. The expected form of the subject sequence is an optional '+' or '-' sign, then a non-empty sequence of digits optionally containing a <period>, then an optional exponent part. An exponent part consists of 'e' or 'E', followed by an optional sign, followed by one or more decimal digits. The sequence starting with the first digit or the <period> (whichever occurs first) is interpreted as a floating constant of the C language, and if neither an exponent part nor a <period> appears, a <period> is assumed to follow the last digit in the string. If the subject sequence begins with a <hyphen-minus>, the value resulting from the conversion is negated. A numeric value that is exactly equal to the value of an integer (see Section 1.1.2, Concepts Derived from the ISO C Standard) shall be converted to a string by the equivalent of a call to the sprintf function (see String Functions) with the string "%d" as the fmt argument and the numeric value being converted as the first and only expr argument. Any other numeric value shall be converted to a string by the equivalent of a call to the sprintf function with the value of the variable CONVFMT as the fmt argument and the numeric value being converted as the first and only expr argument. The result of the conversion is unspecified if the value of CONVFMT is not a floating-point format specification. This volume of POSIX.12017 specifies no explicit conversions between numbers and strings. An application can force an expression to be treated as a number by adding zero to it, or can force it to be treated as a string by concatenating the null string ("") to it. A string value shall be considered a numeric string if it comes from one of the following: 1. Field variables 2. Input from the getline() function 3. FILENAME 4. ARGV array elements 5. ENVIRON array elements 6. Array elements created by the split() function 7. A command line variable assignment 8. Variable assignment from another numeric string variable and an implementation-dependent condition corresponding to either case (a) or (b) below is met. a. After the equivalent of the following calls to functions defined by the ISO C standard, string_value_end would differ from string_value, and any characters before the terminating null character in string_value_end would be <blank> characters: char *string_value_end; setlocale(LC_NUMERIC, ""); numeric_value = strtod (string_value, &string_value_end); b. After all the following conversions have been applied, the resulting string would lexically be recognized as a NUMBER token as described by the lexical conventions in Grammar: -- All leading and trailing <blank> characters are discarded. -- If the first non-<blank> is '+' or '-', it is discarded. -- Each occurrence of the decimal point character from the current locale is changed to a <period>. In case (a) the numeric value of the numeric string shall be the value that would be returned by the strtod() call. In case (b) if the first non-<blank> is '-', the numeric value of the numeric string shall be the negation of the numeric value of the recognized NUMBER token; otherwise, the numeric value of the numeric string shall be the numeric value of the recognized NUMBER token. Whether or not a string is a numeric string shall be relevant only in contexts where that term is used in this section. When an expression is used in a Boolean context, if it has a numeric value, a value of zero shall be treated as false and any other value shall be treated as true. Otherwise, a string value of the null string shall be treated as false and any other value shall be treated as true. A Boolean context shall be one of the following: * The first subexpression of a conditional expression * An expression operated on by logical NOT, logical AND, or logical OR * The second expression of a for statement * The expression of an if statement * The expression of the while clause in either a while or do...while statement * An expression used as a pattern (as in Overall Program Structure) All arithmetic shall follow the semantics of floating-point arithmetic as specified by the ISO C standard (see Section 1.1.2, Concepts Derived from the ISO C Standard). The value of the expression: expr1 ^ expr2 shall be equivalent to the value returned by the ISO C standard function call: pow(expr1, expr2) The expression: lvalue ^= expr shall be equivalent to the ISO C standard expression: lvalue = pow(lvalue, expr) except that lvalue shall be evaluated only once. The value of the expression: expr1 % expr2 shall be equivalent to the value returned by the ISO C standard function call: fmod(expr1, expr2) The expression: lvalue %= expr shall be equivalent to the ISO C standard expression: lvalue = fmod(lvalue, expr) except that lvalue shall be evaluated only once. Variables and fields shall be set by the assignment statement: lvalue = expression and the type of expression shall determine the resulting variable type. The assignment includes the arithmetic assignments ("+=", "-=", "*=", "/=", "%=", "^=", "++", "--") all of which shall produce a numeric result. The left-hand side of an assignment and the target of increment and decrement operators can be one of a variable, an array with index, or a field selector. The awk language supplies arrays that are used for storing numbers or strings. Arrays need not be declared. They shall initially be empty, and their sizes shall change dynamically. The subscripts, or element identifiers, are strings, providing a type of associative array capability. An array name followed by a subscript within square brackets can be used as an lvalue and thus as an expression, as described in the grammar; see Grammar. Unsubscripted array names can be used in only the following contexts: * A parameter in a function definition or function call * The NAME token following any use of the keyword in as specified in the grammar (see Grammar); if the name used in this context is not an array name, the behavior is undefined A valid array index shall consist of one or more <comma>-separated expressions, similar to the way in which multi- dimensional arrays are indexed in some programming languages. Because awk arrays are really one-dimensional, such a <comma>-separated list shall be converted to a single string by concatenating the string values of the separate expressions, each separated from the other by the value of the SUBSEP variable. Thus, the following two index operations shall be equivalent: var[expr1, expr2, ... exprn] var[expr1 SUBSEP expr2 SUBSEP ... SUBSEP exprn] The application shall ensure that a multi-dimensioned index used with the in operator is parenthesized. The in operator, which tests for the existence of a particular array element, shall not cause that element to exist. Any other reference to a nonexistent array element shall automatically create it. Comparisons (with the '<', "<=", "!=", "==", '>', and ">=" operators) shall be made numerically if both operands are numeric, if one is numeric and the other has a string value that is a numeric string, or if one is numeric and the other has the uninitialized value. Otherwise, operands shall be converted to strings as required and a string comparison shall be made as follows: * For the "!=" and "==" operators, the strings should be compared to check if they are identical but may be compared using the locale-specific collation sequence to check if they collate equally. * For the other operators, the strings shall be compared using the locale-specific collation sequence. The value of the comparison expression shall be 1 if the relation is true, or 0 if the relation is false. Variables and Special Variables Variables can be used in an awk program by referencing them. With the exception of function parameters (see User-Defined Functions), they are not explicitly declared. Function parameter names shall be local to the function; all other variable names shall be global. The same name shall not be used as both a function parameter name and as the name of a function or a special awk variable. The same name shall not be used both as a variable name with global scope and as the name of a function. The same name shall not be used within the same scope both as a scalar variable and as an array. Uninitialized variables, including scalar variables, array elements, and field variables, shall have an uninitialized value. An uninitialized value shall have both a numeric value of zero and a string value of the empty string. Evaluation of variables with an uninitialized value, to either string or numeric, shall be determined by the context in which they are used. Field variables shall be designated by a '$' followed by a number or numerical expression. The effect of the field number expression evaluating to anything other than a non-negative integer is unspecified; uninitialized variables or string values need not be converted to numeric values in this context. New field variables can be created by assigning a value to them. References to nonexistent fields (that is, fields after $NF), shall evaluate to the uninitialized value. Such references shall not create new fields. However, assigning to a nonexistent field (for example, $(NF+2)=5) shall increase the value of NF; create any intervening fields with the uninitialized value; and cause the value of $0 to be recomputed, with the fields being separated by the value of OFS. Each field variable shall have a string value or an uninitialized value when created. Field variables shall have the uninitialized value when created from $0 using FS and the variable does not contain any characters. If appropriate, the field variable shall be considered a numeric string (see Expressions in awk). Implementations shall support the following other special variables that are set by awk: ARGC The number of elements in the ARGV array. ARGV An array of command line arguments, excluding options and the program argument, numbered from zero to ARGC-1. The arguments in ARGV can be modified or added to; ARGC can be altered. As each input file ends, awk shall treat the next non-null element of ARGV, up to the current value of ARGC-1, inclusive, as the name of the next input file. Thus, setting an element of ARGV to null means that it shall not be treated as an input file. The name '-' indicates the standard input. If an argument matches the format of an assignment operand, this argument shall be treated as an assignment rather than a file argument. CONVFMT The printf format for converting numbers to strings (except for output statements, where OFMT is used); "%.6g" by default. ENVIRON An array representing the value of the environment, as described in the exec functions defined in the System Interfaces volume of POSIX.12017. The indices of the array shall be strings consisting of the names of the environment variables, and the value of each array element shall be a string consisting of the value of that variable. If appropriate, the environment variable shall be considered a numeric string (see Expressions in awk); the array element shall also have its numeric value. In all cases where the behavior of awk is affected by environment variables (including the environment of any commands that awk executes via the system function or via pipeline redirections with the print statement, the printf statement, or the getline function), the environment used shall be the environment at the time awk began executing; it is implementation-defined whether any modification of ENVIRON affects this environment. FILENAME A pathname of the current input file. Inside a BEGIN action the value is undefined. Inside an END action the value shall be the name of the last input file processed. FNR The ordinal number of the current record in the current file. Inside a BEGIN action the value shall be zero. Inside an END action the value shall be the number of the last record processed in the last file processed. FS Input field separator regular expression; a <space> by default. NF The number of fields in the current record. Inside a BEGIN action, the use of NF is undefined unless a getline function without a var argument is executed previously. Inside an END action, NF shall retain the value it had for the last record read, unless a subsequent, redirected, getline function without a var argument is performed prior to entering the END action. NR The ordinal number of the current record from the start of input. Inside a BEGIN action the value shall be zero. Inside an END action the value shall be the number of the last record processed. OFMT The printf format for converting numbers to strings in output statements (see Output Statements); "%.6g" by default. The result of the conversion is unspecified if the value of OFMT is not a floating-point format specification. OFS The print statement output field separator; <space> by default. ORS The print statement output record separator; a <newline> by default. RLENGTH The length of the string matched by the match function. RS The first character of the string value of RS shall be the input record separator; a <newline> by default. If RS contains more than one character, the results are unspecified. If RS is null, then records are separated by sequences consisting of a <newline> plus one or more blank lines, leading or trailing blank lines shall not result in empty records at the beginning or end of the input, and a <newline> shall always be a field separator, no matter what the value of FS is. RSTART The starting position of the string matched by the match function, numbering from 1. This shall always be equivalent to the return value of the match function. SUBSEP The subscript separator string for multi-dimensional arrays; the default value is implementation-defined. Regular Expressions The awk utility shall make use of the extended regular expression notation (see the Base Definitions volume of POSIX.12017, Section 9.4, Extended Regular Expressions) except that it shall allow the use of C-language conventions for escaping special characters within the EREs, as specified in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v') and the following table; these escape sequences shall be recognized both inside and outside bracket expressions. Note that records need not be separated by <newline> characters and string constants can contain <newline> characters, so even the "\n" sequence is valid in awk EREs. Using a <slash> character within an ERE requires the escaping shown in the following table. Table 4-2: Escape Sequences in awk Escape Sequence Description Meaning \" <backslash> <quotation-mark> <quotation-mark> character \/ <backslash> <slash> <slash> character \ddd A <backslash> character followed The character whose encoding is by the longest sequence of one, represented by the one, two, or two, or three octal-digit three-digit octal integer. Multi- characters (01234567). If all of byte characters require multiple, the digits are 0 (that is, concatenated escape sequences of representation of the NUL this type, including the leading character), the behavior is <backslash> for each byte. undefined. \c A <backslash> character followed Undefined by any character not described in this table or in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v'). A regular expression can be matched against a specific field or string by using one of the two regular expression matching operators, '~' and "!~". These operators shall interpret their right-hand operand as a regular expression and their left-hand operand as a string. If the regular expression matches the string, the '~' expression shall evaluate to a value of 1, and the "!~" expression shall evaluate to a value of 0. (The regular expression matching operation is as defined by the term matched in the Base Definitions volume of POSIX.12017, Section 9.1, Regular Expression Definitions, where a match occurs on any part of the string unless the regular expression is limited with the <circumflex> or <dollar-sign> special characters.) If the regular expression does not match the string, the '~' expression shall evaluate to a value of 0, and the "!~" expression shall evaluate to a value of 1. If the right-hand operand is any expression other than the lexical token ERE, the string value of the expression shall be interpreted as an extended regular expression, including the escape conventions described above. Note that these same escape conventions shall also be applied in determining the value of a string literal (the lexical token STRING), and thus shall be applied a second time when a string literal is used in this context. When an ERE token appears as an expression in any context other than as the right-hand of the '~' or "!~" operator or as one of the built-in function arguments described below, the value of the resulting expression shall be the equivalent of: $0 ~ /ere/ The ere argument to the gsub, match, sub functions, and the fs argument to the split function (see String Functions) shall be interpreted as extended regular expressions. These can be either ERE tokens or arbitrary expressions, and shall be interpreted in the same manner as the right-hand side of the '~' or "!~" operator. An extended regular expression can be used to separate fields by assigning a string containing the expression to the built-in variable FS, either directly or as a consequence of using the -F sepstring option. The default value of the FS variable shall be a single <space>. The following describes FS behavior: 1. If FS is a null string, the behavior is unspecified. 2. If FS is a single character: a. If FS is <space>, skip leading and trailing <blank> and <newline> characters; fields shall be delimited by sets of one or more <blank> or <newline> characters. b. Otherwise, if FS is any other character c, fields shall be delimited by each single occurrence of c. 3. Otherwise, the string value of FS shall be considered to be an extended regular expression. Each occurrence of a sequence matching the extended regular expression shall delimit fields. Except for the '~' and "!~" operators, and in the gsub, match, split, and sub built-in functions, ERE matching shall be based on input records; that is, record separator characters (the first character of the value of the variable RS, <newline> by default) cannot be embedded in the expression, and no expression shall match the record separator character. If the record separator is not <newline>, <newline> characters embedded in the expression can be matched. For the '~' and "!~" operators, and in those four built-in functions, ERE matching shall be based on text strings; that is, any character (including <newline> and the record separator) can be embedded in the pattern, and an appropriate pattern shall match any character. However, in all awk ERE matching, the use of one or more NUL characters in the pattern, input record, or text string produces undefined results. Patterns A pattern is any valid expression, a range specified by two expressions separated by a comma, or one of the two special patterns BEGIN or END. Special Patterns The awk utility shall recognize two special patterns, BEGIN and END. Each BEGIN pattern shall be matched once and its associated action executed before the first record of input is readexcept possibly by use of the getline function (see Input/Output and General Functions) in a prior BEGIN actionand before command line assignment is done. Each END pattern shall be matched once and its associated action executed after the last record of input has been read. These two patterns shall have associated actions. BEGIN and END shall not combine with other patterns. Multiple BEGIN and END patterns shall be allowed. The actions associated with the BEGIN patterns shall be executed in the order specified in the program, as are the END actions. An END pattern can precede a BEGIN pattern in a program. If an awk program consists of only actions with the pattern BEGIN, and the BEGIN action contains no getline function, awk shall exit without reading its input when the last statement in the last BEGIN action is executed. If an awk program consists of only actions with the pattern END or only actions with the patterns BEGIN and END, the input shall be read before the statements in the END actions are executed. Expression Patterns An expression pattern shall be evaluated as if it were an expression in a Boolean context. If the result is true, the pattern shall be considered to match, and the associated action (if any) shall be executed. If the result is false, the action shall not be executed. Pattern Ranges A pattern range consists of two expressions separated by a comma; in this case, the action shall be performed for all records between a match of the first expression and the following match of the second expression, inclusive. At this point, the pattern range can be repeated starting at input records subsequent to the end of the matched range. Actions An action is a sequence of statements as shown in the grammar in Grammar. Any single statement can be replaced by a statement list enclosed in curly braces. The application shall ensure that statements in a statement list are separated by <newline> or <semicolon> characters. Statements in a statement list shall be executed sequentially in the order that they appear. The expression acting as the conditional in an if statement shall be evaluated and if it is non-zero or non-null, the following statement shall be executed; otherwise, if else is present, the statement following the else shall be executed. The if, while, do...while, for, break, and continue statements are based on the ISO C standard (see Section 1.1.2, Concepts Derived from the ISO C Standard), except that the Boolean expressions shall be treated as described in Expressions in awk, and except in the case of: for (variable in array) which shall iterate, assigning each index of array to variable in an unspecified order. The results of adding new elements to array within such a for loop are undefined. If a break or continue statement occurs outside of a loop, the behavior is undefined. The delete statement shall remove an individual array element. Thus, the following code deletes an entire array: for (index in array) delete array[index] The next statement shall cause all further processing of the current input record to be abandoned. The behavior is undefined if a next statement appears or is invoked in a BEGIN or END action. The exit statement shall invoke all END actions in the order in which they occur in the program source and then terminate the program without reading further input. An exit statement inside an END action shall terminate the program without further execution of END actions. If an expression is specified in an exit statement, its numeric value shall be the exit status of awk, unless subsequent errors are encountered or a subsequent exit statement with an expression is executed. Output Statements Both print and printf statements shall write to standard output by default. The output shall be written to the location specified by output_redirection if one is supplied, as follows: > expression >> expression | expression In all cases, the expression shall be evaluated to produce a string that is used as a pathname into which to write (for '>' or ">>") or as a command to be executed (for '|'). Using the first two forms, if the file of that name is not currently open, it shall be opened, creating it if necessary and using the first form, truncating the file. The output then shall be appended to the file. As long as the file remains open, subsequent calls in which expression evaluates to the same string value shall simply append output to the file. The file remains open until the close function (see Input/Output and General Functions) is called with an expression that evaluates to the same string value. The third form shall write output onto a stream piped to the input of a command. The stream shall be created if no stream is currently open with the value of expression as its command name. The stream created shall be equivalent to one created by a call to the popen() function defined in the System Interfaces volume of POSIX.12017 with the value of expression as the command argument and a value of w as the mode argument. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value shall write output to the existing stream. The stream shall remain open until the close function (see Input/Output and General Functions) is called with an expression that evaluates to the same string value. At that time, the stream shall be closed as if by a call to the pclose() function defined in the System Interfaces volume of POSIX.12017. As described in detail by the grammar in Grammar, these output statements shall take a <comma>-separated list of expressions referred to in the grammar by the non-terminal symbols expr_list, print_expr_list, or print_expr_list_opt. This list is referred to here as the expression list, and each member is referred to as an expression argument. The print statement shall write the value of each expression argument onto the indicated output stream separated by the current output field separator (see variable OFS above), and terminated by the output record separator (see variable ORS above). All expression arguments shall be taken as strings, being converted if necessary; this conversion shall be as described in Expressions in awk, with the exception that the printf format in OFMT shall be used instead of the value in CONVFMT. An empty expression list shall stand for the whole input record ($0). The printf statement shall produce output based on a notation similar to the File Format Notation used to describe file formats in this volume of POSIX.12017 (see the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation). Output shall be produced as specified with the first expression argument as the string format and subsequent expression arguments as the strings arg1 to argn, inclusive, with the following exceptions: 1. The format shall be an actual character string rather than a graphical representation. Therefore, it cannot contain empty character positions. The <space> in the format string, in any context other than a flag of a conversion specification, shall be treated as an ordinary character that is copied to the output. 2. If the character set contains a '' character and that character appears in the format string, it shall be treated as an ordinary character that is copied to the output. 3. The escape sequences beginning with a <backslash> character shall be treated as sequences of ordinary characters that are copied to the output. Note that these same sequences shall be interpreted lexically by awk when they appear in literal strings, but they shall not be treated specially by the printf statement. 4. A field width or precision can be specified as the '*' character instead of a digit string. In this case the next argument from the expression list shall be fetched and its numeric value taken as the field width or precision. 5. The implementation shall not precede or follow output from the d or u conversion specifier characters with <blank> characters not specified by the format string. 6. The implementation shall not precede output from the o conversion specifier character with leading zeros not specified by the format string. 7. For the c conversion specifier character: if the argument has a numeric value, the character whose encoding is that value shall be output. If the value is zero or is not the encoding of any character in the character set, the behavior is undefined. If the argument does not have a numeric value, the first character of the string value shall be output; if the string does not contain any characters, the behavior is undefined. 8. For each conversion specification that consumes an argument, the next expression argument shall be evaluated. With the exception of the c conversion specifier character, the value shall be converted (according to the rules specified in Expressions in awk) to the appropriate type for the conversion specification. 9. If there are insufficient expression arguments to satisfy all the conversion specifications in the format string, the behavior is undefined. 10. If any character sequence in the format string begins with a '%' character, but does not form a valid conversion specification, the behavior is unspecified. Both print and printf can output at least {LINE_MAX} bytes. Functions The awk language has a variety of built-in functions: arithmetic, string, input/output, and general. Arithmetic Functions The arithmetic functions, except for int, shall be based on the ISO C standard (see Section 1.1.2, Concepts Derived from the ISO C Standard). The behavior is undefined in cases where the ISO C standard specifies that an error be returned or that the behavior is undefined. Although the grammar (see Grammar) permits built-in functions to appear with no arguments or parentheses, unless the argument or parentheses are indicated as optional in the following list (by displaying them within the "[]" brackets), such use is undefined. atan2(y,x) Return arctangent of y/x in radians in the range [-,]. cos(x) Return cosine of x, where x is in radians. sin(x) Return sine of x, where x is in radians. exp(x) Return the exponential function of x. log(x) Return the natural logarithm of x. sqrt(x) Return the square root of x. int(x) Return the argument truncated to an integer. Truncation shall be toward 0 when x>0. rand() Return a random number n, such that 0n<1. srand([expr]) Set the seed value for rand to expr or use the time of day if expr is omitted. The previous seed value shall be returned. String Functions The string functions in the following list shall be supported. Although the grammar (see Grammar) permits built-in functions to appear with no arguments or parentheses, unless the argument or parentheses are indicated as optional in the following list (by displaying them within the "[]" brackets), such use is undefined. gsub(ere, repl[, in]) Behave like sub (see below), except that it shall replace all occurrences of the regular expression (like the ed utility global substitute) in $0 or in the in argument, when specified. index(s, t) Return the position, in characters, numbering from 1, in string s where string t first occurs, or zero if it does not occur at all. length[([s])] Return the length, in characters, of its argument taken as a string, or of the whole record, $0, if there is no argument. match(s, ere) Return the position, in characters, numbering from 1, in string s where the extended regular expression ere occurs, or zero if it does not occur at all. RSTART shall be set to the starting position (which is the same as the returned value), zero if no match is found; RLENGTH shall be set to the length of the matched string, -1 if no match is found. split(s, a[, fs ]) Split the string s into array elements a[1], a[2], ..., a[n], and return n. All elements of the array shall be deleted before the split is performed. The separation shall be done with the ERE fs or with the field separator FS if fs is not given. Each array element shall have a string value when created and, if appropriate, the array element shall be considered a numeric string (see Expressions in awk). The effect of a null string as the value of fs is unspecified. sprintf(fmt, expr, expr, ...) Format the expressions according to the printf format given by fmt and return the resulting string. sub(ere, repl[, in ]) Substitute the string repl in place of the first instance of the extended regular expression ERE in string in and return the number of substitutions. An <ampersand> ('&') appearing in the string repl shall be replaced by the string from in that matches the ERE. An <ampersand> preceded with a <backslash> shall be interpreted as the literal <ampersand> character. An occurrence of two consecutive <backslash> characters shall be interpreted as just a single literal <backslash> character. Any other occurrence of a <backslash> (for example, preceding any other character) shall be treated as a literal <backslash> character. Note that if repl is a string literal (the lexical token STRING; see Grammar), the handling of the <ampersand> character occurs after any lexical processing, including any lexical <backslash>-escape sequence processing. If in is specified and it is not an lvalue (see Expressions in awk), the behavior is undefined. If in is omitted, awk shall use the current record ($0) in its place. substr(s, m[, n ]) Return the at most n-character substring of s that begins at position m, numbering from 1. If n is omitted, or if n specifies more characters than are left in the string, the length of the substring shall be limited by the length of the string s. tolower(s) Return a string based on the string s. Each character in s that is an uppercase letter specified to have a tolower mapping by the LC_CTYPE category of the current locale shall be replaced in the returned string by the lowercase letter specified by the mapping. Other characters in s shall be unchanged in the returned string. toupper(s) Return a string based on the string s. Each character in s that is a lowercase letter specified to have a toupper mapping by the LC_CTYPE category of the current locale is replaced in the returned string by the uppercase letter specified by the mapping. Other characters in s are unchanged in the returned string. All of the preceding functions that take ERE as a parameter expect a pattern or a string valued expression that is a regular expression as defined in Regular Expressions. Input/Output and General Functions The input/output and general functions are: close(expression) Close the file or pipe opened by a print or printf statement or a call to getline with the same string- valued expression. The limit on the number of open expression arguments is implementation-defined. If the close was successful, the function shall return zero; otherwise, it shall return non-zero. expression | getline [var] Read a record of input from a stream piped from the output of a command. The stream shall be created if no stream is currently open with the value of expression as its command name. The stream created shall be equivalent to one created by a call to the popen() function with the value of expression as the command argument and a value of r as the mode argument. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value shall read subsequent records from the stream. The stream shall remain open until the close function is called with an expression that evaluates to the same string value. At that time, the stream shall be closed as if by a call to the pclose() function. If var is omitted, $0 and NF shall be set; otherwise, var shall be set and, if appropriate, it shall be considered a numeric string (see Expressions in awk). The getline operator can form ambiguous constructs when there are unparenthesized operators (including concatenate) to the left of the '|' (to the beginning of the expression containing getline). In the context of the '$' operator, '|' shall behave as if it had a lower precedence than '$'. The result of evaluating other operators is unspecified, and conforming applications shall parenthesize properly all such usages. getline Set $0 to the next input record from the current input file. This form of getline shall set the NF, NR, and FNR variables. getline var Set variable var to the next input record from the current input file and, if appropriate, var shall be considered a numeric string (see Expressions in awk). This form of getline shall set the FNR and NR variables. getline [var] < expression Read the next record of input from a named file. The expression shall be evaluated to produce a string that is used as a pathname. If the file of that name is not currently open, it shall be opened. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value shall read subsequent records from the file. The file shall remain open until the close function is called with an expression that evaluates to the same string value. If var is omitted, $0 and NF shall be set; otherwise, var shall be set and, if appropriate, it shall be considered a numeric string (see Expressions in awk). The getline operator can form ambiguous constructs when there are unparenthesized binary operators (including concatenate) to the right of the '<' (up to the end of the expression containing the getline). The result of evaluating such a construct is unspecified, and conforming applications shall parenthesize properly all such usages. system(expression) Execute the command given by expression in a manner equivalent to the system() function defined in the System Interfaces volume of POSIX.12017 and return the exit status of the command. All forms of getline shall return 1 for successful input, zero for end-of-file, and -1 for an error. Where strings are used as the name of a file or pipeline, the application shall ensure that the strings are textually identical. The terminology ``same string value'' implies that ``equivalent strings'', even those that differ only by <space> characters, represent different files. User-Defined Functions The awk language also provides user-defined functions. Such functions can be defined as: function name([parameter, ...]) { statements } A function can be referred to anywhere in an awk program; in particular, its use can precede its definition. The scope of a function is global. Function parameters, if present, can be either scalars or arrays; the behavior is undefined if an array name is passed as a parameter that the function uses as a scalar, or if a scalar expression is passed as a parameter that the function uses as an array. Function parameters shall be passed by value if scalar and by reference if array name. The number of parameters in the function definition need not match the number of parameters in the function call. Excess formal parameters can be used as local variables. If fewer arguments are supplied in a function call than are in the function definition, the extra parameters that are used in the function body as scalars shall evaluate to the uninitialized value until they are otherwise initialized, and the extra parameters that are used in the function body as arrays shall be treated as uninitialized arrays where each element evaluates to the uninitialized value until otherwise initialized. When invoking a function, no white space can be placed between the function name and the opening parenthesis. Function calls can be nested and recursive calls can be made upon functions. Upon return from any nested or recursive function call, the values of all of the calling function's parameters shall be unchanged, except for array parameters passed by reference. The return statement can be used to return a value. If a return statement appears outside of a function definition, the behavior is undefined. In the function definition, <newline> characters shall be optional before the opening brace and after the closing brace. Function definitions can appear anywhere in the program where a pattern-action pair is allowed. Grammar The grammar in this section and the lexical conventions in the following section shall together describe the syntax for awk programs. The general conventions for this style of grammar are described in Section 1.3, Grammar Conventions. A valid program can be represented as the non-terminal symbol program in the grammar. This formal syntax shall take precedence over the preceding text syntax description. %token NAME NUMBER STRING ERE %token FUNC_NAME /* Name followed by '(' without white space. */ /* Keywords */ %token Begin End /* 'BEGIN' 'END' */ %token Break Continue Delete Do Else /* 'break' 'continue' 'delete' 'do' 'else' */ %token Exit For Function If In /* 'exit' 'for' 'function' 'if' 'in' */ %token Next Print Printf Return While /* 'next' 'print' 'printf' 'return' 'while' */ /* Reserved function names */ %token BUILTIN_FUNC_NAME /* One token for the following: * atan2 cos sin exp log sqrt int rand srand * gsub index length match split sprintf sub * substr tolower toupper close system */ %token GETLINE /* Syntactically different from other built-ins. */ /* Two-character tokens. */ %token ADD_ASSIGN SUB_ASSIGN MUL_ASSIGN DIV_ASSIGN MOD_ASSIGN POW_ASSIGN /* '+=' '-=' '*=' '/=' '%=' '^=' */ %token OR AND NO_MATCH EQ LE GE NE INCR DECR APPEND /* '||' '&&' '!~' '==' '<=' '>=' '!=' '++' '--' '>>' */ /* One-character tokens. */ %token '{' '}' '(' ')' '[' ']' ',' ';' NEWLINE %token '+' '-' '*' '%' '^' '!' '>' '<' '|' '?' ':' '~' '$' '=' %start program %% program : item_list | item_list item ; item_list : /* empty */ | item_list item terminator ; item : action | pattern action | normal_pattern | Function NAME '(' param_list_opt ')' newline_opt action | Function FUNC_NAME '(' param_list_opt ')' newline_opt action ; param_list_opt : /* empty */ | param_list ; param_list : NAME | param_list ',' NAME ; pattern : normal_pattern | special_pattern ; normal_pattern : expr | expr ',' newline_opt expr ; special_pattern : Begin | End ; action : '{' newline_opt '}' | '{' newline_opt terminated_statement_list '}' | '{' newline_opt unterminated_statement_list '}' ; terminator : terminator NEWLINE | ';' | NEWLINE ; terminated_statement_list : terminated_statement | terminated_statement_list terminated_statement ; unterminated_statement_list : unterminated_statement | terminated_statement_list unterminated_statement ; terminated_statement : action newline_opt | If '(' expr ')' newline_opt terminated_statement | If '(' expr ')' newline_opt terminated_statement Else newline_opt terminated_statement | While '(' expr ')' newline_opt terminated_statement | For '(' simple_statement_opt ';' expr_opt ';' simple_statement_opt ')' newline_opt terminated_statement | For '(' NAME In NAME ')' newline_opt terminated_statement | ';' newline_opt | terminatable_statement NEWLINE newline_opt | terminatable_statement ';' newline_opt ; unterminated_statement : terminatable_statement | If '(' expr ')' newline_opt unterminated_statement | If '(' expr ')' newline_opt terminated_statement Else newline_opt unterminated_statement | While '(' expr ')' newline_opt unterminated_statement | For '(' simple_statement_opt ';' expr_opt ';' simple_statement_opt ')' newline_opt unterminated_statement | For '(' NAME In NAME ')' newline_opt unterminated_statement ; terminatable_statement : simple_statement | Break | Continue | Next | Exit expr_opt | Return expr_opt | Do newline_opt terminated_statement While '(' expr ')' ; simple_statement_opt : /* empty */ | simple_statement ; simple_statement : Delete NAME '[' expr_list ']' | expr | print_statement ; print_statement : simple_print_statement | simple_print_statement output_redirection ; simple_print_statement : Print print_expr_list_opt | Print '(' multiple_expr_list ')' | Printf print_expr_list | Printf '(' multiple_expr_list ')' ; output_redirection : '>' expr | APPEND expr | '|' expr ; expr_list_opt : /* empty */ | expr_list ; expr_list : expr | multiple_expr_list ; multiple_expr_list : expr ',' newline_opt expr | multiple_expr_list ',' newline_opt expr ; expr_opt : /* empty */ | expr ; expr : unary_expr | non_unary_expr ; unary_expr : '+' expr | '-' expr | unary_expr '^' expr | unary_expr '*' expr | unary_expr '/' expr | unary_expr '%' expr | unary_expr '+' expr | unary_expr '-' expr | unary_expr non_unary_expr | unary_expr '<' expr | unary_expr LE expr | unary_expr NE expr | unary_expr EQ expr | unary_expr '>' expr | unary_expr GE expr | unary_expr '~' expr | unary_expr NO_MATCH expr | unary_expr In NAME | unary_expr AND newline_opt expr | unary_expr OR newline_opt expr | unary_expr '?' expr ':' expr | unary_input_function ; non_unary_expr : '(' expr ')' | '!' expr | non_unary_expr '^' expr | non_unary_expr '*' expr | non_unary_expr '/' expr | non_unary_expr '%' expr | non_unary_expr '+' expr | non_unary_expr '-' expr | non_unary_expr non_unary_expr | non_unary_expr '<' expr | non_unary_expr LE expr | non_unary_expr NE expr | non_unary_expr EQ expr | non_unary_expr '>' expr | non_unary_expr GE expr | non_unary_expr '~' expr | non_unary_expr NO_MATCH expr | non_unary_expr In NAME | '(' multiple_expr_list ')' In NAME | non_unary_expr AND newline_opt expr | non_unary_expr OR newline_opt expr | non_unary_expr '?' expr ':' expr | NUMBER | STRING | lvalue | ERE | lvalue INCR | lvalue DECR | INCR lvalue | DECR lvalue | lvalue POW_ASSIGN expr | lvalue MOD_ASSIGN expr | lvalue MUL_ASSIGN expr | lvalue DIV_ASSIGN expr | lvalue ADD_ASSIGN expr | lvalue SUB_ASSIGN expr | lvalue '=' expr | FUNC_NAME '(' expr_list_opt ')' /* no white space allowed before '(' */ | BUILTIN_FUNC_NAME '(' expr_list_opt ')' | BUILTIN_FUNC_NAME | non_unary_input_function ; print_expr_list_opt : /* empty */ | print_expr_list ; print_expr_list : print_expr | print_expr_list ',' newline_opt print_expr ; print_expr : unary_print_expr | non_unary_print_expr ; unary_print_expr : '+' print_expr | '-' print_expr | unary_print_expr '^' print_expr | unary_print_expr '*' print_expr | unary_print_expr '/' print_expr | unary_print_expr '%' print_expr | unary_print_expr '+' print_expr | unary_print_expr '-' print_expr | unary_print_expr non_unary_print_expr | unary_print_expr '~' print_expr | unary_print_expr NO_MATCH print_expr | unary_print_expr In NAME | unary_print_expr AND newline_opt print_expr | unary_print_expr OR newline_opt print_expr | unary_print_expr '?' print_expr ':' print_expr ; non_unary_print_expr : '(' expr ')' | '!' print_expr | non_unary_print_expr '^' print_expr | non_unary_print_expr '*' print_expr | non_unary_print_expr '/' print_expr | non_unary_print_expr '%' print_expr | non_unary_print_expr '+' print_expr | non_unary_print_expr '-' print_expr | non_unary_print_expr non_unary_print_expr | non_unary_print_expr '~' print_expr | non_unary_print_expr NO_MATCH print_expr | non_unary_print_expr In NAME | '(' multiple_expr_list ')' In NAME | non_unary_print_expr AND newline_opt print_expr | non_unary_print_expr OR newline_opt print_expr | non_unary_print_expr '?' print_expr ':' print_expr | NUMBER | STRING | lvalue | ERE | lvalue INCR | lvalue DECR | INCR lvalue | DECR lvalue | lvalue POW_ASSIGN print_expr | lvalue MOD_ASSIGN print_expr | lvalue MUL_ASSIGN print_expr | lvalue DIV_ASSIGN print_expr | lvalue ADD_ASSIGN print_expr | lvalue SUB_ASSIGN print_expr | lvalue '=' print_expr | FUNC_NAME '(' expr_list_opt ')' /* no white space allowed before '(' */ | BUILTIN_FUNC_NAME '(' expr_list_opt ')' | BUILTIN_FUNC_NAME ; lvalue : NAME | NAME '[' expr_list ']' | '$' expr ; non_unary_input_function : simple_get | simple_get '<' expr | non_unary_expr '|' simple_get ; unary_input_function : unary_expr '|' simple_get ; simple_get : GETLINE | GETLINE lvalue ; newline_opt : /* empty */ | newline_opt NEWLINE ; This grammar has several ambiguities that shall be resolved as follows: * Operator precedence and associativity shall be as described in Table 4-1, Expressions in Decreasing Precedence in awk. * In case of ambiguity, an else shall be associated with the most immediately preceding if that would satisfy the grammar. * In some contexts, a <slash> ('/') that is used to surround an ERE could also be the division operator. This shall be resolved in such a way that wherever the division operator could appear, a <slash> is assumed to be the division operator. (There is no unary division operator.) Each expression in an awk program shall conform to the precedence and associativity rules, even when this is not needed to resolve an ambiguity. For example, because '$' has higher precedence than '++', the string "$x++--" is not a valid awk expression, even though it is unambiguously parsed by the grammar as "$(x++)--". One convention that might not be obvious from the formal grammar is where <newline> characters are acceptable. There are several obvious placements such as terminating a statement, and a <backslash> can be used to escape <newline> characters between any lexical tokens. In addition, <newline> characters without <backslash> characters can follow a comma, an open brace, logical AND operator ("&&"), logical OR operator ("||"), the do keyword, the else keyword, and the closing parenthesis of an if, for, or while statement. For example: { print $1, $2 } Lexical Conventions The lexical conventions for awk programs, with respect to the preceding grammar, shall be as follows: 1. Except as noted, awk shall recognize the longest possible token or delimiter beginning at a given point. 2. A comment shall consist of any characters beginning with the <number-sign> character and terminated by, but excluding the next occurrence of, a <newline>. Comments shall have no effect, except to delimit lexical tokens. 3. The <newline> shall be recognized as the token NEWLINE. 4. A <backslash> character immediately followed by a <newline> shall have no effect. 5. The token STRING shall represent a string constant. A string constant shall begin with the character '"'. Within a string constant, a <backslash> character shall be considered to begin an escape sequence as specified in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v'). In addition, the escape sequences in Table 4-2, Escape Sequences in awk shall be recognized. A <newline> shall not occur within a string constant. A string constant shall be terminated by the first unescaped occurrence of the character '"' after the one that begins the string constant. The value of the string shall be the sequence of all unescaped characters and values of escape sequences between, but not including, the two delimiting '"' characters. 6. The token ERE represents an extended regular expression constant. An ERE constant shall begin with the <slash> character. Within an ERE constant, a <backslash> character shall be considered to begin an escape sequence as specified in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation. In addition, the escape sequences in Table 4-2, Escape Sequences in awk shall be recognized. The application shall ensure that a <newline> does not occur within an ERE constant. An ERE constant shall be terminated by the first unescaped occurrence of the <slash> character after the one that begins the ERE constant. The extended regular expression represented by the ERE constant shall be the sequence of all unescaped characters and values of escape sequences between, but not including, the two delimiting <slash> characters. 7. A <blank> shall have no effect, except to delimit lexical tokens or within STRING or ERE tokens. 8. The token NUMBER shall represent a numeric constant. Its form and numeric value shall either be equivalent to the decimal- floating-constant token as specified by the ISO C standard, or it shall be a sequence of decimal digits and shall be evaluated as an integer constant in decimal. In addition, implementations may accept numeric constants with the form and numeric value equivalent to the hexadecimal-constant and hexadecimal-floating-constant tokens as specified by the ISO C standard. If the value is too large or too small to be representable (see Section 1.1.2, Concepts Derived from the ISO C Standard), the behavior is undefined. 9. A sequence of underscores, digits, and alphabetics from the portable character set (see the Base Definitions volume of POSIX.12017, Section 6.1, Portable Character Set), beginning with an <underscore> or alphabetic character, shall be considered a word. 10. The following words are keywords that shall be recognized as individual tokens; the name of the token is the same as the keyword: BEGIN delete END function in printf break do exit getline next return continue else for if print while 11. The following words are names of built-in functions and shall be recognized as the token BUILTIN_FUNC_NAME: atan2 gsub log split sub toupper close index match sprintf substr cos int rand sqrt system exp length sin srand tolower The above-listed keywords and names of built-in functions are considered reserved words. 12. The token NAME shall consist of a word that is not a keyword or a name of a built-in function and is not followed immediately (without any delimiters) by the '(' character. 13. The token FUNC_NAME shall consist of a word that is not a keyword or a name of a built-in function, followed immediately (without any delimiters) by the '(' character. The '(' character shall not be included as part of the token. 14. The following two-character sequences shall be recognized as the named tokens: Token Name Sequence Token Name Sequence ADD_ASSIGN += NO_MATCH !~ SUB_ASSIGN -= EQ == MUL_ASSIGN *= LE <= DIV_ASSIGN /= GE >= MOD_ASSIGN %= NE != POW_ASSIGN ^= INCR ++ OR || DECR -- AND && APPEND >> 15. The following single characters shall be recognized as tokens whose names are the character: <newline> { } ( ) [ ] , ; + - * % ^ ! > < | ? : ~ $ = There is a lexical ambiguity between the token ERE and the tokens '/' and DIV_ASSIGN. When an input sequence begins with a <slash> character in any syntactic context where the token '/' or DIV_ASSIGN could appear as the next token in a valid program, the longer of those two tokens that can be recognized shall be recognized. In any other syntactic context where the token ERE could appear as the next token in a valid program, the token ERE shall be recognized. EXIT STATUS top The following exit values shall be returned: 0 All input files were processed successfully. >0 An error occurred. The exit status can be altered within the program by using an exit expression. CONSEQUENCES OF ERRORS top If any file operand is specified and the named file cannot be accessed, awk shall write a diagnostic message to standard error and terminate without any further action. If the program specified by either the program operand or a progfile operand is not a valid awk program (as specified in the EXTENDED DESCRIPTION section), the behavior is undefined. The following sections are informative. APPLICATION USAGE top The index, length, match, and substr functions should not be confused with similar functions in the ISO C standard; the awk versions deal with characters, while the ISO C standard deals with bytes. Because the concatenation operation is represented by adjacent expressions rather than an explicit operator, it is often necessary to use parentheses to enforce the proper evaluation precedence. When using awk to process pathnames, it is recommended that LC_ALL, or at least LC_CTYPE and LC_COLLATE, are set to POSIX or C in the environment, since pathnames can contain byte sequences that do not form valid characters in some locales, in which case the utility's behavior would be undefined. In the POSIX locale each byte is a valid single-byte character, and therefore this problem is avoided. On implementations where the "==" operator checks if strings collate equally, applications needing to check whether strings are identical can use: length(a) == length(b) && index(a,b) == 1 On implementations where the "==" operator checks if strings are identical, applications needing to check whether strings collate equally can use: a <= b && a >= b EXAMPLES top The awk program specified in the command line is most easily specified within single-quotes (for example, 'program') for applications using sh, because awk programs commonly contain characters that are special to the shell, including double- quotes. In the cases where an awk program contains single-quote characters, it is usually easiest to specify most of the program as strings within single-quotes concatenated by the shell with quoted single-quote characters. For example: awk '/'\''/ { print "quote:", $0 }' prints all lines from the standard input containing a single- quote character, prefixed with quote:. The following are examples of simple awk programs: 1. Write to the standard output all input lines for which field 3 is greater than 5: $3 > 5 2. Write every tenth line: (NR % 10) == 0 3. Write any line with a substring matching the regular expression: /(G|D)(2[0-9][[:alpha:]]*)/ 4. Print any line with a substring containing a 'G' or 'D', followed by a sequence of digits and characters. This example uses character classes digit and alpha to match language- independent digit and alphabetic characters respectively: /(G|D)([[:digit:][:alpha:]]*)/ 5. Write any line in which the second field matches the regular expression and the fourth field does not: $2 ~ /xyz/ && $4 !~ /xyz/ 6. Write any line in which the second field contains a <backslash>: $2 ~ /\\/ 7. Write any line in which the second field contains a <backslash>. Note that <backslash>-escapes are interpreted twice; once in lexical processing of the string and once in processing the regular expression: $2 ~ "\\\\" 8. Write the second to the last and the last field in each line. Separate the fields by a <colon>: {OFS=":";print $(NF-1), $NF} 9. Write the line number and number of fields in each line. The three strings representing the line number, the <colon>, and the number of fields are concatenated and that string is written to standard output: {print NR ":" NF} 10. Write lines longer than 72 characters: length($0) > 72 11. Write the first two fields in opposite order separated by OFS: { print $2, $1 } 12. Same, with input fields separated by a <comma> or <space> and <tab> characters, or both: BEGIN { FS = ",[ \t]*|[ \t]+" } { print $2, $1 } 13. Add up the first column, print sum, and average: {s += $1 } END {print "sum is ", s, " average is", s/NR} 14. Write fields in reverse order, one per line (many lines out for each line in): { for (i = NF; i > 0; --i) print $i } 15. Write all lines between occurrences of the strings start and stop: /start/, /stop/ 16. Write all lines whose first field is different from the previous one: $1 != prev { print; prev = $1 } 17. Simulate echo: BEGIN { for (i = 1; i < ARGC; ++i) printf("%s%s", ARGV[i], i==ARGC-1?"\n":" ") } 18. Write the path prefixes contained in the PATH environment variable, one per line: BEGIN { n = split (ENVIRON["PATH"], path, ":") for (i = 1; i <= n; ++i) print path[i] } 19. If there is a file named input containing page headers of the form: Page # and a file named program that contains: /Page/ { $2 = n++; } { print } then the command line: awk -f program n=5 input prints the file input, filling in page numbers starting at 5. RATIONALE top This description is based on the new awk, ``nawk'', (see the referenced The AWK Programming Language), which introduced a number of new features to the historical awk: 1. New keywords: delete, do, function, return 2. New built-in functions: atan2, close, cos, gsub, match, rand, sin, srand, sub, system 3. New predefined variables: FNR, ARGC, ARGV, RSTART, RLENGTH, SUBSEP 4. New expression operators: ?, :, ,, ^ 5. The FS variable and the third argument to split, now treated as extended regular expressions. 6. The operator precedence, changed to more closely match the C language. Two examples of code that operate differently are: while ( n /= 10 > 1) ... if (!"wk" ~ /bwk/) ... Several features have been added based on newer implementations of awk: * Multiple instances of -f progfile are permitted. * The new option -v assignment. * The new predefined variable ENVIRON. * New built-in functions toupper and tolower. * More formatting capabilities are added to printf to match the ISO C standard. Earlier versions of this standard required implementations to support multiple adjacent <semicolon>s, lines with one or more <semicolon> before a rule (pattern-action pairs), and lines with only <semicolon>(s). These are not required by this standard and are considered poor programming practice, but can be accepted by an implementation of awk as an extension. The overall awk syntax has always been based on the C language, with a few features from the shell command language and other sources. Because of this, it is not completely compatible with any other language, which has caused confusion for some users. It is not the intent of the standard developers to address such issues. A few relatively minor changes toward making the language more compatible with the ISO C standard were made; most of these changes are based on similar changes in recent implementations, as described above. There remain several C-language conventions that are not in awk. One of the notable ones is the <comma> operator, which is commonly used to specify multiple expressions in the C language for statement. Also, there are various places where awk is more restrictive than the C language regarding the type of expression that can be used in a given context. These limitations are due to the different features that the awk language does provide. Regular expressions in awk have been extended somewhat from historical implementations to make them a pure superset of extended regular expressions, as defined by POSIX.12008 (see the Base Definitions volume of POSIX.12017, Section 9.4, Extended Regular Expressions). The main extensions are internationalization features and interval expressions. Historical implementations of awk have long supported <backslash>-escape sequences as an extension to extended regular expressions, and this extension has been retained despite inconsistency with other utilities. The number of escape sequences recognized in both extended regular expressions and strings has varied (generally increasing with time) among implementations. The set specified by POSIX.12008 includes most sequences known to be supported by popular implementations and by the ISO C standard. One sequence that is not supported is hexadecimal value escapes beginning with '\x'. This would allow values expressed in more than 9 bits to be used within awk as in the ISO C standard. However, because this syntax has a non- deterministic length, it does not permit the subsequent character to be a hexadecimal digit. This limitation can be dealt with in the C language by the use of lexical string concatenation. In the awk language, concatenation could also be a solution for strings, but not for extended regular expressions (either lexical ERE tokens or strings used dynamically as regular expressions). Because of this limitation, the feature has not been added to POSIX.12008. When a string variable is used in a context where an extended regular expression normally appears (where the lexical token ERE is used in the grammar) the string does not contain the literal <slash> characters. Some versions of awk allow the form: func name(args, ... ) { statements } This has been deprecated by the authors of the language, who asked that it not be specified. Historical implementations of awk produce an error if a next statement is executed in a BEGIN action, and cause awk to terminate if a next statement is executed in an END action. This behavior has not been documented, and it was not believed that it was necessary to standardize it. The specification of conversions between string and numeric values is much more detailed than in the documentation of historical implementations or in the referenced The AWK Programming Language. Although most of the behavior is designed to be intuitive, the details are necessary to ensure compatible behavior from different implementations. This is especially important in relational expressions since the types of the operands determine whether a string or numeric comparison is performed. From the perspective of an application developer, it is usually sufficient to expect intuitive behavior and to force conversions (by adding zero or concatenating a null string) when the type of an expression does not obviously match what is needed. The intent has been to specify historical practice in almost all cases. The one exception is that, in historical implementations, variables and constants maintain both string and numeric values after their original value is converted by any use. This means that referencing a variable or constant can have unexpected side-effects. For example, with historical implementations the following program: { a = "+2" b = 2 if (NR % 2) c = a + b if (a == b) print "numeric comparison" else print "string comparison" } would perform a numeric comparison (and output numeric comparison) for each odd-numbered line, but perform a string comparison (and output string comparison) for each even-numbered line. POSIX.12008 ensures that comparisons will be numeric if necessary. With historical implementations, the following program: BEGIN { OFMT = "%e" print 3.14 OFMT = "%f" print 3.14 } would output "3.140000e+00" twice, because in the second print statement the constant "3.14" would have a string value from the previous conversion. POSIX.12008 requires that the output of the second print statement be "3.140000". The behavior of historical implementations was seen as too unintuitive and unpredictable. It was pointed out that with the rules contained in early drafts, the following script would print nothing: BEGIN { y[1.5] = 1 OFMT = "%e" print y[1.5] } Therefore, a new variable, CONVFMT, was introduced. The OFMT variable is now restricted to affecting output conversions of numbers to strings and CONVFMT is used for internal conversions, such as comparisons or array indexing. The default value is the same as that for OFMT, so unless a program changes CONVFMT (which no historical program would do), it will receive the historical behavior associated with internal string conversions. The POSIX awk lexical and syntactic conventions are specified more formally than in other sources. Again the intent has been to specify historical practice. One convention that may not be obvious from the formal grammar as in other verbal descriptions is where <newline> characters are acceptable. There are several obvious placements such as terminating a statement, and a <backslash> can be used to escape <newline> characters between any lexical tokens. In addition, <newline> characters without <backslash> characters can follow a comma, an open brace, a logical AND operator ("&&"), a logical OR operator ("||"), the do keyword, the else keyword, and the closing parenthesis of an if, for, or while statement. For example: { print $1, $2 } The requirement that awk add a trailing <newline> to the program argument text is to simplify the grammar, making it match a text file in form. There is no way for an application or test suite to determine whether a literal <newline> is added or whether awk simply acts as if it did. POSIX.12008 requires several changes from historical implementations in order to support internationalization. Probably the most subtle of these is the use of the decimal-point character, defined by the LC_NUMERIC category of the locale, in representations of floating-point numbers. This locale-specific character is used in recognizing numeric input, in converting between strings and numeric values, and in formatting output. However, regardless of locale, the <period> character (the decimal-point character of the POSIX locale) is the decimal-point character recognized in processing awk programs (including assignments in command line arguments). This is essentially the same convention as the one used in the ISO C standard. The difference is that the C language includes the setlocale() function, which permits an application to modify its locale. Because of this capability, a C application begins executing with its locale set to the C locale, and only executes in the environment-specified locale after an explicit call to setlocale(). However, adding such an elaborate new feature to the awk language was seen as inappropriate for POSIX.12008. It is possible to execute an awk program explicitly in any desired locale by setting the environment in the shell. The undefined behavior resulting from NULs in extended regular expressions allows future extensions for the GNU gawk program to process binary data. The behavior in the case of invalid awk programs (including lexical, syntactic, and semantic errors) is undefined because it was considered overly limiting on implementations to specify. In most cases such errors can be expected to produce a diagnostic and a non-zero exit status. However, some implementations may choose to extend the language in ways that make use of certain invalid constructs. Other invalid constructs might be deemed worthy of a warning, but otherwise cause some reasonable behavior. Still other constructs may be very difficult to detect in some implementations. Also, different implementations might detect a given error during an initial parsing of the program (before reading any input files) while others might detect it when executing the program after reading some input. Implementors should be aware that diagnosing errors as early as possible and producing useful diagnostics can ease debugging of applications, and thus make an implementation more usable. The unspecified behavior from using multi-character RS values is to allow possible future extensions based on extended regular expressions used for record separators. Historical implementations take the first character of the string and ignore the others. Unspecified behavior when split(string,array,<null>) is used is to allow a proposed future extension that would split up a string into an array of individual characters. In the context of the getline function, equally good arguments for different precedences of the | and < operators can be made. Historical practice has been that: getline < "a" "b" is parsed as: ( getline < "a" ) "b" although many would argue that the intent was that the file ab should be read. However: getline < "x" + 1 parses as: getline < ( "x" + 1 ) Similar problems occur with the | version of getline, particularly in combination with $. For example: $"echo hi" | getline (This situation is particularly problematic when used in a print statement, where the |getline part might be a redirection of the print.) Since in most cases such constructs are not (or at least should not) be used (because they have a natural ambiguity for which there is no conventional parsing), the meaning of these constructs has been made explicitly unspecified. (The effect is that a conforming application that runs into the problem must parenthesize to resolve the ambiguity.) There appeared to be few if any actual uses of such constructs. Grammars can be written that would cause an error under these circumstances. Where backwards-compatibility is not a large consideration, implementors may wish to use such grammars. Some historical implementations have allowed some built-in functions to be called without an argument list, the result being a default argument list chosen in some ``reasonable'' way. Use of length as a synonym for length($0) is the only one of these forms that is thought to be widely known or widely used; this particular form is documented in various places (for example, most historical awk reference pages, although not in the referenced The AWK Programming Language) as legitimate practice. With this exception, default argument lists have always been undocumented and vaguely defined, and it is not at all clear how (or if) they should be generalized to user-defined functions. They add no useful functionality and preclude possible future extensions that might need to name functions without calling them. Not standardizing them seems the simplest course. The standard developers considered that length merited special treatment, however, since it has been documented in the past and sees possibly substantial use in historical programs. Accordingly, this usage has been made legitimate, but Issue 5 removed the obsolescent marking for XSI-conforming implementations and many otherwise conforming applications depend on this feature. In sub and gsub, if repl is a string literal (the lexical token STRING), then two consecutive <backslash> characters should be used in the string to ensure a single <backslash> will precede the <ampersand> when the resultant string is passed to the function. (For example, to specify one literal <ampersand> in the replacement string, use gsub(ERE, "\\&").) Historically, the only special character in the repl argument of sub and gsub string functions was the <ampersand> ('&') character and preceding it with the <backslash> character was used to turn off its special meaning. The description in the ISO POSIX2:1993 standard introduced behavior such that the <backslash> character was another special character and it was unspecified whether there were any other special characters. This description introduced several portability problems, some of which are described below, and so it has been replaced with the more historical description. Some of the problems include: * Historically, to create the replacement string, a script could use gsub(ERE, "\\&"), but with the ISO POSIX2:1993 standard wording, it was necessary to use gsub(ERE, "\\\\&"). The <backslash> characters are doubled here because all string literals are subject to lexical analysis, which would reduce each pair of <backslash> characters to a single <backslash> before being passed to gsub. * Since it was unspecified what the special characters were, for portable scripts to guarantee that characters are printed literally, each character had to be preceded with a <backslash>. (For example, a portable script had to use gsub(ERE, "\\h\\i") to produce a replacement string of "hi".) The description for comparisons in the ISO POSIX2:1993 standard did not properly describe historical practice because of the way numeric strings are compared as numbers. The current rules cause the following code: if (0 == "000") print "strange, but true" else print "not true" to do a numeric comparison, causing the if to succeed. It should be intuitively obvious that this is incorrect behavior, and indeed, no historical implementation of awk actually behaves this way. To fix this problem, the definition of numeric string was enhanced to include only those values obtained from specific circumstances (mostly external sources) where it is not possible to determine unambiguously whether the value is intended to be a string or a numeric. Variables that are assigned to a numeric string shall also be treated as a numeric string. (For example, the notion of a numeric string can be propagated across assignments.) In comparisons, all variables having the uninitialized value are to be treated as a numeric operand evaluating to the numeric value zero. Uninitialized variables include all types of variables including scalars, array elements, and fields. The definition of an uninitialized value in Variables and Special Variables is necessary to describe the value placed on uninitialized variables and on fields that are valid (for example, < $NF) but have no characters in them and to describe how these variables are to be used in comparisons. A valid field, such as $1, that has no characters in it can be obtained from an input line of "\t\t" when FS='\t'. Historically, the comparison ($1<10) was done numerically after evaluating $1 to the value zero. The phrase ``... also shall have the numeric value of the numeric string'' was removed from several sections of the ISO POSIX2:1993 standard because is specifies an unnecessary implementation detail. It is not necessary for POSIX.12008 to specify that these objects be assigned two different values. It is only necessary to specify that these objects may evaluate to two different values depending on context. Historical implementations of awk did not parse hexadecimal integer or floating constants like "0xa" and "0xap0". Due to an oversight, the 2001 through 2004 editions of this standard required support for hexadecimal floating constants. This was due to the reference to atof(). This version of the standard allows but does not require implementations to use atof() and includes a description of how floating-point numbers are recognized as an alternative to match historic behavior. The intent of this change is to allow implementations to recognize floating-point constants according to either the ISO/IEC 9899:1990 standard or ISO/IEC 9899:1999 standard, and to allow (but not require) implementations to recognize hexadecimal integer constants. Historical implementations of awk did not support floating-point infinities and NaNs in numeric strings; e.g., "-INF" and "NaN". However, implementations that use the atof() or strtod() functions to do the conversion picked up support for these values if they used a ISO/IEC 9899:1999 standard version of the function instead of a ISO/IEC 9899:1990 standard version. Due to an oversight, the 2001 through 2004 editions of this standard did not allow support for infinities and NaNs, but in this revision support is allowed (but not required). This is a silent change to the behavior of awk programs; for example, in the POSIX locale the expression: ("-INF" + 0 < 0) formerly had the value 0 because "-INF" converted to 0, but now it may have the value 0 or 1. FUTURE DIRECTIONS top A future version of this standard may require the "!=" and "==" operators to perform string comparisons by checking if the strings are identical (and not by checking if they collate equally). SEE ALSO top Section 1.3, Grammar Conventions, grep(1p), lex(1p), sed(1p) The Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation, Section 6.1, Portable Character Set, Chapter 8, Environment Variables, Chapter 9, Regular Expressions, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, atof(3p), exec(1p), isspace(3p), popen(3p), setlocale(3p), strtod(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 AWK(1P) Pages that refer to this page: bc(1p), colrm(1), join(1p), printf(1p), sed(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. kill(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training Other versions of this page are provided by these projects: coreutils procps-ng kill(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | ARGUMENTS | OPTIONS | EXIT STATUS | NOTES | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY KILL(1) User Commands KILL(1) NAME top kill - terminate a process SYNOPSIS top kill [-signal|-s signal|-p] [-q value] [-a] [--timeout milliseconds signal] [--] pid|name... kill -l [number] | -L DESCRIPTION top The command kill sends the specified signal to the specified processes or process groups. If no signal is specified, the TERM signal is sent. The default action for this signal is to terminate the process. This signal should be used in preference to the KILL signal (number 9), since a process may install a handler for the TERM signal in order to perform clean-up steps before terminating in an orderly fashion. If a process does not terminate after a TERM signal has been sent, then the KILL signal may be used; be aware that the latter signal cannot be caught, and so does not give the target process the opportunity to perform any clean-up before terminating. Most modern shells have a builtin kill command, with a usage rather similar to that of the command described here. The --all, --pid, and --queue options, and the possibility to specify processes by command name, are local extensions. If signal is 0, then no actual signal is sent, but error checking is still performed. ARGUMENTS top The list of processes to be signaled can be a mixture of names and PIDs. pid Each pid can be expressed in one of the following ways: n where n is larger than 0. The process with PID n is signaled. 0 All processes in the current process group are signaled. -1 All processes with a PID larger than 1 are signaled. -n where n is larger than 1. All processes in process group n are signaled. When an argument of the form '-n' is given, and it is meant to denote a process group, either a signal must be specified first, or the argument must be preceded by a '--' option, otherwise it will be taken as the signal to send. name All processes invoked using this name will be signaled. OPTIONS top -s, --signal signal The signal to send. It may be given as a name or a number. -l, --list [number] Print a list of signal names, or convert the given signal number to a name. The signals can be found in /usr/include/linux/signal.h. -L, --table Similar to -l, but it will print signal names and their corresponding numbers. -a, --all Do not restrict the command-name-to-PID conversion to processes with the same UID as the present process. -p, --pid Only print the process ID (PID) of the named processes, do not send any signals. -r, --require-handler Do not send the signal if it is not caught in userspace by the signalled process. --verbose Print PID(s) that will be signaled with kill along with the signal. -q, --queue value Send the signal using sigqueue(3) rather than kill(2). The value argument is an integer that is sent along with the signal. If the receiving process has installed a handler for this signal using the SA_SIGINFO flag to sigaction(2), then it can obtain this data via the si_sigval field of the siginfo_t structure. --timeout milliseconds signal Send a signal defined in the usual way to a process, followed by an additional signal after a specified delay. The --timeout option causes kill to wait for a period defined in milliseconds before sending a follow-up signal to the process. This feature is implemented using the Linux kernel PID file descriptor feature in order to guarantee that the follow-up signal is sent to the same process or not sent if the process no longer exists. Note that the operating system may re-use PIDs and implementing an equivalent feature in a shell using kill and sleep would be subject to races whereby the follow-up signal might be sent to a different process that used a recycled PID. The --timeout option can be specified multiple times: the signals are sent sequentially with the specified timeouts. The --timeout option can be combined with the --queue option. As an example, the following command sends the signals QUIT, TERM and KILL in sequence and waits for 1000 milliseconds between sending the signals: kill --verbose --timeout 1000 TERM --timeout 1000 KILL \ --signal QUIT 12345 EXIT STATUS top kill has the following exit status values: 0 success 1 failure 64 partial success (when more than one process specified) NOTES top Although it is possible to specify the TID (thread ID, see gettid(2)) of one of the threads in a multithreaded process as the argument of kill, the signal is nevertheless directed to the process (i.e., the entire thread group). In other words, it is not possible to send a signal to an explicitly selected thread in a multithreaded process. The signal will be delivered to an arbitrarily selected thread in the target process that is not blocking the signal. For more details, see signal(7) and the description of CLONE_THREAD in clone(2). Various shells provide a builtin kill command that is preferred in relation to the kill(1) executable described by this manual. The easiest way to ensure one is executing the command described in this page is to use the full path when calling the command, for example: /bin/kill --version AUTHORS top Salvatore Valente <svalente@mit.edu>, Karel Zak <kzak@redhat.com> The original version was taken from BSD 4.4. SEE ALSO top bash(1), tcsh(1), sigaction(2), kill(2), sigqueue(3), signal(7) REPORTING BUGS top For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY top The kill command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at https://www.kernel.org/pub/linux/utils/util-linux/. If you have a bug report for this manual page, send it to util-linux@vger.kernel.org. This page was obtained from the project's upstream Git repository git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org util-linux 2.39.594-1e0ad 2023-07-19 KILL(1) Pages that refer to this page: fuser(1), kill(1), killall(1), pgrep(1), pmsignal(1), skill(1), tcpdump(1), timeout(1), xargs(1), kill(2), sigaction(2), signal(2), posix_spawn(3), signal(7), ldattach(8), lsof(8), systemd-coredump(8), tcpdump(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Clean up all zombie processes by sending SIGTERM signal to their parent process, which requests them to terminate. Bash Command:<START>kill $(ps -A -ostat,ppid | awk '/[zZ]/{print $2}')<END>

Clears terminal screen.

echo `clear`

['echo', 'clear']

Output a Bash command to accomplish the following task. Task: Clears terminal screen. Bash Command:<START>echo `clear`<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # echo\n\n> Print given arguments.\n> More information: <https://www.gnu.org/software/coreutils/echo>.\n\n- Print a text message. Note: quotes are optional:\n\n`echo "{{Hello World}}"`\n\n- Print a message with environment variables:\n\n`echo "{{My path is $PATH}}"`\n\n- Print a message without the trailing newline:\n\n`echo -n "{{Hello World}}"`\n\n- Append a message to the file:\n\n`echo "{{Hello World}}" >> {{file.txt}}`\n\n- Enable interpretation of backslash escapes (special characters):\n\n`echo -e "{{Column 1\tColumn 2}}"`\n\n- Print the exit status of the last executed command (Note: In Windows Command Prompt and PowerShell the equivalent commands are `echo %errorlevel%` and `$lastexitcode` respectively):\n\n`echo $?`\n # clear\n\n> Clears the screen of the terminal.\n> More information: <https://manned.org/clear>.\n\n- Clear the screen (equivalent to pressing Control-L in Bash shell):\n\n`clear`\n\n- Clear the screen but keep the terminal's scrollback buffer:\n\n`clear -x`\n\n- Indicate the type of terminal to clean (defaults to the value of the environment variable `TERM`):\n\n`clear -T {{type_of_terminal}}`\n\n- Display the version of `ncurses` used by `clear`:\n\n`clear -V`\n Task: Clears terminal screen. Bash Command:<START>echo `clear`<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: echo(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training echo(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON ECHO(1) User Commands ECHO(1) NAME top echo - display a line of text SYNOPSIS top echo [SHORT-OPTION]... [STRING]... echo LONG-OPTION DESCRIPTION top Echo the STRING(s) to standard output. -n do not output the trailing newline -e enable interpretation of backslash escapes -E disable interpretation of backslash escapes (default) --help display this help and exit --version output version information and exit If -e is in effect, the following sequences are recognized: \\ backslash \a alert (BEL) \b backspace \c produce no further output \e escape \f form feed \n new line \r carriage return \t horizontal tab \v vertical tab \0NNN byte with octal value NNN (1 to 3 digits) \xHH byte with hexadecimal value HH (1 to 2 digits) NOTE: your shell may have its own version of echo, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports. NOTE: printf(1) is a preferred alternative, which does not have issues outputting option-like strings. AUTHOR top Written by Brian Fox and Chet Ramey. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top printf(1) Full documentation <https://www.gnu.org/software/coreutils/echo> or available locally via: info '(coreutils) echo invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 ECHO(1) Pages that refer to this page: ldapcompare(1), systemd-ask-password(1), systemd-run(1), cpuset(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. clear(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training clear(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | HISTORY | PORTABILITY | SEE ALSO | COLOPHON @CLEAR@(1) General Commands Manual @CLEAR@(1) NAME top @CLEAR@ - clear the terminal screen SYNOPSIS top @CLEAR@ [-Ttype] [-V] [-x] DESCRIPTION top @CLEAR@ clears your terminal's screen if this is possible, including the terminal's scrollback buffer (if the extended E3 capability is defined). @CLEAR@ looks in the environment for the terminal type given by the environment variable TERM, and then in the terminfo database to determine how to clear the screen. @CLEAR@ writes to the standard output. You can redirect the standard output to a file (which prevents @CLEAR@ from actually clearing the screen), and later cat the file to the screen, clearing it at that point. OPTIONS top -T type indicates the type of terminal. Normally this option is unnecessary, because the default is taken from the environment variable TERM. If -T is specified, then the shell variables LINES and COLUMNS will also be ignored. -V reports the version of ncurses which was used in this program, and exits. The options are as follows: -x do not attempt to clear the terminal's scrollback buffer using the extended E3 capability. HISTORY top A clear command appeared in 2.79BSD dated February 24, 1979. Later that was provided in Unix 8th edition (1985). AT&T adapted a different BSD program (tset) to make a new command (tput), and used this to replace the clear command with a shell script which calls tput clear, e.g., /usr/bin/tput ${1:+-T$1} clear 2> /dev/null exit In 1989, when Keith Bostic revised the BSD tput command to make it similar to the AT&T tput, he added a shell script for the clear command: exec tput clear The remainder of the script in each case is a copyright notice. The ncurses clear command began in 1995 by adapting the original BSD clear command (with terminfo, of course). The E3 extension came later: In June 1999, xterm provided an extension to the standard control sequence for clearing the screen. Rather than clearing just the visible part of the screen using printf '\033[2J' one could clear the scrollback using printf '\033[3J' This is documented in XTerm Control Sequences as a feature originating with xterm. A few other terminal developers adopted the feature, e.g., PuTTY in 2006. In April 2011, a Red Hat developer submitted a patch to the Linux kernel, modifying its console driver to do the same thing. The Linux change, part of the 3.0 release, did not mention xterm, although it was cited in the Red Hat bug report (#683733) which led to the change. Again, a few other terminal developers adopted the feature. But the next relevant step was a change to the clear program in 2013 to incorporate this extension. In 2013, the E3 extension was overlooked in @TPUT@ with the clear parameter. That was addressed in 2016 by reorganizing @TPUT@ to share its logic with @CLEAR@ and @TSET@. PORTABILITY top Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7 (POSIX.1-2008) nor X/Open Curses Issue 7 documents @TSET@ or @RESET@. The latter documents tput, which could be used to replace this utility either via a shell script or by an alias (such as a symbolic link) to run @TPUT@ as @CLEAR@. SEE ALSO top @TPUT@(1), terminfo(5), xterm(1). This describes ncurses version @NCURSES_MAJOR@.@NCURSES_MINOR@ (patch @NCURSES_PATCH@). COLOPHON top This page is part of the ncurses (new curses) project. Information about the project can be found at https://www.gnu.org/software/ncurses/ncurses.html. If you have a bug report for this manual page, send it to bug-ncurses-request@gnu.org. This page was obtained from the project's upstream Git mirror of the CVS repository https://github.com/mirror/ncurses.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-03-12.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org @CLEAR@(1) Pages that refer to this page: setterm(1), user_caps(5) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Clears terminal screen. Bash Command:<START>echo `clear`<END>

Clears the terminal screen.

clear

['clear']

Output a Bash command to accomplish the following task. Task: Clears the terminal screen. Bash Command:<START>clear<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # clear\n\n> Clears the screen of the terminal.\n> More information: <https://manned.org/clear>.\n\n- Clear the screen (equivalent to pressing Control-L in Bash shell):\n\n`clear`\n\n- Clear the screen but keep the terminal's scrollback buffer:\n\n`clear -x`\n\n- Indicate the type of terminal to clean (defaults to the value of the environment variable `TERM`):\n\n`clear -T {{type_of_terminal}}`\n\n- Display the version of `ncurses` used by `clear`:\n\n`clear -V`\n Task: Clears the terminal screen. Bash Command:<START>clear<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: clear(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training clear(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | HISTORY | PORTABILITY | SEE ALSO | COLOPHON @CLEAR@(1) General Commands Manual @CLEAR@(1) NAME top @CLEAR@ - clear the terminal screen SYNOPSIS top @CLEAR@ [-Ttype] [-V] [-x] DESCRIPTION top @CLEAR@ clears your terminal's screen if this is possible, including the terminal's scrollback buffer (if the extended E3 capability is defined). @CLEAR@ looks in the environment for the terminal type given by the environment variable TERM, and then in the terminfo database to determine how to clear the screen. @CLEAR@ writes to the standard output. You can redirect the standard output to a file (which prevents @CLEAR@ from actually clearing the screen), and later cat the file to the screen, clearing it at that point. OPTIONS top -T type indicates the type of terminal. Normally this option is unnecessary, because the default is taken from the environment variable TERM. If -T is specified, then the shell variables LINES and COLUMNS will also be ignored. -V reports the version of ncurses which was used in this program, and exits. The options are as follows: -x do not attempt to clear the terminal's scrollback buffer using the extended E3 capability. HISTORY top A clear command appeared in 2.79BSD dated February 24, 1979. Later that was provided in Unix 8th edition (1985). AT&T adapted a different BSD program (tset) to make a new command (tput), and used this to replace the clear command with a shell script which calls tput clear, e.g., /usr/bin/tput ${1:+-T$1} clear 2> /dev/null exit In 1989, when Keith Bostic revised the BSD tput command to make it similar to the AT&T tput, he added a shell script for the clear command: exec tput clear The remainder of the script in each case is a copyright notice. The ncurses clear command began in 1995 by adapting the original BSD clear command (with terminfo, of course). The E3 extension came later: In June 1999, xterm provided an extension to the standard control sequence for clearing the screen. Rather than clearing just the visible part of the screen using printf '\033[2J' one could clear the scrollback using printf '\033[3J' This is documented in XTerm Control Sequences as a feature originating with xterm. A few other terminal developers adopted the feature, e.g., PuTTY in 2006. In April 2011, a Red Hat developer submitted a patch to the Linux kernel, modifying its console driver to do the same thing. The Linux change, part of the 3.0 release, did not mention xterm, although it was cited in the Red Hat bug report (#683733) which led to the change. Again, a few other terminal developers adopted the feature. But the next relevant step was a change to the clear program in 2013 to incorporate this extension. In 2013, the E3 extension was overlooked in @TPUT@ with the clear parameter. That was addressed in 2016 by reorganizing @TPUT@ to share its logic with @CLEAR@ and @TSET@. PORTABILITY top Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7 (POSIX.1-2008) nor X/Open Curses Issue 7 documents @TSET@ or @RESET@. The latter documents tput, which could be used to replace this utility either via a shell script or by an alias (such as a symbolic link) to run @TPUT@ as @CLEAR@. SEE ALSO top @TPUT@(1), terminfo(5), xterm(1). This describes ncurses version @NCURSES_MAJOR@.@NCURSES_MINOR@ (patch @NCURSES_PATCH@). COLOPHON top This page is part of the ncurses (new curses) project. Information about the project can be found at https://www.gnu.org/software/ncurses/ncurses.html. If you have a bug report for this manual page, send it to bug-ncurses-request@gnu.org. This page was obtained from the project's upstream Git mirror of the CVS repository https://github.com/mirror/ncurses.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-03-12.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org @CLEAR@(1) Pages that refer to this page: setterm(1), user_caps(5) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Clears the terminal screen. Bash Command:<START>clear<END>

Close the master SSH control socket "my-ctrl-socket" to "jm@sampledomain.com"

ssh -S my-ctrl-socket -O exit jm@sampledomain.com

['exit', 'ssh']

Output a Bash command to accomplish the following task. Task: Close the master SSH control socket "my-ctrl-socket" to "jm@sampledomain.com" Bash Command:<START>ssh -S my-ctrl-socket -O exit jm@sampledomain.com<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # exit\n\n> Exit the shell.\n> More information: <https://manned.org/exit.1posix>.\n\n- Exit with the exit status of the most recently executed command:\n\n`exit`\n\n- Exit with a specific exit status:\n\n`exit {{exit_code}}`\n # ssh\n\n> Secure Shell is a protocol used to securely log onto remote systems.\n> It can be used for logging or executing commands on a remote server.\n> More information: <https://man.openbsd.org/ssh>.\n\n- Connect to a remote server:\n\n`ssh {{username}}@{{remote_host}}`\n\n- Connect to a remote server with a specific identity (private key):\n\n`ssh -i {{path/to/key_file}} {{username}}@{{remote_host}}`\n\n- Connect to a remote server using a specific [p]ort:\n\n`ssh {{username}}@{{remote_host}} -p {{2222}}`\n\n- Run a command on a remote server with a [t]ty allocation allowing interaction with the remote command:\n\n`ssh {{username}}@{{remote_host}} -t {{command}} {{command_arguments}}`\n\n- SSH tunneling: [D]ynamic port forwarding (SOCKS proxy on `localhost:1080`):\n\n`ssh -D {{1080}} {{username}}@{{remote_host}}`\n\n- SSH tunneling: Forward a specific port (`localhost:9999` to `example.org:80`) along with disabling pseudo-[T]ty allocation and executio[N] of remote commands:\n\n`ssh -L {{9999}}:{{example.org}}:{{80}} -N -T {{username}}@{{remote_host}}`\n\n- SSH [J]umping: Connect through a jumphost to a remote server (Multiple jump hops may be specified separated by comma characters):\n\n`ssh -J {{username}}@{{jump_host}} {{username}}@{{remote_host}}`\n\n- Agent forwarding: Forward the authentication information to the remote machine (see `man ssh_config` for available options):\n\n`ssh -A {{username}}@{{remote_host}}`\n Task: Close the master SSH control socket "my-ctrl-socket" to "jm@sampledomain.com" Bash Command:<START>ssh -S my-ctrl-socket -O exit jm@sampledomain.com<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: exit(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training exit(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT EXIT(1P) POSIX Programmer's Manual EXIT(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top exit cause the shell to exit SYNOPSIS top exit [n] DESCRIPTION top The exit utility shall cause the shell to exit from its current execution environment with the exit status specified by the unsigned decimal integer n. If the current execution environment is a subshell environment, the shell shall exit from the subshell environment with the specified exit status and continue in the environment from which that subshell environment was invoked; otherwise, the shell utility shall terminate with the specified exit status. If n is specified, but its value is not between 0 and 255 inclusively, the exit status is undefined. A trap on EXIT shall be executed before the shell terminates, except when the exit utility is invoked in that trap itself, in which case the shell shall exit immediately. OPTIONS top None. OPERANDS top See the DESCRIPTION. STDIN top Not used. INPUT FILES top None. ENVIRONMENT VARIABLES top None. ASYNCHRONOUS EVENTS top Default. STDOUT top Not used. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top None. EXTENDED DESCRIPTION top None. EXIT STATUS top The exit status shall be n, if specified, except that the behavior is unspecified if n is not an unsigned decimal integer or is greater than 255. Otherwise, the value shall be the exit value of the last command executed, or zero if no command was executed. When exit is executed in a trap action, the last command is considered to be the command that executed immediately preceding the trap action. CONSEQUENCES OF ERRORS top Default. The following sections are informative. APPLICATION USAGE top None. EXAMPLES top Exit with a true value: exit 0 Exit with a false value: exit 1 Propagate error handling from within a subshell: ( command1 || exit 1 command2 || exit 1 exec command3 ) > outputfile || exit 1 echo "outputfile created successfully" RATIONALE top As explained in other sections, certain exit status values have been reserved for special uses and should be used by applications only for those purposes: 126 A file to be executed was found, but it was not an executable utility. 127 A utility to be executed was not found. >128 A command was interrupted by a signal. The behavior of exit when given an invalid argument or unknown option is unspecified, because of differing practices in the various historical implementations. A value larger than 255 might be truncated by the shell, and be unavailable even to a parent process that uses waitid() to get the full exit value. It is recommended that implementations that detect any usage error should cause a non-zero exit status (or, if the shell is interactive and the error does not cause the shell to abort, store a non-zero value in "$?"), but even this was not done historically in all shells. FUTURE DIRECTIONS top None. SEE ALSO top Section 2.14, Special Built-In Utilities COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 EXIT(1P) Pages that refer to this page: return(1p), sh(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. ssh(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training ssh(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHENTICATION | ESCAPE CHARACTERS | TCP FORWARDING | X11 FORWARDING | VERIFYING HOST KEYS | SSH-BASED VIRTUAL PRIVATE NETWORKS | ENVIRONMENT | FILES | EXIT STATUS | SEE ALSO | STANDARDS | AUTHORS | COLOPHON SSH(1) General Commands Manual SSH(1) NAME top ssh OpenSSH remote login client SYNOPSIS top ssh [-46AaCfGgKkMNnqsTtVvXxYy] [-B bind_interface] [-b bind_address] [-c cipher_spec] [-D [bind_address:]port] [-E log_file] [-e escape_char] [-F configfile] [-I pkcs11] [-i identity_file] [-J destination] [-L address] [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-P tag] [-p port] [-R address] [-S ctl_path] [-W host:port] [-w local_tun[:remote_tun]] destination [command [argument ...]] [-Q query_option] DESCRIPTION top (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine. It is intended to provide secure encrypted communications between two untrusted hosts over an insecure network. X11 connections, arbitrary TCP ports and Unix-domain sockets can also be forwarded over the secure channel. connects and logs into the specified destination, which may be specified as either [user@]hostname or a URI of the form ssh://[user@]hostname[:port]. The user must prove their identity to the remote machine using one of several methods (see below). If a command is specified, it will be executed on the remote host instead of a login shell. A complete command line may be specified as command, or it may have additional arguments. If supplied, the arguments will be appended to the command, separated by spaces, before it is sent to the server to be executed. The options are as follows: -4 Forces to use IPv4 addresses only. -6 Forces to use IPv6 addresses only. -A Enables forwarding of connections from an authentication agent such as ssh-agent(1). This can also be specified on a per-host basis in a configuration file. Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the agent's Unix-domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. A safer alternative may be to use a jump host (see -J). -a Disables forwarding of the authentication agent connection. -B bind_interface Bind to the address of bind_interface before attempting to connect to the destination host. This is only useful on systems with more than one address. -b bind_address Use bind_address on the local machine as the source address of the connection. Only useful on systems with more than one address. -C Requests compression of all data (including stdin, stdout, stderr, and data for forwarded X11, TCP and Unix-domain connections). The compression algorithm is the same used by gzip(1). Compression is desirable on modem lines and other slow connections, but will only slow down things on fast networks. The default value can be set on a host-by-host basis in the configuration files; see the Compression option in ssh_config(5). -c cipher_spec Selects the cipher specification for encrypting the session. cipher_spec is a comma-separated list of ciphers listed in order of preference. See the Ciphers keyword in ssh_config(5) for more information. -D [bind_address:]port Specifies a local dynamic application-level port forwarding. This works by allocating a socket to listen to port on the local side, optionally bound to the specified bind_address. Whenever a connection is made to this port, the connection is forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. Currently the SOCKS4 and SOCKS5 protocols are supported, and will act as a SOCKS server. Only root can forward privileged ports. Dynamic port forwardings can also be specified in the configuration file. IPv6 addresses can be specified by enclosing the address in square brackets. Only the superuser can forward privileged ports. By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address of localhost indicates that the listening port be bound for local use only, while an empty address or * indicates that the port should be available from all interfaces. -E log_file Append debug logs to log_file instead of standard error. -e escape_char Sets the escape character for sessions with a pty (default: ~). The escape character is only recognized at the beginning of a line. The escape character followed by a dot (.) closes the connection; followed by control-Z suspends the connection; and followed by itself sends the escape character once. Setting the character to none disables any escapes and makes the session fully transparent. -F configfile Specifies an alternative per-user configuration file. If a configuration file is given on the command line, the system-wide configuration file (/etc/ssh/ssh_config) will be ignored. The default for the per-user configuration file is ~/.ssh/config. If set to none, no configuration files will be read. -f Requests to go to background just before command execution. This is useful if is going to ask for passwords or passphrases, but the user wants it in the background. This implies -n. The recommended way to start X11 programs at a remote site is with something like ssh -f host xterm. If the ExitOnForwardFailure configuration option is set to yes, then a client started with -f will wait for all remote port forwards to be successfully established before placing itself in the background. Refer to the description of ForkAfterAuthentication in ssh_config(5) for details. -G Causes to print its configuration after evaluating Host and Match blocks and exit. -g Allows remote hosts to connect to local forwarded ports. If used on a multiplexed connection, then this option must be specified on the master process. -I pkcs11 Specify the PKCS#11 shared library should use to communicate with a PKCS#11 token providing keys for user authentication. -i identity_file Selects a file from which the identity (private key) for public key authentication is read. You can also specify a public key file to use the corresponding private key that is loaded in ssh-agent(1) when the private key file is not present locally. The default is ~/.ssh/id_rsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ecdsa_sk, ~/.ssh/id_ed25519, ~/.ssh/id_ed25519_sk and ~/.ssh/id_dsa. Identity files may also be specified on a per-host basis in the configuration file. It is possible to have multiple -i options (and multiple identities specified in configuration files). If no certificates have been explicitly specified by the CertificateFile directive, will also try to load certificate information from the filename obtained by appending -cert.pub to identity filenames. -J destination Connect to the target host by first making an connection to the jump host described by destination and then establishing a TCP forwarding to the ultimate destination from there. Multiple jump hops may be specified separated by comma characters. This is a shortcut to specify a ProxyJump configuration directive. Note that configuration directives supplied on the command-line generally apply to the destination host and not any specified jump hosts. Use ~/.ssh/config to specify configuration for jump hosts. -K Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI credentials to the server. -k Disables forwarding (delegation) of GSSAPI credentials to the server. -L [bind_address:]port:host:hostport -L [bind_address:]port:remote_socket -L local_socket:host:hostport -L local_socket:remote_socket Specifies that connections to the given TCP port or Unix socket on the local (client) host are to be forwarded to the given host and port, or Unix socket, on the remote side. This works by allocating a socket to listen to either a TCP port on the local side, optionally bound to the specified bind_address, or to a Unix socket. Whenever a connection is made to the local port or socket, the connection is forwarded over the secure channel, and a connection is made to either host port hostport, or the Unix socket remote_socket, from the remote machine. Port forwardings can also be specified in the configuration file. Only the superuser can forward privileged ports. IPv6 addresses can be specified by enclosing the address in square brackets. By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address of localhost indicates that the listening port be bound for local use only, while an empty address or * indicates that the port should be available from all interfaces. -l login_name Specifies the user to log in as on the remote machine. This also may be specified on a per-host basis in the configuration file. -M Places the client into master mode for connection sharing. Multiple -M options places into master mode but with confirmation required using ssh-askpass(1) before each operation that changes the multiplexing state (e.g. opening a new session). Refer to the description of ControlMaster in ssh_config(5) for details. -m mac_spec A comma-separated list of MAC (message authentication code) algorithms, specified in order of preference. See the MACs keyword in ssh_config(5) for more information. -N Do not execute a remote command. This is useful for just forwarding ports. Refer to the description of SessionType in ssh_config(5) for details. -n Redirects stdin from /dev/null (actually, prevents reading from stdin). This must be used when is run in the background. A common trick is to use this to run X11 programs on a remote machine. For example, ssh -n shadows.cs.hut.fi emacs & will start an emacs on shadows.cs.hut.fi, and the X11 connection will be automatically forwarded over an encrypted channel. The program will be put in the background. (This does not work if needs to ask for a password or passphrase; see also the -f option.) Refer to the description of StdinNull in ssh_config(5) for details. -O ctl_cmd Control an active connection multiplexing master process. When the -O option is specified, the ctl_cmd argument is interpreted and passed to the master process. Valid commands are: check (check that the master process is running), forward (request forwardings without command execution), cancel (cancel forwardings), exit (request the master to exit), and stop (request the master to stop accepting further multiplexing requests). -o option Can be used to give options in the format used in the configuration file. This is useful for specifying options for which there is no separate command-line flag. For full details of the options listed below, and their possible values, see ssh_config(5). AddKeysToAgent AddressFamily BatchMode BindAddress CanonicalDomains CanonicalizeFallbackLocal CanonicalizeHostname CanonicalizeMaxDots CanonicalizePermittedCNAMEs CASignatureAlgorithms CertificateFile CheckHostIP Ciphers ClearAllForwardings Compression ConnectionAttempts ConnectTimeout ControlMaster ControlPath ControlPersist DynamicForward EnableEscapeCommandline EscapeChar ExitOnForwardFailure FingerprintHash ForkAfterAuthentication ForwardAgent ForwardX11 ForwardX11Timeout ForwardX11Trusted GatewayPorts GlobalKnownHostsFile GSSAPIAuthentication GSSAPIDelegateCredentials HashKnownHosts Host HostbasedAcceptedAlgorithms HostbasedAuthentication HostKeyAlgorithms HostKeyAlias Hostname IdentitiesOnly IdentityAgent IdentityFile IPQoS KbdInteractiveAuthentication KbdInteractiveDevices KexAlgorithms KnownHostsCommand LocalCommand LocalForward LogLevel MACs Match NoHostAuthenticationForLocalhost NumberOfPasswordPrompts PasswordAuthentication PermitLocalCommand PermitRemoteOpen PKCS11Provider Port PreferredAuthentications ProxyCommand ProxyJump ProxyUseFdpass PubkeyAcceptedAlgorithms PubkeyAuthentication RekeyLimit RemoteCommand RemoteForward RequestTTY RequiredRSASize SendEnv ServerAliveInterval ServerAliveCountMax SessionType SetEnv StdinNull StreamLocalBindMask StreamLocalBindUnlink StrictHostKeyChecking TCPKeepAlive Tunnel TunnelDevice UpdateHostKeys User UserKnownHostsFile VerifyHostKeyDNS VisualHostKey XAuthLocation -P tag Specify a tag name that may be used to select configuration in ssh_config(5). Refer to the Tag and Match keywords in ssh_config(5) for more information. -p port Port to connect to on the remote host. This can be specified on a per-host basis in the configuration file. -Q query_option Queries for the algorithms supported by one of the following features: cipher (supported symmetric ciphers), cipher-auth (supported symmetric ciphers that support authenticated encryption), help (supported query terms for use with the -Q flag), mac (supported message integrity codes), kex (key exchange algorithms), key (key types), key-ca-sign (valid CA signature algorithms for certificates), key-cert (certificate key types), key-plain (non-certificate key types), key-sig (all key types and signature algorithms), protocol-version (supported SSH protocol versions), and sig (supported signature algorithms). Alternatively, any keyword from ssh_config(5) or sshd_config(5) that takes an algorithm list may be used as an alias for the corresponding query_option. -q Quiet mode. Causes most warning and diagnostic messages to be suppressed. -R [bind_address:]port:host:hostport -R [bind_address:]port:local_socket -R remote_socket:host:hostport -R remote_socket:local_socket -R [bind_address:]port Specifies that connections to the given TCP port or Unix socket on the remote (server) host are to be forwarded to the local side. This works by allocating a socket to listen to either a TCP port or to a Unix socket on the remote side. Whenever a connection is made to this port or Unix socket, the connection is forwarded over the secure channel, and a connection is made from the local machine to either an explicit destination specified by host port hostport, or local_socket, or, if no explicit destination was specified, will act as a SOCKS 4/5 proxy and forward connections to the destinations requested by the remote SOCKS client. Port forwardings can also be specified in the configuration file. Privileged ports can be forwarded only when logging in as root on the remote machine. IPv6 addresses can be specified by enclosing the address in square brackets. By default, TCP listening sockets on the server will be bound to the loopback interface only. This may be overridden by specifying a bind_address. An empty bind_address, or the address *, indicates that the remote socket should listen on all interfaces. Specifying a remote bind_address will only succeed if the server's GatewayPorts option is enabled (see sshd_config(5)). If the port argument is 0, the listen port will be dynamically allocated on the server and reported to the client at run time. When used together with -O forward, the allocated port will be printed to the standard output. -S ctl_path Specifies the location of a control socket for connection sharing, or the string none to disable connection sharing. Refer to the description of ControlPath and ControlMaster in ssh_config(5) for details. -s May be used to request invocation of a subsystem on the remote system. Subsystems facilitate the use of SSH as a secure transport for other applications (e.g. sftp(1)). The subsystem is specified as the remote command. Refer to the description of SessionType in ssh_config(5) for details. -T Disable pseudo-terminal allocation. -t Force pseudo-terminal allocation. This can be used to execute arbitrary screen-based programs on a remote machine, which can be very useful, e.g. when implementing menu services. Multiple -t options force tty allocation, even if has no local tty. -V Display the version number and exit. -v Verbose mode. Causes to print debugging messages about its progress. This is helpful in debugging connection, authentication, and configuration problems. Multiple -v options increase the verbosity. The maximum is 3. -W host:port Requests that standard input and output on the client be forwarded to host on port over the secure channel. Implies -N, -T, ExitOnForwardFailure and ClearAllForwardings, though these can be overridden in the configuration file or using -o command line options. -w local_tun[:remote_tun] Requests tunnel device forwarding with the specified tun(4) devices between the client (local_tun) and the server (remote_tun). The devices may be specified by numerical ID or the keyword any, which uses the next available tunnel device. If remote_tun is not specified, it defaults to any. See also the Tunnel and TunnelDevice directives in ssh_config(5). If the Tunnel directive is unset, it will be set to the default tunnel mode, which is point-to-point. If a different Tunnel forwarding mode it desired, then it should be specified before -w. -X Enables X11 forwarding. This can also be specified on a per-host basis in a configuration file. X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user's X authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring. For this reason, X11 forwarding is subjected to X11 SECURITY extension restrictions by default. Refer to the -Y option and the ForwardX11Trusted directive in ssh_config(5) for more information. -x Disables X11 forwarding. -Y Enables trusted X11 forwarding. Trusted X11 forwardings are not subjected to the X11 SECURITY extension controls. -y Send log information using the syslog(3) system module. By default this information is sent to stderr. may additionally obtain configuration data from a per-user configuration file and a system-wide configuration file. The file format and configuration options are described in ssh_config(5). AUTHENTICATION top The OpenSSH SSH client supports SSH protocol 2. The methods available for authentication are: GSSAPI-based authentication, host-based authentication, public key authentication, keyboard-interactive authentication, and password authentication. Authentication methods are tried in the order specified above, though PreferredAuthentications can be used to change the default order. Host-based authentication works as follows: If the machine the user logs in from is listed in /etc/hosts.equiv or /etc/shosts.equiv on the remote machine, the user is non-root and the user names are the same on both sides, or if the files ~/.rhosts or ~/.shosts exist in the user's home directory on the remote machine and contain a line containing the name of the client machine and the name of the user on that machine, the user is considered for login. Additionally, the server must be able to verify the client's host key (see the description of /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts, below) for login to be permitted. This authentication method closes security holes due to IP spoofing, DNS spoofing, and routing spoofing. [Note to the administrator: /etc/hosts.equiv, ~/.rhosts, and the rlogin/rsh protocol in general, are inherently insecure and should be disabled if security is desired.] Public key authentication works as follows: The scheme is based on public-key cryptography, using cryptosystems where encryption and decryption are done using separate keys, and it is unfeasible to derive the decryption key from the encryption key. The idea is that each user creates a public/private key pair for authentication purposes. The server knows the public key, and only the user knows the private key. implements public key authentication protocol automatically, using one of the DSA, ECDSA, Ed25519 or RSA algorithms. The HISTORY section of ssl(8) contains a brief discussion of the DSA and RSA algorithms. The file ~/.ssh/authorized_keys lists the public keys that are permitted for logging in. When the user logs in, the program tells the server which key pair it would like to use for authentication. The client proves that it has access to the private key and the server checks that the corresponding public key is authorized to accept the account. The server may inform the client of errors that prevented public key authentication from succeeding after authentication completes using a different method. These may be viewed by increasing the LogLevel to DEBUG or higher (e.g. by using the -v flag). The user creates their key pair by running ssh-keygen(1). This stores the private key in ~/.ssh/id_dsa (DSA), ~/.ssh/id_ecdsa (ECDSA), ~/.ssh/id_ecdsa_sk (authenticator-hosted ECDSA), ~/.ssh/id_ed25519 (Ed25519), ~/.ssh/id_ed25519_sk (authenticator- hosted Ed25519), or ~/.ssh/id_rsa (RSA) and stores the public key in ~/.ssh/id_dsa.pub (DSA), ~/.ssh/id_ecdsa.pub (ECDSA), ~/.ssh/id_ecdsa_sk.pub (authenticator-hosted ECDSA), ~/.ssh/id_ed25519.pub (Ed25519), ~/.ssh/id_ed25519_sk.pub (authenticator-hosted Ed25519), or ~/.ssh/id_rsa.pub (RSA) in the user's home directory. The user should then copy the public key to ~/.ssh/authorized_keys in their home directory on the remote machine. The authorized_keys file corresponds to the conventional ~/.rhosts file, and has one key per line, though the lines can be very long. After this, the user can log in without giving the password. A variation on public key authentication is available in the form of certificate authentication: instead of a set of public/private keys, signed certificates are used. This has the advantage that a single trusted certification authority can be used in place of many public/private keys. See the CERTIFICATES section of ssh-keygen(1) for more information. The most convenient way to use public key or certificate authentication may be with an authentication agent. See ssh-agent(1) and (optionally) the AddKeysToAgent directive in ssh_config(5) for more information. Keyboard-interactive authentication works as follows: The server sends an arbitrary "challenge" text and prompts for a response, possibly multiple times. Examples of keyboard-interactive authentication include BSD Authentication (see login.conf(5)) and PAM (some non-OpenBSD systems). Finally, if other authentication methods fail, prompts the user for a password. The password is sent to the remote host for checking; however, since all communications are encrypted, the password cannot be seen by someone listening on the network. automatically maintains and checks a database containing identification for all hosts it has ever been used with. Host keys are stored in ~/.ssh/known_hosts in the user's home directory. Additionally, the file /etc/ssh/ssh_known_hosts is automatically checked for known hosts. Any new hosts are automatically added to the user's file. If a host's identification ever changes, warns about this and disables password authentication to prevent server spoofing or man-in-the- middle attacks, which could otherwise be used to circumvent the encryption. The StrictHostKeyChecking option can be used to control logins to machines whose host key is not known or has changed. When the user's identity has been accepted by the server, the server either executes the given command in a non-interactive session or, if no command has been specified, logs into the machine and gives the user a normal shell as an interactive session. All communication with the remote command or shell will be automatically encrypted. If an interactive session is requested, by default will only request a pseudo-terminal (pty) for interactive sessions when the client has one. The flags -T and -t can be used to override this behaviour. If a pseudo-terminal has been allocated, the user may use the escape characters noted below. If no pseudo-terminal has been allocated, the session is transparent and can be used to reliably transfer binary data. On most systems, setting the escape character to none will also make the session transparent even if a tty is used. The session terminates when the command or shell on the remote machine exits and all X11 and TCP connections have been closed. ESCAPE CHARACTERS top When a pseudo-terminal has been requested, supports a number of functions through the use of an escape character. A single tilde character can be sent as ~~ or by following the tilde by a character other than those described below. The escape character must always follow a newline to be interpreted as special. The escape character can be changed in configuration files using the EscapeChar configuration directive or on the command line by the -e option. The supported escapes (assuming the default ~) are: ~. Disconnect. ~^Z Background . ~# List forwarded connections. ~& Background at logout when waiting for forwarded connection / X11 sessions to terminate. ~? Display a list of escape characters. ~B Send a BREAK to the remote system (only useful if the peer supports it). ~C Open command line. Currently this allows the addition of port forwardings using the -L, -R and -D options (see above). It also allows the cancellation of existing port-forwardings with -KL[bind_address:]port for local, -KR[bind_address:]port for remote and -KD[bind_address:]port for dynamic port-forwardings. !command allows the user to execute a local command if the PermitLocalCommand option is enabled in ssh_config(5). Basic help is available, using the -h option. ~R Request rekeying of the connection (only useful if the peer supports it). ~V Decrease the verbosity (LogLevel) when errors are being written to stderr. ~v Increase the verbosity (LogLevel) when errors are being written to stderr. TCP FORWARDING top Forwarding of arbitrary TCP connections over a secure channel can be specified either on the command line or in a configuration file. One possible application of TCP forwarding is a secure connection to a mail server; another is going through firewalls. In the example below, we look at encrypting communication for an IRC client, even though the IRC server it connects to does not directly support encrypted communication. This works as follows: the user connects to the remote host using , specifying the ports to be used to forward the connection. After that it is possible to start the program locally, and will encrypt and forward the connection to the remote server. The following example tunnels an IRC session from the client to an IRC server at server.example.com, joining channel #users, nickname pinky, using the standard IRC port, 6667: $ ssh -f -L 6667:localhost:6667 server.example.com sleep 10 $ irc -c '#users' pinky IRC/127.0.0.1 The -f option backgrounds and the remote command sleep 10 is specified to allow an amount of time (10 seconds, in the example) to start the program which is going to use the tunnel. If no connections are made within the time specified, will exit. X11 FORWARDING top If the ForwardX11 variable is set to yes (or see the description of the -X, -x, and -Y options above) and the user is using X11 (the DISPLAY environment variable is set), the connection to the X11 display is automatically forwarded to the remote side in such a way that any X11 programs started from the shell (or command) will go through the encrypted channel, and the connection to the real X server will be made from the local machine. The user should not manually set DISPLAY. Forwarding of X11 connections can be configured on the command line or in configuration files. The DISPLAY value set by will point to the server machine, but with a display number greater than zero. This is normal, and happens because creates a proxy X server on the server machine for forwarding the connections over the encrypted channel. will also automatically set up Xauthority data on the server machine. For this purpose, it will generate a random authorization cookie, store it in Xauthority on the server, and verify that any forwarded connections carry this cookie and replace it by the real cookie when the connection is opened. The real authentication cookie is never sent to the server machine (and no cookies are sent in the plain). If the ForwardAgent variable is set to yes (or see the description of the -A and -a options above) and the user is using an authentication agent, the connection to the agent is automatically forwarded to the remote side. VERIFYING HOST KEYS top When connecting to a server for the first time, a fingerprint of the server's public key is presented to the user (unless the option StrictHostKeyChecking has been disabled). Fingerprints can be determined using ssh-keygen(1): $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key If the fingerprint is already known, it can be matched and the key can be accepted or rejected. If only legacy (MD5) fingerprints for the server are available, the ssh-keygen(1) -E option may be used to downgrade the fingerprint algorithm to match. Because of the difficulty of comparing host keys just by looking at fingerprint strings, there is also support to compare host keys visually, using random art. By setting the VisualHostKey option to yes, a small ASCII graphic gets displayed on every login to a server, no matter if the session itself is interactive or not. By learning the pattern a known server produces, a user can easily find out that the host key has changed when a completely different pattern is displayed. Because these patterns are not unambiguous however, a pattern that looks similar to the pattern remembered only gives a good probability that the host key is the same, not guaranteed proof. To get a listing of the fingerprints along with their random art for all known hosts, the following command line can be used: $ ssh-keygen -lv -f ~/.ssh/known_hosts If the fingerprint is unknown, an alternative method of verification is available: SSH fingerprints verified by DNS. An additional resource record (RR), SSHFP, is added to a zonefile and the connecting client is able to match the fingerprint with that of the key presented. In this example, we are connecting a client to a server, host.example.com. The SSHFP resource records should first be added to the zonefile for host.example.com: $ ssh-keygen -r host.example.com. The output lines will have to be added to the zonefile. To check that the zone is answering fingerprint queries: $ dig -t SSHFP host.example.com Finally the client connects: $ ssh -o "VerifyHostKeyDNS ask" host.example.com [...] Matching host key fingerprint found in DNS. Are you sure you want to continue connecting (yes/no)? See the VerifyHostKeyDNS option in ssh_config(5) for more information. SSH-BASED VIRTUAL PRIVATE NETWORKS top contains support for Virtual Private Network (VPN) tunnelling using the tun(4) network pseudo-device, allowing two networks to be joined securely. The sshd_config(5) configuration option PermitTunnel controls whether the server supports this, and at what level (layer 2 or 3 traffic). The following example would connect client network 10.0.50.0/24 with remote network 10.0.99.0/24 using a point-to-point connection from 10.1.1.1 to 10.1.1.2, provided that the SSH server running on the gateway to the remote network, at 192.168.1.15, allows it. On the client: # ssh -f -w 0:1 192.168.1.15 true # ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252 # route add 10.0.99.0/24 10.1.1.2 On the server: # ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252 # route add 10.0.50.0/24 10.1.1.1 Client access may be more finely tuned via the /root/.ssh/authorized_keys file (see below) and the PermitRootLogin server option. The following entry would permit connections on tun(4) device 1 from user jane and on tun device 2 from user john, if PermitRootLogin is set to forced-commands-only: tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john Since an SSH-based setup entails a fair amount of overhead, it may be more suited to temporary setups, such as for wireless VPNs. More permanent VPNs are better provided by tools such as ipsecctl(8) and isakmpd(8). ENVIRONMENT top will normally set the following environment variables: DISPLAY The DISPLAY variable indicates the location of the X11 server. It is automatically set by to point to a value of the form hostname:n, where hostname indicates the host where the shell runs, and n is an integer 1. uses this special value to forward X11 connections over the secure channel. The user should normally not set DISPLAY explicitly, as that will render the X11 connection insecure (and will require the user to manually copy any required authorization cookies). HOME Set to the path of the user's home directory. LOGNAME Synonym for USER; set for compatibility with systems that use this variable. MAIL Set to the path of the user's mailbox. PATH Set to the default PATH, as specified when compiling . SSH_ASKPASS If needs a passphrase, it will read the passphrase from the current terminal if it was run from a terminal. If does not have a terminal associated with it but DISPLAY and SSH_ASKPASS are set, it will execute the program specified by SSH_ASKPASS and open an X11 window to read the passphrase. This is particularly useful when calling from a .xsession or related script. (Note that on some machines it may be necessary to redirect the input from /dev/null to make this work.) SSH_ASKPASS_REQUIRE Allows further control over the use of an askpass program. If this variable is set to never then will never attempt to use one. If it is set to prefer, then will prefer to use the askpass program instead of the TTY when requesting passwords. Finally, if the variable is set to force, then the askpass program will be used for all passphrase input regardless of whether DISPLAY is set. SSH_AUTH_SOCK Identifies the path of a Unix-domain socket used to communicate with the agent. SSH_CONNECTION Identifies the client and server ends of the connection. The variable contains four space-separated values: client IP address, client port number, server IP address, and server port number. SSH_ORIGINAL_COMMAND This variable contains the original command line if a forced command is executed. It can be used to extract the original arguments. SSH_TTY This is set to the name of the tty (path to the device) associated with the current shell or command. If the current session has no tty, this variable is not set. SSH_TUNNEL Optionally set by sshd(8) to contain the interface names assigned if tunnel forwarding was requested by the client. SSH_USER_AUTH Optionally set by sshd(8), this variable may contain a pathname to a file that lists the authentication methods successfully used when the session was established, including any public keys that were used. TZ This variable is set to indicate the present time zone if it was set when the daemon was started (i.e. the daemon passes the value on to new connections). USER Set to the name of the user logging in. Additionally, reads ~/.ssh/environment, and adds lines of the format VARNAME=value to the environment if the file exists and users are allowed to change their environment. For more information, see the PermitUserEnvironment option in sshd_config(5). FILES top ~/.rhosts This file is used for host-based authentication (see above). On some machines this file may need to be world- readable if the user's home directory is on an NFS partition, because sshd(8) reads it as root. Additionally, this file must be owned by the user, and must not have write permissions for anyone else. The recommended permission for most machines is read/write for the user, and not accessible by others. ~/.shosts This file is used in exactly the same way as .rhosts, but allows host-based authentication without permitting login with rlogin/rsh. ~/.ssh/ This directory is the default location for all user- specific configuration and authentication information. There is no general requirement to keep the entire contents of this directory secret, but the recommended permissions are read/write/execute for the user, and not accessible by others. ~/.ssh/authorized_keys Lists the public keys (DSA, ECDSA, Ed25519, RSA) that can be used for logging in as this user. The format of this file is described in the sshd(8) manual page. This file is not highly sensitive, but the recommended permissions are read/write for the user, and not accessible by others. ~/.ssh/config This is the per-user configuration file. The file format and configuration options are described in ssh_config(5). Because of the potential for abuse, this file must have strict permissions: read/write for the user, and not writable by others. ~/.ssh/environment Contains additional definitions for environment variables; see ENVIRONMENT, above. ~/.ssh/id_dsa ~/.ssh/id_ecdsa ~/.ssh/id_ecdsa_sk ~/.ssh/id_ed25519 ~/.ssh/id_ed25519_sk ~/.ssh/id_rsa Contains the private key for authentication. These files contain sensitive data and should be readable by the user but not accessible by others (read/write/execute). will simply ignore a private key file if it is accessible by others. It is possible to specify a passphrase when generating the key which will be used to encrypt the sensitive part of this file using AES-128. ~/.ssh/id_dsa.pub ~/.ssh/id_ecdsa.pub ~/.ssh/id_ecdsa_sk.pub ~/.ssh/id_ed25519.pub ~/.ssh/id_ed25519_sk.pub ~/.ssh/id_rsa.pub Contains the public key for authentication. These files are not sensitive and can (but need not) be readable by anyone. ~/.ssh/known_hosts Contains a list of host keys for all hosts the user has logged into that are not already in the systemwide list of known host keys. See sshd(8) for further details of the format of this file. ~/.ssh/rc Commands in this file are executed by when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information. /etc/hosts.equiv This file is for host-based authentication (see above). It should only be writable by root. /etc/shosts.equiv This file is used in exactly the same way as hosts.equiv, but allows host-based authentication without permitting login with rlogin/rsh. /etc/ssh/ssh_config Systemwide configuration file. The file format and configuration options are described in ssh_config(5). /etc/ssh/ssh_host_key /etc/ssh/ssh_host_dsa_key /etc/ssh/ssh_host_ecdsa_key /etc/ssh/ssh_host_ed25519_key /etc/ssh/ssh_host_rsa_key These files contain the private parts of the host keys and are used for host-based authentication. /etc/ssh/ssh_known_hosts Systemwide list of known host keys. This file should be prepared by the system administrator to contain the public host keys of all machines in the organization. It should be world-readable. See sshd(8) for further details of the format of this file. /etc/ssh/sshrc Commands in this file are executed by when the user logs in, just before the user's shell (or command) is started. See the sshd(8) manual page for more information. EXIT STATUS top exits with the exit status of the remote command or with 255 if an error occurred. SEE ALSO top scp(1), sftp(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), ssh-keyscan(1), tun(4), ssh_config(5), ssh-keysign(8), sshd(8) STANDARDS top S. Lehtinen and C. Lonvick, The Secure Shell (SSH) Protocol Assigned Numbers, RFC 4250, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Protocol Architecture, RFC 4251, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Authentication Protocol, RFC 4252, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Transport Layer Protocol, RFC 4253, January 2006. T. Ylonen and C. Lonvick, The Secure Shell (SSH) Connection Protocol, RFC 4254, January 2006. J. Schlyter and W. Griffin, Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints, RFC 4255, January 2006. F. Cusack and M. Forssen, Generic Message Exchange Authentication for the Secure Shell Protocol (SSH), RFC 4256, January 2006. J. Galbraith and P. Remaker, The Secure Shell (SSH) Session Channel Break Extension, RFC 4335, January 2006. M. Bellare, T. Kohno, and C. Namprempre, The Secure Shell (SSH) Transport Layer Encryption Modes, RFC 4344, January 2006. B. Harris, Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol, RFC 4345, January 2006. M. Friedl, N. Provos, and W. Simpson, Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol, RFC 4419, March 2006. J. Galbraith and R. Thayer, The Secure Shell (SSH) Public Key File Format, RFC 4716, November 2006. D. Stebila and J. Green, Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer, RFC 5656, December 2009. A. Perrig and D. Song, Hash Visualization: a New Technique to improve Real-World Security, 1999, International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99). AUTHORS top OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re- added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol versions 1.5 and 2.0. COLOPHON top This page is part of the openssh (Portable OpenSSH) project. Information about the project can be found at http://www.openssh.com/portable.html. If you have a bug report for this manual page, see http://www.openssh.com/report.html. This page was obtained from the tarball openssh-9.6p1.tar.gz fetched from http://ftp.eu.openbsd.org/pub/OpenBSD/OpenSSH/portable/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU October 11, 2023 SSH(1) Pages that refer to this page: stap-jupyter(1), systemd-stdio-bridge(1), tar(1), sd_bus_default(3), environment.d(5), proc(5), user@.service(5), pty(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Close the master SSH control socket "my-ctrl-socket" to "jm@sampledomain.com" Bash Command:<START>ssh -S my-ctrl-socket -O exit jm@sampledomain.com<END>

Collapse double slashes in variable "dir" into a single one.

dir="`echo $dir | sed s,//,/,g`"

['sed', 'echo']

Output a Bash command to accomplish the following task. Task: Collapse double slashes in variable "dir" into a single one. Bash Command:<START>dir="`echo $dir | sed s,//,/,g`"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # sed\n\n> Edit text in a scriptable manner.\n> See also: `awk`, `ed`.\n> More information: <https://www.gnu.org/software/sed/manual/sed.html>.\n\n- Replace all `apple` (basic regex) occurrences with `mango` (basic regex) in all input lines and print the result to `stdout`:\n\n`{{command}} | sed 's/apple/mango/g'`\n\n- Replace all `apple` (extended regex) occurrences with `APPLE` (extended regex) in all input lines and print the result to `stdout`:\n\n`{{command}} | sed -E 's/(apple)/\U\1/g'`\n\n- Replace all `apple` (basic regex) occurrences with `mango` (basic regex) in a specific file and overwrite the original file in place:\n\n`sed -i 's/apple/mango/g' {{path/to/file}}`\n\n- Execute a specific script [f]ile and print the result to `stdout`:\n\n`{{command}} | sed -f {{path/to/script.sed}}`\n\n- Print just the first line to `stdout`:\n\n`{{command}} | sed -n '1p'`\n\n- [d]elete the first line of a file:\n\n`sed -i 1d {{path/to/file}}`\n\n- [i]nsert a new line at the first line of a file:\n\n`sed -i '1i\your new line text\' {{path/to/file}}`\n # echo\n\n> Print given arguments.\n> More information: <https://www.gnu.org/software/coreutils/echo>.\n\n- Print a text message. Note: quotes are optional:\n\n`echo "{{Hello World}}"`\n\n- Print a message with environment variables:\n\n`echo "{{My path is $PATH}}"`\n\n- Print a message without the trailing newline:\n\n`echo -n "{{Hello World}}"`\n\n- Append a message to the file:\n\n`echo "{{Hello World}}" >> {{file.txt}}`\n\n- Enable interpretation of backslash escapes (special characters):\n\n`echo -e "{{Column 1\tColumn 2}}"`\n\n- Print the exit status of the last executed command (Note: In Windows Command Prompt and PowerShell the equivalent commands are `echo %errorlevel%` and `$lastexitcode` respectively):\n\n`echo $?`\n Task: Collapse double slashes in variable "dir" into a single one. Bash Command:<START>dir="`echo $dir | sed s,//,/,g`"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: sed(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training sed(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | COMMAND SYNOPSIS | REGULAR EXPRESSIONS | BUGS | AUTHOR | COPYRIGHT | SEE ALSO | COLOPHON SED(1) User Commands SED(1) NAME top sed - stream editor for filtering and transforming text SYNOPSIS top sed [-V] [--version] [--help] [-n] [--quiet] [--silent] [-l N] [--line-length=N] [-u] [--unbuffered] [-E] [-r] [--regexp-extended] [-e script] [--expression=script] [-f script-file] [--file=script-file] [script-if-no-other-script] [file...] DESCRIPTION top Sed is a stream editor. A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline). While in some ways similar to an editor which permits scripted edits (such as ed), sed works by making only one pass over the input(s), and is consequently more efficient. But it is sed's ability to filter text in a pipeline which particularly distinguishes it from other types of editors. -n, --quiet, --silent suppress automatic printing of pattern space --debug annotate program execution -e script, --expression=script add the script to the commands to be executed -f script-file, --file=script-file add the contents of script-file to the commands to be executed --follow-symlinks follow symlinks when processing in place -i[SUFFIX], --in-place[=SUFFIX] edit files in place (makes backup if SUFFIX supplied) -l N, --line-length=N specify the desired line-wrap length for the `l' command --posix disable all GNU extensions. -E, -r, --regexp-extended use extended regular expressions in the script (for portability use POSIX -E). -s, --separate consider files as separate rather than as a single, continuous long stream. --sandbox operate in sandbox mode (disable e/r/w commands). -u, --unbuffered load minimal amounts of data from the input files and flush the output buffers more often -z, --null-data separate lines by NUL characters --help display this help and exit --version output version information and exit If no -e, --expression, -f, or --file option is given, then the first non-option argument is taken as the sed script to interpret. All remaining arguments are names of input files; if no input files are specified, then the standard input is read. GNU sed home page: <https://www.gnu.org/software/sed/>. General help using GNU software: <https://www.gnu.org/gethelp/>. E-mail bug reports to: <bug-sed@gnu.org>. COMMAND SYNOPSIS top This is just a brief synopsis of sed commands to serve as a reminder to those who already know sed; other documentation (such as the texinfo document) must be consulted for fuller descriptions. Zero-address ``commands'' : label Label for b and t commands. #comment The comment extends until the next newline (or the end of a -e script fragment). } The closing bracket of a { } block. Zero- or One- address commands = Print the current line number. a \ text Append text, which has each embedded newline preceded by a backslash. i \ text Insert text, which has each embedded newline preceded by a backslash. q [exit-code] Immediately quit the sed script without processing any more input, except that if auto-print is not disabled the current pattern space will be printed. The exit code argument is a GNU extension. Q [exit-code] Immediately quit the sed script without processing any more input. This is a GNU extension. r filename Append text read from filename. R filename Append a line read from filename. Each invocation of the command reads a line from the file. This is a GNU extension. Commands which accept address ranges { Begin a block of commands (end with a }). b label Branch to label; if label is omitted, branch to end of script. c \ text Replace the selected lines with text, which has each embedded newline preceded by a backslash. d Delete pattern space. Start next cycle. D If pattern space contains no newline, start a normal new cycle as if the d command was issued. Otherwise, delete text in the pattern space up to the first newline, and restart cycle with the resultant pattern space, without reading a new line of input. h H Copy/append pattern space to hold space. g G Copy/append hold space to pattern space. l List out the current line in a ``visually unambiguous'' form. l width List out the current line in a ``visually unambiguous'' form, breaking it at width characters. This is a GNU extension. n N Read/append the next line of input into the pattern space. p Print the current pattern space. P Print up to the first embedded newline of the current pattern space. s/regexp/replacement/ Attempt to match regexp against the pattern space. If successful, replace that portion matched with replacement. The replacement may contain the special character & to refer to that portion of the pattern space which matched, and the special escapes \1 through \9 to refer to the corresponding matching sub-expressions in the regexp. t label If a s/// has done a successful substitution since the last input line was read and since the last t or T command, then branch to label; if label is omitted, branch to end of script. T label If no s/// has done a successful substitution since the last input line was read and since the last t or T command, then branch to label; if label is omitted, branch to end of script. This is a GNU extension. w filename Write the current pattern space to filename. W filename Write the first line of the current pattern space to filename. This is a GNU extension. x Exchange the contents of the hold and pattern spaces. y/source/dest/ Transliterate the characters in the pattern space which appear in source to the corresponding character in dest. Addresses Sed commands can be given with no addresses, in which case the command will be executed for all input lines; with one address, in which case the command will only be executed for input lines which match that address; or with two addresses, in which case the command will be executed for all input lines which match the inclusive range of lines starting from the first address and continuing to the second address. Three things to note about address ranges: the syntax is addr1,addr2 (i.e., the addresses are separated by a comma); the line which addr1 matched will always be accepted, even if addr2 selects an earlier line; and if addr2 is a regexp, it will not be tested against the line that addr1 matched. After the address (or address-range), and before the command, a ! may be inserted, which specifies that the command shall only be executed if the address (or address-range) does not match. The following address types are supported: number Match only the specified line number (which increments cumulatively across files, unless the -s option is specified on the command line). first~step Match every step'th line starting with line first. For example, ``sed -n 1~2p'' will print all the odd-numbered lines in the input stream, and the address 2~5 will match every fifth line, starting with the second. first can be zero; in this case, sed operates as if it were equal to step. (This is an extension.) $ Match the last line. /regexp/ Match lines matching the regular expression regexp. Matching is performed on the current pattern space, which can be modified with commands such as ``s///''. \cregexpc Match lines matching the regular expression regexp. The c may be any character. GNU sed also supports some special 2-address forms: 0,addr2 Start out in "matched first address" state, until addr2 is found. This is similar to 1,addr2, except that if addr2 matches the very first line of input the 0,addr2 form will be at the end of its range, whereas the 1,addr2 form will still be at the beginning of its range. This works only when addr2 is a regular expression. addr1,+N Will match addr1 and the N lines following addr1. addr1,~N Will match addr1 and the lines following addr1 until the next line whose input line number is a multiple of N. REGULAR EXPRESSIONS top POSIX.2 BREs should be supported, but they aren't completely because of performance problems. The \n sequence in a regular expression matches the newline character, and similarly for \a, \t, and other sequences. The -E option switches to using extended regular expressions instead; it has been supported for years by GNU sed, and is now included in POSIX. BUGS top E-mail bug reports to bug-sed@gnu.org. Also, please include the output of ``sed --version'' in the body of your report if at all possible. AUTHOR top Written by Jay Fenlason, Tom Lord, Ken Pizzini, Paolo Bonzini, Jim Meyering, and Assaf Gordon. This sed program was built with SELinux support. SELinux is enabled on this system. GNU sed home page: <https://www.gnu.org/software/sed/>. General help using GNU software: <https://www.gnu.org/gethelp/>. E-mail bug reports to: <bug-sed@gnu.org>. COPYRIGHT top Copyright 2022 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top awk(1), ed(1), grep(1), tr(1), perlre(1), sed.info, any of various books on sed, the sed FAQ (http://sed.sf.net/grabbag/tutorials/sedfaq.txt), http://sed.sf.net/grabbag/. The full documentation for sed is maintained as a Texinfo manual. If the info and sed programs are properly installed at your site, the command info sed should give you access to the complete manual. COLOPHON top This page is part of the sed (stream-oriented editor) project. Information about the project can be found at http://www.gnu.org/software/sed/. If you have a bug report for this manual page, send it to bug-sed@gnu.org. This page was obtained from the tarball sed-4.9.tar.gz fetched from https://www.gnu.org/software/sed/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU sed 4.9 November 2022 SED(1) Pages that refer to this page: gawk(1), grep(1), iostat2pcp(1), pmdaopenmetrics(1), pmlogrewrite(1), sheet2pcp(1), cpuset(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. echo(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training echo(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON ECHO(1) User Commands ECHO(1) NAME top echo - display a line of text SYNOPSIS top echo [SHORT-OPTION]... [STRING]... echo LONG-OPTION DESCRIPTION top Echo the STRING(s) to standard output. -n do not output the trailing newline -e enable interpretation of backslash escapes -E disable interpretation of backslash escapes (default) --help display this help and exit --version output version information and exit If -e is in effect, the following sequences are recognized: \\ backslash \a alert (BEL) \b backspace \c produce no further output \e escape \f form feed \n new line \r carriage return \t horizontal tab \v vertical tab \0NNN byte with octal value NNN (1 to 3 digits) \xHH byte with hexadecimal value HH (1 to 2 digits) NOTE: your shell may have its own version of echo, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports. NOTE: printf(1) is a preferred alternative, which does not have issues outputting option-like strings. AUTHOR top Written by Brian Fox and Chet Ramey. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top printf(1) Full documentation <https://www.gnu.org/software/coreutils/echo> or available locally via: info '(coreutils) echo invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 ECHO(1) Pages that refer to this page: ldapcompare(1), systemd-ask-password(1), systemd-run(1), cpuset(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Collapse double slashes in variable "dir" into a single one. Bash Command:<START>dir="`echo $dir | sed s,//,/,g`"<END>

Combine every two lines of standard input

paste -d "" - -

['paste']

Output a Bash command to accomplish the following task. Task: Combine every two lines of standard input Bash Command:<START>paste -d "" - -<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # paste\n\n> Merge lines of files.\n> More information: <https://www.gnu.org/software/coreutils/paste>.\n\n- Join all the lines into a single line, using TAB as delimiter:\n\n`paste -s {{path/to/file}}`\n\n- Join all the lines into a single line, using the specified delimiter:\n\n`paste -s -d {{delimiter}} {{path/to/file}}`\n\n- Merge two files side by side, each in its column, using TAB as delimiter:\n\n`paste {{file1}} {{file2}}`\n\n- Merge two files side by side, each in its column, using the specified delimiter:\n\n`paste -d {{delimiter}} {{file1}} {{file2}}`\n\n- Merge two files, with lines added alternatively:\n\n`paste -d '\n' {{file1}} {{file2}}`\n Task: Combine every two lines of standard input Bash Command:<START>paste -d "" - -<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: paste(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training paste(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON PASTE(1) User Commands PASTE(1) NAME top paste - merge lines of files SYNOPSIS top paste [OPTION]... [FILE]... DESCRIPTION top Write lines consisting of the sequentially corresponding lines from each FILE, separated by TABs, to standard output. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. -d, --delimiters=LIST reuse characters from LIST instead of TABs -s, --serial paste one file at a time instead of in parallel -z, --zero-terminated line delimiter is NUL, not newline --help display this help and exit --version output version information and exit AUTHOR top Written by David M. Ihnat and David MacKenzie. REPORTING BUGS top GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top Full documentation <https://www.gnu.org/software/coreutils/paste> or available locally via: info '(coreutils) paste invocation' COLOPHON top This page is part of the coreutils (basic file, shell and text manipulation utilities) project. Information about the project can be found at http://www.gnu.org/software/coreutils/. If you have a bug report for this manual page, see http://www.gnu.org/software/coreutils/. This page was obtained from the tarball coreutils-9.4.tar.xz fetched from http://ftp.gnu.org/gnu/coreutils/ on 2023-12-22. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU coreutils 9.4 August 2023 PASTE(1) Pages that refer to this page: colrm(1), column(1) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Combine every two lines of standard input Bash Command:<START>paste -d "" - -<END>

Compare "$source_file" and "$dest_file" line by line

diff "$source_file" "$dest_file"

['diff']

Output a Bash command to accomplish the following task. Task: Compare "$source_file" and "$dest_file" line by line Bash Command:<START>diff "$source_file" "$dest_file"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # diff\n\n> Compare files and directories.\n> More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.\n\n- Compare files (lists changes to turn `old_file` into `new_file`):\n\n`diff {{old_file}} {{new_file}}`\n\n- Compare files, ignoring [w]hite spaces:\n\n`diff {{-w|--ignore-all-space}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences side by side:\n\n`diff {{-y|--side-by-side}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences in [u]nified format (as used by `git diff`):\n\n`diff {{-u|--unified}} {{old_file}} {{new_file}}`\n\n- Compare directories [r]ecursively (shows names for differing files/directories as well as changes made to files):\n\n`diff {{-r|--recursive}} {{old_directory}} {{new_directory}}`\n\n- Compare directories, only showing the names of files that differ:\n\n`diff {{-r|--recursive}} {{-q|--brief}} {{old_directory}} {{new_directory}}`\n\n- Create a patch file for Git from the differences of two text files, treating nonexistent files as empty:\n\n`diff {{-a|--text}} {{-u|--unified}} {{-N|--new-file}} {{old_file}} {{new_file}} > {{diff.patch}}`\n\n- Compare files, showing output in color and try hard to find smaller set of changes:\n\n`diff {{-d|--minimal}} --color=always {{old_file}} {{new_file}}`\n Task: Compare "$source_file" and "$dest_file" line by line Bash Command:<START>diff "$source_file" "$dest_file"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: diff(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training diff(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIFF(1) User Commands DIFF(1) NAME top diff - compare files line by line SYNOPSIS top diff [OPTION]... FILES DESCRIPTION top Compare FILES line by line. Mandatory arguments to long options are mandatory for short options too. --normal output a normal diff (the default) -q, --brief report only when files differ -s, --report-identical-files report when two files are the same -c, -C NUM, --context[=NUM] output NUM (default 3) lines of copied context -u, -U NUM, --unified[=NUM] output NUM (default 3) lines of unified context -e, --ed output an ed script -n, --rcs output an RCS format diff -y, --side-by-side output in two columns -W, --width=NUM output at most NUM (default 130) print columns --left-column output only the left column of common lines --suppress-common-lines do not output common lines -p, --show-c-function show which C function each change is in -F, --show-function-line=RE show the most recent line matching RE --label LABEL use LABEL instead of file name and timestamp (can be repeated) -t, --expand-tabs expand tabs to spaces in output -T, --initial-tab make tabs line up by prepending a tab --tabsize=NUM tab stops every NUM (default 8) print columns --suppress-blank-empty suppress space or tab before empty output lines -l, --paginate pass output through 'pr' to paginate it -r, --recursive recursively compare any subdirectories found --no-dereference don't follow symbolic links -N, --new-file treat absent files as empty --unidirectional-new-file treat absent first files as empty --ignore-file-name-case ignore case when comparing file names --no-ignore-file-name-case consider case when comparing file names -x, --exclude=PAT exclude files that match PAT -X, --exclude-from=FILE exclude files that match any pattern in FILE -S, --starting-file=FILE start with FILE when comparing directories --from-file=FILE1 compare FILE1 to all operands; FILE1 can be a directory --to-file=FILE2 compare all operands to FILE2; FILE2 can be a directory -i, --ignore-case ignore case differences in file contents -E, --ignore-tab-expansion ignore changes due to tab expansion -Z, --ignore-trailing-space ignore white space at line end -b, --ignore-space-change ignore changes in the amount of white space -w, --ignore-all-space ignore all white space -B, --ignore-blank-lines ignore changes where lines are all blank -I, --ignore-matching-lines=RE ignore changes where all lines match RE -a, --text treat all files as text --strip-trailing-cr strip trailing carriage return on input -D, --ifdef=NAME output merged file with '#ifdef NAME' diffs --GTYPE-group-format=GFMT format GTYPE input groups with GFMT --line-format=LFMT format all input lines with LFMT --LTYPE-line-format=LFMT format LTYPE input lines with LFMT These format options provide fine-grained control over the output of diff, generalizing -D/--ifdef. LTYPE is 'old', 'new', or 'unchanged'. GTYPE is LTYPE or 'changed'. GFMT (only) may contain: %< lines from FILE1 %> lines from FILE2 %= lines common to FILE1 and FILE2 %[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER LETTERs are as follows for new group, lower case for old group: F first line number L last line number N number of lines = L-F+1 E F-1 M L+1 %(A=B?T:E) if A equals B then T else E LFMT (only) may contain: %L contents of line %l contents of line, excluding any trailing newline %[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number Both GFMT and LFMT may contain: %% % %c'C' the single character C %c'\OOO' the character with octal code OOO C the character C (other characters represent themselves) -d, --minimal try hard to find a smaller set of changes --horizon-lines=NUM keep NUM lines of the common prefix and suffix --speed-large-files assume large files and many scattered small changes --color[=WHEN] color output; WHEN is 'never', 'always', or 'auto'; plain --color means --color='auto' --palette=PALETTE the colors to use when --color is active; PALETTE is a colon-separated list of terminfo capabilities --help display this help and exit -v, --version output version information and exit FILES are 'FILE1 FILE2' or 'DIR1 DIR2' or 'DIR FILE' or 'FILE DIR'. If --from-file or --to-file is given, there are no restrictions on FILE(s). If a FILE is '-', read standard input. Exit status is 0 if inputs are the same, 1 if different, 2 if trouble. AUTHOR top Written by Paul Eggert, Mike Haertel, David Hayes, Richard Stallman, and Len Tower. REPORTING BUGS top Report bugs to: bug-diffutils@gnu.org GNU diffutils home page: <https://www.gnu.org/software/diffutils/> General help using GNU software: <https://www.gnu.org/gethelp/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top wdiff(1), cmp(1), diff3(1), sdiff(1), patch(1) The full documentation for diff is maintained as a Texinfo manual. If the info and diff programs are properly installed at your site, the command info diff should give you access to the complete manual. COLOPHON top This page is part of the diffutils (GNU diff utilities) project. Information about the project can be found at http://savannah.gnu.org/projects/diffutils/. If you have a bug report for this manual page, send it to bug-diffutils@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/diffutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-20.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org diffutils 3.10.207-774b December 2023 DIFF(1) Pages that refer to this page: cmp(1), diff3(1), gendiff(1), grep(1), patch(1), quilt(1), sdiff(1), suffixes(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Compare "$source_file" and "$dest_file" line by line Bash Command:<START>diff "$source_file" "$dest_file"<END>

Compare "current.log" and "previous.log" line by line and print lines containing regex pattern ">\|<"

diff current.log previous.log | grep ">\|<" #comparring users lists

['grep', 'diff']

Output a Bash command to accomplish the following task. Task: Compare "current.log" and "previous.log" line by line and print lines containing regex pattern ">\|<" Bash Command:<START>diff current.log previous.log | grep ">\|<" #comparring users lists<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # grep\n\n> Find patterns in files using regular expressions.\n> More information: <https://www.gnu.org/software/grep/manual/grep.html>.\n\n- Search for a pattern within a file:\n\n`grep "{{search_pattern}}" {{path/to/file}}`\n\n- Search for an exact string (disables regular expressions):\n\n`grep --fixed-strings "{{exact_string}}" {{path/to/file}}`\n\n- Search for a pattern in all files recursively in a directory, showing line numbers of matches, ignoring binary files:\n\n`grep --recursive --line-number --binary-files={{without-match}} "{{search_pattern}}" {{path/to/directory}}`\n\n- Use extended regular expressions (supports `?`, `+`, `{}`, `()` and `|`), in case-insensitive mode:\n\n`grep --extended-regexp --ignore-case "{{search_pattern}}" {{path/to/file}}`\n\n- Print 3 lines of context around, before, or after each match:\n\n`grep --{{context|before-context|after-context}}={{3}} "{{search_pattern}}" {{path/to/file}}`\n\n- Print file name and line number for each match with color output:\n\n`grep --with-filename --line-number --color=always "{{search_pattern}}" {{path/to/file}}`\n\n- Search for lines matching a pattern, printing only the matched text:\n\n`grep --only-matching "{{search_pattern}}" {{path/to/file}}`\n\n- Search `stdin` for lines that do not match a pattern:\n\n`cat {{path/to/file}} | grep --invert-match "{{search_pattern}}"`\n # diff\n\n> Compare files and directories.\n> More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.\n\n- Compare files (lists changes to turn `old_file` into `new_file`):\n\n`diff {{old_file}} {{new_file}}`\n\n- Compare files, ignoring [w]hite spaces:\n\n`diff {{-w|--ignore-all-space}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences side by side:\n\n`diff {{-y|--side-by-side}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences in [u]nified format (as used by `git diff`):\n\n`diff {{-u|--unified}} {{old_file}} {{new_file}}`\n\n- Compare directories [r]ecursively (shows names for differing files/directories as well as changes made to files):\n\n`diff {{-r|--recursive}} {{old_directory}} {{new_directory}}`\n\n- Compare directories, only showing the names of files that differ:\n\n`diff {{-r|--recursive}} {{-q|--brief}} {{old_directory}} {{new_directory}}`\n\n- Create a patch file for Git from the differences of two text files, treating nonexistent files as empty:\n\n`diff {{-a|--text}} {{-u|--unified}} {{-N|--new-file}} {{old_file}} {{new_file}} > {{diff.patch}}`\n\n- Compare files, showing output in color and try hard to find smaller set of changes:\n\n`diff {{-d|--minimal}} --color=always {{old_file}} {{new_file}}`\n Task: Compare "current.log" and "previous.log" line by line and print lines containing regex pattern ">\|<" Bash Command:<START>diff current.log previous.log | grep ">\|<" #comparring users lists<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: grep(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training grep(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | EXIT STATUS | ENVIRONMENT | NOTES | COPYRIGHT | BUGS | EXAMPLE | SEE ALSO | COLOPHON GREP(1) User Commands GREP(1) NAME top grep - print lines that match patterns SYNOPSIS top grep [OPTION...] PATTERNS [FILE...] grep [OPTION...] -e PATTERNS ... [FILE...] grep [OPTION...] -f PATTERN_FILE ... [FILE...] DESCRIPTION top grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern. Typically PATTERNS should be quoted when grep is used in a shell command. A FILE of - stands for standard input. If no FILE is given, recursive searches examine the working directory, and nonrecursive searches read standard input. OPTIONS top Generic Program Information --help Output a usage message and exit. -V, --version Output the version number of grep and exit. Pattern Syntax -E, --extended-regexp Interpret PATTERNS as extended regular expressions (EREs, see below). -F, --fixed-strings Interpret PATTERNS as fixed strings, not regular expressions. -G, --basic-regexp Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default. -P, --perl-regexp Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features. Matching Control -e PATTERNS, --regexp=PATTERNS Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with -. -f FILE, --file=FILE Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing. If FILE is - , read patterns from standard input. -i, --ignore-case Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. --no-ignore-case Do not ignore case distinctions in patterns and input data. This is the default. This option is useful for passing to shell scripts that already use -i, to cancel its effects because the two options override each other. -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. This option has no effect if -x is also specified. -x, --line-regexp Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $. General Output Control -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see above), count non-matching lines. --color[=WHEN], --colour[=WHEN] Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. WHEN is never, always, or auto. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If NUM is zero, grep stops right away without reading input. A NUM of -1 is treated as infinity and grep does not stop; this is the default. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. -o, --only-matching Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Output Line Prefix Control -b, --byte-offset Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself. -H, --with-filename Print the file name for each match. This is the default when there is more than one file to search. This is a GNU extension. -h, --no-filename Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search. --label=LABEL Display input actually coming from standard input as input coming from file LABEL. This can be useful for commands that transform a file's contents before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'. See also the -H option. -n, --line-number Prefix each line of output with the 1-based line number within its input file. -T, --initial-tab Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line number and byte offset (if present) to be printed in a minimum size field width. -Z, --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. Context Line Control -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. -C NUM, -NUM, --context=NUM Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given. --group-separator=SEP When -A, -B, or -C are in use, print SEP instead of -- between groups of lines. --no-group-separator When -A, -B, or -C are in use, do not print a separator between groups of lines. File and Directory Selection -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. --binary-files=TYPE If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given. By default, TYPE is binary, and grep suppresses output after null input binary data is discovered, and suppresses output lines that contain improperly encoded data. When some output is suppressed, grep follows any output with a message to standard error saying that a binary file matches. If TYPE is without-match, when grep discovers null input binary data it assumes that the rest of the file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte. Warning: The -a option might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it as commands. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option. --exclude=GLOB Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or a trailing part that starts with a non-slash character immediately after a slash (/) in the name. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last slash. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally. --exclude-from=FILE Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude). --exclude-dir=GLOB Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. --include=GLOB Search only files whose base name matches GLOB (using wildcard matching as described under --exclude). If contradictory --include and --exclude options are given, the last matching one wins. If no --include or --exclude options match, a file is included unless the first such option is --include. -r, --recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option. -R, --dereference-recursive Read all files under each directory, recursively. Follow all symbolic links, unlike -r. Other Options --line-buffered Use line buffering on output. This can cause a performance penalty. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -z, --null-data Treat input and output data as sequences of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like sort -z to process arbitrary file names. REGULAR EXPRESSIONS top A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expressions, by using various operators to combine smaller expressions. grep understands three different versions of regular expression syntax: basic (BRE), extended (ERE) and perl (PCRE). In GNU grep, basic and extended regular expressions are merely different notations for the same pattern-matching functionality. In other implementations, basic regular expressions are ordinarily less powerful than extended, though occasionally it is the other way around. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. Perl-compatible regular expressions have different functionality, and are documented in pcre2syntax(3) and pcre2pattern(3), but work only if PCRE support is enabled. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be quoted by preceding it with a backslash. The period . matches any single character. It is unspecified whether it matches an encoding error. Character Classes and Bracket Expressions A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list. If the first character of the list is the caret ^ then it matches any character not in the list; it is unspecified whether it matches an encoding error. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. Anchoring The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end of a line. The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]]. Repetition A regular expression may be followed by one of several repetition operators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {,m} The preceding item is matched at most m times. This is a GNU extension. {n,m} The preceding item is matched at least n times, but not more than m times. Concatenation Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated expressions. Alternation Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either alternate expression. Precedence Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole expression may be enclosed in parentheses to override these precedence rules and form a subexpression. Back-references and Subexpressions The back-reference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression. Basic vs Extended Regular Expressions In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). EXIT STATUS top Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and 2 if an error occurred. However, if the -q or --quiet or --silent is used and a line is selected, the exit status is 0 even if an error occurred. ENVIRONMENT top The behavior of grep is affected by the following environment variables. The locale for category LC_foo is specified by examining the three environment variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category. The C locale is used if none of these environment variables are set, if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). The shell command locale -a lists locales that are currently available. GREP_COLORS Controls how the --color option highlights output. Its value is a colon-separated list of capabilities that defaults to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne boolean capabilities omitted (i.e., false). Supported capabilities are as follows. sl= SGR substring for whole selected lines (i.e., matching lines when the -v command-line option is omitted, or non-matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to context matching lines instead. The default is empty (i.e., the terminal's default color pair). cx= SGR substring for whole context lines (i.e., non- matching lines when the -v command-line option is omitted, or matching lines when -v is specified). If however the boolean rv capability and the -v command-line option are both specified, it applies to selected non-matching lines instead. The default is empty (i.e., the terminal's default color pair). rv Boolean value that reverses (swaps) the meanings of the sl= and cx= capabilities when the -v command- line option is specified. The default is false (i.e., the capability is omitted). mt=01;31 SGR substring for matching non-empty text in any matching line (i.e., a selected line when the -v command-line option is omitted, or a context line when -v is specified). Setting this is equivalent to setting both ms= and mc= at once to the same value. The default is a bold red text foreground over the current line background. ms=01;31 SGR substring for matching non-empty text in a selected line. (This is only used when the -v command-line option is omitted.) The effect of the sl= (or cx= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. mc=01;31 SGR substring for matching non-empty text in a context line. (This is only used when the -v command-line option is specified.) The effect of the cx= (or sl= if rv) capability remains active when this kicks in. The default is a bold red text foreground over the current line background. fn=35 SGR substring for file names prefixing any content line. The default is a magenta text foreground over the terminal's default background. ln=32 SGR substring for line numbers prefixing any content line. The default is a green text foreground over the terminal's default background. bn=32 SGR substring for byte offsets prefixing any content line. The default is a green text foreground over the terminal's default background. se=36 SGR substring for separators that are inserted between selected line fields (:), between context line fields, (-), and between groups of adjacent lines when nonzero context is specified (--). The default is a cyan text foreground over the terminal's default background. ne Boolean value that prevents clearing to the end of line using Erase in Line (EL) to Right (\33[K) each time a colorized item ends. This is needed on terminals on which EL is not supported. It is otherwise useful on terminals for which the back_color_erase (bce) boolean terminfo capability does not apply, when the chosen highlight colors do not affect the background, or when EL is too slow or causes too much flicker. The default is false (i.e., the capability is omitted). Note that boolean capabilities have no =... part. They are omitted (i.e., false) by default and become true when specified. See the Select Graphic Rendition (SGR) section in the documentation of the text terminal that is used for permitted values and their meaning as character attributes. These substring values are integers in decimal representation and can be concatenated with semicolons. grep takes care of assembling the result into a complete SGR sequence (\33[...m). Common values to concatenate include 1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors. LC_ALL, LC_COLLATE, LANG These variables specify the locale for the LC_COLLATE category, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the locale for the LC_CTYPE category, which determines the type of characters, e.g., which characters are whitespace. This category also determines the character encoding, that is, whether text is encoded in UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all characters are encoded as a single byte and every byte is a valid character. LC_ALL, LC_MESSAGES, LANG These variables specify the locale for the LC_MESSAGES category, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX requires; otherwise, grep behaves more like other GNU programs. POSIX requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX requires that unrecognized options be diagnosed as illegal, but since they are not really against the law the default is to diagnose them as invalid. NOTES top This man page is maintained only fitfully; the full documentation is often more up-to-date. COPYRIGHT top Copyright 1998-2000, 2002, 2005-2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. BUGS top Reporting Bugs Email bug reports to the bug-reporting address bug- grep@gnu.org. An email archive https://lists.gnu.org/mailman/listinfo/bug-grep and a bug tracker https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep are available. Known Bugs Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Back-references are very slow, and may require exponential time. EXAMPLE top The following example outputs the location and contents of any line containing f and ending in .c, within all files in the current directory whose names contain g and end in .h. The -n option outputs line numbers, the -- argument treats expansions of *g*.h starting with - as file names not options, and the empty file /dev/null causes file names to be output even if only one file name happens to be of the form *g*.h. $ grep -n -- 'f.*\.c$' *g*.h /dev/null argmatch.h:1:/* definitions and prototypes for argmatch.c The only line that matches is line 1 of argmatch.h. Note that the regular expression syntax used in the pattern differs from the globbing syntax that the shell uses to match file names. SEE ALSO top Regular Manual Pages awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2), pcre2(3), pcre2syntax(3), pcre2pattern(3), terminfo(5), glob(7), regex(7) Full Documentation A complete manual https://www.gnu.org/software/grep/manual/ is available. If the info and grep programs are properly installed at your site, the command info grep should give you access to the complete manual. COLOPHON top This page is part of the GNU grep (regular expression file search tool) project. Information about the project can be found at https://www.gnu.org/software/grep/. If you have a bug report for this manual page, send it to bug-grep@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/grep.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU grep 3.11.21-102b-dirty 2019-12-29 GREP(1) Pages that refer to this page: look(1), pmrep(1), sed(1), regex(3), regex(7), bridge(8), ip(8), tc(8) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. diff(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training diff(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIFF(1) User Commands DIFF(1) NAME top diff - compare files line by line SYNOPSIS top diff [OPTION]... FILES DESCRIPTION top Compare FILES line by line. Mandatory arguments to long options are mandatory for short options too. --normal output a normal diff (the default) -q, --brief report only when files differ -s, --report-identical-files report when two files are the same -c, -C NUM, --context[=NUM] output NUM (default 3) lines of copied context -u, -U NUM, --unified[=NUM] output NUM (default 3) lines of unified context -e, --ed output an ed script -n, --rcs output an RCS format diff -y, --side-by-side output in two columns -W, --width=NUM output at most NUM (default 130) print columns --left-column output only the left column of common lines --suppress-common-lines do not output common lines -p, --show-c-function show which C function each change is in -F, --show-function-line=RE show the most recent line matching RE --label LABEL use LABEL instead of file name and timestamp (can be repeated) -t, --expand-tabs expand tabs to spaces in output -T, --initial-tab make tabs line up by prepending a tab --tabsize=NUM tab stops every NUM (default 8) print columns --suppress-blank-empty suppress space or tab before empty output lines -l, --paginate pass output through 'pr' to paginate it -r, --recursive recursively compare any subdirectories found --no-dereference don't follow symbolic links -N, --new-file treat absent files as empty --unidirectional-new-file treat absent first files as empty --ignore-file-name-case ignore case when comparing file names --no-ignore-file-name-case consider case when comparing file names -x, --exclude=PAT exclude files that match PAT -X, --exclude-from=FILE exclude files that match any pattern in FILE -S, --starting-file=FILE start with FILE when comparing directories --from-file=FILE1 compare FILE1 to all operands; FILE1 can be a directory --to-file=FILE2 compare all operands to FILE2; FILE2 can be a directory -i, --ignore-case ignore case differences in file contents -E, --ignore-tab-expansion ignore changes due to tab expansion -Z, --ignore-trailing-space ignore white space at line end -b, --ignore-space-change ignore changes in the amount of white space -w, --ignore-all-space ignore all white space -B, --ignore-blank-lines ignore changes where lines are all blank -I, --ignore-matching-lines=RE ignore changes where all lines match RE -a, --text treat all files as text --strip-trailing-cr strip trailing carriage return on input -D, --ifdef=NAME output merged file with '#ifdef NAME' diffs --GTYPE-group-format=GFMT format GTYPE input groups with GFMT --line-format=LFMT format all input lines with LFMT --LTYPE-line-format=LFMT format LTYPE input lines with LFMT These format options provide fine-grained control over the output of diff, generalizing -D/--ifdef. LTYPE is 'old', 'new', or 'unchanged'. GTYPE is LTYPE or 'changed'. GFMT (only) may contain: %< lines from FILE1 %> lines from FILE2 %= lines common to FILE1 and FILE2 %[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER LETTERs are as follows for new group, lower case for old group: F first line number L last line number N number of lines = L-F+1 E F-1 M L+1 %(A=B?T:E) if A equals B then T else E LFMT (only) may contain: %L contents of line %l contents of line, excluding any trailing newline %[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number Both GFMT and LFMT may contain: %% % %c'C' the single character C %c'\OOO' the character with octal code OOO C the character C (other characters represent themselves) -d, --minimal try hard to find a smaller set of changes --horizon-lines=NUM keep NUM lines of the common prefix and suffix --speed-large-files assume large files and many scattered small changes --color[=WHEN] color output; WHEN is 'never', 'always', or 'auto'; plain --color means --color='auto' --palette=PALETTE the colors to use when --color is active; PALETTE is a colon-separated list of terminfo capabilities --help display this help and exit -v, --version output version information and exit FILES are 'FILE1 FILE2' or 'DIR1 DIR2' or 'DIR FILE' or 'FILE DIR'. If --from-file or --to-file is given, there are no restrictions on FILE(s). If a FILE is '-', read standard input. Exit status is 0 if inputs are the same, 1 if different, 2 if trouble. AUTHOR top Written by Paul Eggert, Mike Haertel, David Hayes, Richard Stallman, and Len Tower. REPORTING BUGS top Report bugs to: bug-diffutils@gnu.org GNU diffutils home page: <https://www.gnu.org/software/diffutils/> General help using GNU software: <https://www.gnu.org/gethelp/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top wdiff(1), cmp(1), diff3(1), sdiff(1), patch(1) The full documentation for diff is maintained as a Texinfo manual. If the info and diff programs are properly installed at your site, the command info diff should give you access to the complete manual. COLOPHON top This page is part of the diffutils (GNU diff utilities) project. Information about the project can be found at http://savannah.gnu.org/projects/diffutils/. If you have a bug report for this manual page, send it to bug-diffutils@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/diffutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-20.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org diffutils 3.10.207-774b December 2023 DIFF(1) Pages that refer to this page: cmp(1), diff3(1), gendiff(1), grep(1), patch(1), quilt(1), sdiff(1), suffixes(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Compare "current.log" and "previous.log" line by line and print lines containing regex pattern ">\|<" Bash Command:<START>diff current.log previous.log | grep ">\|<" #comparring users lists<END>

Compare "fastcgi_params" and "fastcgi.conf" line by line, output 3 lines of unified context, and print the C function the change is in

diff -up fastcgi_params fastcgi.conf

['diff']

Output a Bash command to accomplish the following task. Task: Compare "fastcgi_params" and "fastcgi.conf" line by line, output 3 lines of unified context, and print the C function the change is in Bash Command:<START>diff -up fastcgi_params fastcgi.conf<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # diff\n\n> Compare files and directories.\n> More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.\n\n- Compare files (lists changes to turn `old_file` into `new_file`):\n\n`diff {{old_file}} {{new_file}}`\n\n- Compare files, ignoring [w]hite spaces:\n\n`diff {{-w|--ignore-all-space}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences side by side:\n\n`diff {{-y|--side-by-side}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences in [u]nified format (as used by `git diff`):\n\n`diff {{-u|--unified}} {{old_file}} {{new_file}}`\n\n- Compare directories [r]ecursively (shows names for differing files/directories as well as changes made to files):\n\n`diff {{-r|--recursive}} {{old_directory}} {{new_directory}}`\n\n- Compare directories, only showing the names of files that differ:\n\n`diff {{-r|--recursive}} {{-q|--brief}} {{old_directory}} {{new_directory}}`\n\n- Create a patch file for Git from the differences of two text files, treating nonexistent files as empty:\n\n`diff {{-a|--text}} {{-u|--unified}} {{-N|--new-file}} {{old_file}} {{new_file}} > {{diff.patch}}`\n\n- Compare files, showing output in color and try hard to find smaller set of changes:\n\n`diff {{-d|--minimal}} --color=always {{old_file}} {{new_file}}`\n Task: Compare "fastcgi_params" and "fastcgi.conf" line by line, output 3 lines of unified context, and print the C function the change is in Bash Command:<START>diff -up fastcgi_params fastcgi.conf<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: diff(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training diff(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIFF(1) User Commands DIFF(1) NAME top diff - compare files line by line SYNOPSIS top diff [OPTION]... FILES DESCRIPTION top Compare FILES line by line. Mandatory arguments to long options are mandatory for short options too. --normal output a normal diff (the default) -q, --brief report only when files differ -s, --report-identical-files report when two files are the same -c, -C NUM, --context[=NUM] output NUM (default 3) lines of copied context -u, -U NUM, --unified[=NUM] output NUM (default 3) lines of unified context -e, --ed output an ed script -n, --rcs output an RCS format diff -y, --side-by-side output in two columns -W, --width=NUM output at most NUM (default 130) print columns --left-column output only the left column of common lines --suppress-common-lines do not output common lines -p, --show-c-function show which C function each change is in -F, --show-function-line=RE show the most recent line matching RE --label LABEL use LABEL instead of file name and timestamp (can be repeated) -t, --expand-tabs expand tabs to spaces in output -T, --initial-tab make tabs line up by prepending a tab --tabsize=NUM tab stops every NUM (default 8) print columns --suppress-blank-empty suppress space or tab before empty output lines -l, --paginate pass output through 'pr' to paginate it -r, --recursive recursively compare any subdirectories found --no-dereference don't follow symbolic links -N, --new-file treat absent files as empty --unidirectional-new-file treat absent first files as empty --ignore-file-name-case ignore case when comparing file names --no-ignore-file-name-case consider case when comparing file names -x, --exclude=PAT exclude files that match PAT -X, --exclude-from=FILE exclude files that match any pattern in FILE -S, --starting-file=FILE start with FILE when comparing directories --from-file=FILE1 compare FILE1 to all operands; FILE1 can be a directory --to-file=FILE2 compare all operands to FILE2; FILE2 can be a directory -i, --ignore-case ignore case differences in file contents -E, --ignore-tab-expansion ignore changes due to tab expansion -Z, --ignore-trailing-space ignore white space at line end -b, --ignore-space-change ignore changes in the amount of white space -w, --ignore-all-space ignore all white space -B, --ignore-blank-lines ignore changes where lines are all blank -I, --ignore-matching-lines=RE ignore changes where all lines match RE -a, --text treat all files as text --strip-trailing-cr strip trailing carriage return on input -D, --ifdef=NAME output merged file with '#ifdef NAME' diffs --GTYPE-group-format=GFMT format GTYPE input groups with GFMT --line-format=LFMT format all input lines with LFMT --LTYPE-line-format=LFMT format LTYPE input lines with LFMT These format options provide fine-grained control over the output of diff, generalizing -D/--ifdef. LTYPE is 'old', 'new', or 'unchanged'. GTYPE is LTYPE or 'changed'. GFMT (only) may contain: %< lines from FILE1 %> lines from FILE2 %= lines common to FILE1 and FILE2 %[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER LETTERs are as follows for new group, lower case for old group: F first line number L last line number N number of lines = L-F+1 E F-1 M L+1 %(A=B?T:E) if A equals B then T else E LFMT (only) may contain: %L contents of line %l contents of line, excluding any trailing newline %[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number Both GFMT and LFMT may contain: %% % %c'C' the single character C %c'\OOO' the character with octal code OOO C the character C (other characters represent themselves) -d, --minimal try hard to find a smaller set of changes --horizon-lines=NUM keep NUM lines of the common prefix and suffix --speed-large-files assume large files and many scattered small changes --color[=WHEN] color output; WHEN is 'never', 'always', or 'auto'; plain --color means --color='auto' --palette=PALETTE the colors to use when --color is active; PALETTE is a colon-separated list of terminfo capabilities --help display this help and exit -v, --version output version information and exit FILES are 'FILE1 FILE2' or 'DIR1 DIR2' or 'DIR FILE' or 'FILE DIR'. If --from-file or --to-file is given, there are no restrictions on FILE(s). If a FILE is '-', read standard input. Exit status is 0 if inputs are the same, 1 if different, 2 if trouble. AUTHOR top Written by Paul Eggert, Mike Haertel, David Hayes, Richard Stallman, and Len Tower. REPORTING BUGS top Report bugs to: bug-diffutils@gnu.org GNU diffutils home page: <https://www.gnu.org/software/diffutils/> General help using GNU software: <https://www.gnu.org/gethelp/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top wdiff(1), cmp(1), diff3(1), sdiff(1), patch(1) The full documentation for diff is maintained as a Texinfo manual. If the info and diff programs are properly installed at your site, the command info diff should give you access to the complete manual. COLOPHON top This page is part of the diffutils (GNU diff utilities) project. Information about the project can be found at http://savannah.gnu.org/projects/diffutils/. If you have a bug report for this manual page, send it to bug-diffutils@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/diffutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-20.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org diffutils 3.10.207-774b December 2023 DIFF(1) Pages that refer to this page: cmp(1), diff3(1), gendiff(1), grep(1), patch(1), quilt(1), sdiff(1), suffixes(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Compare "fastcgi_params" and "fastcgi.conf" line by line, output 3 lines of unified context, and print the C function the change is in Bash Command:<START>diff -up fastcgi_params fastcgi.conf<END>

Compare "file1" and "file2" line by line with 3 lines of unified context

diff -u file1 file2

['diff']

Output a Bash command to accomplish the following task. Task: Compare "file1" and "file2" line by line with 3 lines of unified context Bash Command:<START>diff -u file1 file2<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # diff\n\n> Compare files and directories.\n> More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.\n\n- Compare files (lists changes to turn `old_file` into `new_file`):\n\n`diff {{old_file}} {{new_file}}`\n\n- Compare files, ignoring [w]hite spaces:\n\n`diff {{-w|--ignore-all-space}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences side by side:\n\n`diff {{-y|--side-by-side}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences in [u]nified format (as used by `git diff`):\n\n`diff {{-u|--unified}} {{old_file}} {{new_file}}`\n\n- Compare directories [r]ecursively (shows names for differing files/directories as well as changes made to files):\n\n`diff {{-r|--recursive}} {{old_directory}} {{new_directory}}`\n\n- Compare directories, only showing the names of files that differ:\n\n`diff {{-r|--recursive}} {{-q|--brief}} {{old_directory}} {{new_directory}}`\n\n- Create a patch file for Git from the differences of two text files, treating nonexistent files as empty:\n\n`diff {{-a|--text}} {{-u|--unified}} {{-N|--new-file}} {{old_file}} {{new_file}} > {{diff.patch}}`\n\n- Compare files, showing output in color and try hard to find smaller set of changes:\n\n`diff {{-d|--minimal}} --color=always {{old_file}} {{new_file}}`\n Task: Compare "file1" and "file2" line by line with 3 lines of unified context Bash Command:<START>diff -u file1 file2<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: diff(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training diff(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIFF(1) User Commands DIFF(1) NAME top diff - compare files line by line SYNOPSIS top diff [OPTION]... FILES DESCRIPTION top Compare FILES line by line. Mandatory arguments to long options are mandatory for short options too. --normal output a normal diff (the default) -q, --brief report only when files differ -s, --report-identical-files report when two files are the same -c, -C NUM, --context[=NUM] output NUM (default 3) lines of copied context -u, -U NUM, --unified[=NUM] output NUM (default 3) lines of unified context -e, --ed output an ed script -n, --rcs output an RCS format diff -y, --side-by-side output in two columns -W, --width=NUM output at most NUM (default 130) print columns --left-column output only the left column of common lines --suppress-common-lines do not output common lines -p, --show-c-function show which C function each change is in -F, --show-function-line=RE show the most recent line matching RE --label LABEL use LABEL instead of file name and timestamp (can be repeated) -t, --expand-tabs expand tabs to spaces in output -T, --initial-tab make tabs line up by prepending a tab --tabsize=NUM tab stops every NUM (default 8) print columns --suppress-blank-empty suppress space or tab before empty output lines -l, --paginate pass output through 'pr' to paginate it -r, --recursive recursively compare any subdirectories found --no-dereference don't follow symbolic links -N, --new-file treat absent files as empty --unidirectional-new-file treat absent first files as empty --ignore-file-name-case ignore case when comparing file names --no-ignore-file-name-case consider case when comparing file names -x, --exclude=PAT exclude files that match PAT -X, --exclude-from=FILE exclude files that match any pattern in FILE -S, --starting-file=FILE start with FILE when comparing directories --from-file=FILE1 compare FILE1 to all operands; FILE1 can be a directory --to-file=FILE2 compare all operands to FILE2; FILE2 can be a directory -i, --ignore-case ignore case differences in file contents -E, --ignore-tab-expansion ignore changes due to tab expansion -Z, --ignore-trailing-space ignore white space at line end -b, --ignore-space-change ignore changes in the amount of white space -w, --ignore-all-space ignore all white space -B, --ignore-blank-lines ignore changes where lines are all blank -I, --ignore-matching-lines=RE ignore changes where all lines match RE -a, --text treat all files as text --strip-trailing-cr strip trailing carriage return on input -D, --ifdef=NAME output merged file with '#ifdef NAME' diffs --GTYPE-group-format=GFMT format GTYPE input groups with GFMT --line-format=LFMT format all input lines with LFMT --LTYPE-line-format=LFMT format LTYPE input lines with LFMT These format options provide fine-grained control over the output of diff, generalizing -D/--ifdef. LTYPE is 'old', 'new', or 'unchanged'. GTYPE is LTYPE or 'changed'. GFMT (only) may contain: %< lines from FILE1 %> lines from FILE2 %= lines common to FILE1 and FILE2 %[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER LETTERs are as follows for new group, lower case for old group: F first line number L last line number N number of lines = L-F+1 E F-1 M L+1 %(A=B?T:E) if A equals B then T else E LFMT (only) may contain: %L contents of line %l contents of line, excluding any trailing newline %[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number Both GFMT and LFMT may contain: %% % %c'C' the single character C %c'\OOO' the character with octal code OOO C the character C (other characters represent themselves) -d, --minimal try hard to find a smaller set of changes --horizon-lines=NUM keep NUM lines of the common prefix and suffix --speed-large-files assume large files and many scattered small changes --color[=WHEN] color output; WHEN is 'never', 'always', or 'auto'; plain --color means --color='auto' --palette=PALETTE the colors to use when --color is active; PALETTE is a colon-separated list of terminfo capabilities --help display this help and exit -v, --version output version information and exit FILES are 'FILE1 FILE2' or 'DIR1 DIR2' or 'DIR FILE' or 'FILE DIR'. If --from-file or --to-file is given, there are no restrictions on FILE(s). If a FILE is '-', read standard input. Exit status is 0 if inputs are the same, 1 if different, 2 if trouble. AUTHOR top Written by Paul Eggert, Mike Haertel, David Hayes, Richard Stallman, and Len Tower. REPORTING BUGS top Report bugs to: bug-diffutils@gnu.org GNU diffutils home page: <https://www.gnu.org/software/diffutils/> General help using GNU software: <https://www.gnu.org/gethelp/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top wdiff(1), cmp(1), diff3(1), sdiff(1), patch(1) The full documentation for diff is maintained as a Texinfo manual. If the info and diff programs are properly installed at your site, the command info diff should give you access to the complete manual. COLOPHON top This page is part of the diffutils (GNU diff utilities) project. Information about the project can be found at http://savannah.gnu.org/projects/diffutils/. If you have a bug report for this manual page, send it to bug-diffutils@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/diffutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-20.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org diffutils 3.10.207-774b December 2023 DIFF(1) Pages that refer to this page: cmp(1), diff3(1), gendiff(1), grep(1), patch(1), quilt(1), sdiff(1), suffixes(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Compare "file1" and "file2" line by line with 3 lines of unified context Bash Command:<START>diff -u file1 file2<END>

Compare *.csv files in the current directory tree with their analogs stored in /some/other/path/

find . -name "*.csv" -exec diff {} /some/other/path/{} ";" -print

['find', 'diff']

Output a Bash command to accomplish the following task. Task: Compare *.csv files in the current directory tree with their analogs stored in /some/other/path/ Bash Command:<START>find . -name "*.csv" -exec diff {} /some/other/path/{} ";" -print<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # diff\n\n> Compare files and directories.\n> More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.\n\n- Compare files (lists changes to turn `old_file` into `new_file`):\n\n`diff {{old_file}} {{new_file}}`\n\n- Compare files, ignoring [w]hite spaces:\n\n`diff {{-w|--ignore-all-space}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences side by side:\n\n`diff {{-y|--side-by-side}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences in [u]nified format (as used by `git diff`):\n\n`diff {{-u|--unified}} {{old_file}} {{new_file}}`\n\n- Compare directories [r]ecursively (shows names for differing files/directories as well as changes made to files):\n\n`diff {{-r|--recursive}} {{old_directory}} {{new_directory}}`\n\n- Compare directories, only showing the names of files that differ:\n\n`diff {{-r|--recursive}} {{-q|--brief}} {{old_directory}} {{new_directory}}`\n\n- Create a patch file for Git from the differences of two text files, treating nonexistent files as empty:\n\n`diff {{-a|--text}} {{-u|--unified}} {{-N|--new-file}} {{old_file}} {{new_file}} > {{diff.patch}}`\n\n- Compare files, showing output in color and try hard to find smaller set of changes:\n\n`diff {{-d|--minimal}} --color=always {{old_file}} {{new_file}}`\n Task: Compare *.csv files in the current directory tree with their analogs stored in /some/other/path/ Bash Command:<START>find . -name "*.csv" -exec diff {} /some/other/path/{} ";" -print<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. diff(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training diff(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIFF(1) User Commands DIFF(1) NAME top diff - compare files line by line SYNOPSIS top diff [OPTION]... FILES DESCRIPTION top Compare FILES line by line. Mandatory arguments to long options are mandatory for short options too. --normal output a normal diff (the default) -q, --brief report only when files differ -s, --report-identical-files report when two files are the same -c, -C NUM, --context[=NUM] output NUM (default 3) lines of copied context -u, -U NUM, --unified[=NUM] output NUM (default 3) lines of unified context -e, --ed output an ed script -n, --rcs output an RCS format diff -y, --side-by-side output in two columns -W, --width=NUM output at most NUM (default 130) print columns --left-column output only the left column of common lines --suppress-common-lines do not output common lines -p, --show-c-function show which C function each change is in -F, --show-function-line=RE show the most recent line matching RE --label LABEL use LABEL instead of file name and timestamp (can be repeated) -t, --expand-tabs expand tabs to spaces in output -T, --initial-tab make tabs line up by prepending a tab --tabsize=NUM tab stops every NUM (default 8) print columns --suppress-blank-empty suppress space or tab before empty output lines -l, --paginate pass output through 'pr' to paginate it -r, --recursive recursively compare any subdirectories found --no-dereference don't follow symbolic links -N, --new-file treat absent files as empty --unidirectional-new-file treat absent first files as empty --ignore-file-name-case ignore case when comparing file names --no-ignore-file-name-case consider case when comparing file names -x, --exclude=PAT exclude files that match PAT -X, --exclude-from=FILE exclude files that match any pattern in FILE -S, --starting-file=FILE start with FILE when comparing directories --from-file=FILE1 compare FILE1 to all operands; FILE1 can be a directory --to-file=FILE2 compare all operands to FILE2; FILE2 can be a directory -i, --ignore-case ignore case differences in file contents -E, --ignore-tab-expansion ignore changes due to tab expansion -Z, --ignore-trailing-space ignore white space at line end -b, --ignore-space-change ignore changes in the amount of white space -w, --ignore-all-space ignore all white space -B, --ignore-blank-lines ignore changes where lines are all blank -I, --ignore-matching-lines=RE ignore changes where all lines match RE -a, --text treat all files as text --strip-trailing-cr strip trailing carriage return on input -D, --ifdef=NAME output merged file with '#ifdef NAME' diffs --GTYPE-group-format=GFMT format GTYPE input groups with GFMT --line-format=LFMT format all input lines with LFMT --LTYPE-line-format=LFMT format LTYPE input lines with LFMT These format options provide fine-grained control over the output of diff, generalizing -D/--ifdef. LTYPE is 'old', 'new', or 'unchanged'. GTYPE is LTYPE or 'changed'. GFMT (only) may contain: %< lines from FILE1 %> lines from FILE2 %= lines common to FILE1 and FILE2 %[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER LETTERs are as follows for new group, lower case for old group: F first line number L last line number N number of lines = L-F+1 E F-1 M L+1 %(A=B?T:E) if A equals B then T else E LFMT (only) may contain: %L contents of line %l contents of line, excluding any trailing newline %[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number Both GFMT and LFMT may contain: %% % %c'C' the single character C %c'\OOO' the character with octal code OOO C the character C (other characters represent themselves) -d, --minimal try hard to find a smaller set of changes --horizon-lines=NUM keep NUM lines of the common prefix and suffix --speed-large-files assume large files and many scattered small changes --color[=WHEN] color output; WHEN is 'never', 'always', or 'auto'; plain --color means --color='auto' --palette=PALETTE the colors to use when --color is active; PALETTE is a colon-separated list of terminfo capabilities --help display this help and exit -v, --version output version information and exit FILES are 'FILE1 FILE2' or 'DIR1 DIR2' or 'DIR FILE' or 'FILE DIR'. If --from-file or --to-file is given, there are no restrictions on FILE(s). If a FILE is '-', read standard input. Exit status is 0 if inputs are the same, 1 if different, 2 if trouble. AUTHOR top Written by Paul Eggert, Mike Haertel, David Hayes, Richard Stallman, and Len Tower. REPORTING BUGS top Report bugs to: bug-diffutils@gnu.org GNU diffutils home page: <https://www.gnu.org/software/diffutils/> General help using GNU software: <https://www.gnu.org/gethelp/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top wdiff(1), cmp(1), diff3(1), sdiff(1), patch(1) The full documentation for diff is maintained as a Texinfo manual. If the info and diff programs are properly installed at your site, the command info diff should give you access to the complete manual. COLOPHON top This page is part of the diffutils (GNU diff utilities) project. Information about the project can be found at http://savannah.gnu.org/projects/diffutils/. If you have a bug report for this manual page, send it to bug-diffutils@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/diffutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-20.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org diffutils 3.10.207-774b December 2023 DIFF(1) Pages that refer to this page: cmp(1), diff3(1), gendiff(1), grep(1), patch(1), quilt(1), sdiff(1), suffixes(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Compare *.csv files in the current directory tree with their analogs stored in /some/other/path/ Bash Command:<START>find . -name "*.csv" -exec diff {} /some/other/path/{} ";" -print<END>

Compare *.csv files in the current directory tree with their analogs stored in /some/other/path/ prompting before running `diff'

find . -okdir diff {} /some/other/path/{} ";"

['find', 'diff']

Output a Bash command to accomplish the following task. Task: Compare *.csv files in the current directory tree with their analogs stored in /some/other/path/ prompting before running `diff' Bash Command:<START>find . -okdir diff {} /some/other/path/{} ";"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # diff\n\n> Compare files and directories.\n> More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.\n\n- Compare files (lists changes to turn `old_file` into `new_file`):\n\n`diff {{old_file}} {{new_file}}`\n\n- Compare files, ignoring [w]hite spaces:\n\n`diff {{-w|--ignore-all-space}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences side by side:\n\n`diff {{-y|--side-by-side}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences in [u]nified format (as used by `git diff`):\n\n`diff {{-u|--unified}} {{old_file}} {{new_file}}`\n\n- Compare directories [r]ecursively (shows names for differing files/directories as well as changes made to files):\n\n`diff {{-r|--recursive}} {{old_directory}} {{new_directory}}`\n\n- Compare directories, only showing the names of files that differ:\n\n`diff {{-r|--recursive}} {{-q|--brief}} {{old_directory}} {{new_directory}}`\n\n- Create a patch file for Git from the differences of two text files, treating nonexistent files as empty:\n\n`diff {{-a|--text}} {{-u|--unified}} {{-N|--new-file}} {{old_file}} {{new_file}} > {{diff.patch}}`\n\n- Compare files, showing output in color and try hard to find smaller set of changes:\n\n`diff {{-d|--minimal}} --color=always {{old_file}} {{new_file}}`\n Task: Compare *.csv files in the current directory tree with their analogs stored in /some/other/path/ prompting before running `diff' Bash Command:<START>find . -okdir diff {} /some/other/path/{} ";"<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. diff(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training diff(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIFF(1) User Commands DIFF(1) NAME top diff - compare files line by line SYNOPSIS top diff [OPTION]... FILES DESCRIPTION top Compare FILES line by line. Mandatory arguments to long options are mandatory for short options too. --normal output a normal diff (the default) -q, --brief report only when files differ -s, --report-identical-files report when two files are the same -c, -C NUM, --context[=NUM] output NUM (default 3) lines of copied context -u, -U NUM, --unified[=NUM] output NUM (default 3) lines of unified context -e, --ed output an ed script -n, --rcs output an RCS format diff -y, --side-by-side output in two columns -W, --width=NUM output at most NUM (default 130) print columns --left-column output only the left column of common lines --suppress-common-lines do not output common lines -p, --show-c-function show which C function each change is in -F, --show-function-line=RE show the most recent line matching RE --label LABEL use LABEL instead of file name and timestamp (can be repeated) -t, --expand-tabs expand tabs to spaces in output -T, --initial-tab make tabs line up by prepending a tab --tabsize=NUM tab stops every NUM (default 8) print columns --suppress-blank-empty suppress space or tab before empty output lines -l, --paginate pass output through 'pr' to paginate it -r, --recursive recursively compare any subdirectories found --no-dereference don't follow symbolic links -N, --new-file treat absent files as empty --unidirectional-new-file treat absent first files as empty --ignore-file-name-case ignore case when comparing file names --no-ignore-file-name-case consider case when comparing file names -x, --exclude=PAT exclude files that match PAT -X, --exclude-from=FILE exclude files that match any pattern in FILE -S, --starting-file=FILE start with FILE when comparing directories --from-file=FILE1 compare FILE1 to all operands; FILE1 can be a directory --to-file=FILE2 compare all operands to FILE2; FILE2 can be a directory -i, --ignore-case ignore case differences in file contents -E, --ignore-tab-expansion ignore changes due to tab expansion -Z, --ignore-trailing-space ignore white space at line end -b, --ignore-space-change ignore changes in the amount of white space -w, --ignore-all-space ignore all white space -B, --ignore-blank-lines ignore changes where lines are all blank -I, --ignore-matching-lines=RE ignore changes where all lines match RE -a, --text treat all files as text --strip-trailing-cr strip trailing carriage return on input -D, --ifdef=NAME output merged file with '#ifdef NAME' diffs --GTYPE-group-format=GFMT format GTYPE input groups with GFMT --line-format=LFMT format all input lines with LFMT --LTYPE-line-format=LFMT format LTYPE input lines with LFMT These format options provide fine-grained control over the output of diff, generalizing -D/--ifdef. LTYPE is 'old', 'new', or 'unchanged'. GTYPE is LTYPE or 'changed'. GFMT (only) may contain: %< lines from FILE1 %> lines from FILE2 %= lines common to FILE1 and FILE2 %[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER LETTERs are as follows for new group, lower case for old group: F first line number L last line number N number of lines = L-F+1 E F-1 M L+1 %(A=B?T:E) if A equals B then T else E LFMT (only) may contain: %L contents of line %l contents of line, excluding any trailing newline %[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number Both GFMT and LFMT may contain: %% % %c'C' the single character C %c'\OOO' the character with octal code OOO C the character C (other characters represent themselves) -d, --minimal try hard to find a smaller set of changes --horizon-lines=NUM keep NUM lines of the common prefix and suffix --speed-large-files assume large files and many scattered small changes --color[=WHEN] color output; WHEN is 'never', 'always', or 'auto'; plain --color means --color='auto' --palette=PALETTE the colors to use when --color is active; PALETTE is a colon-separated list of terminfo capabilities --help display this help and exit -v, --version output version information and exit FILES are 'FILE1 FILE2' or 'DIR1 DIR2' or 'DIR FILE' or 'FILE DIR'. If --from-file or --to-file is given, there are no restrictions on FILE(s). If a FILE is '-', read standard input. Exit status is 0 if inputs are the same, 1 if different, 2 if trouble. AUTHOR top Written by Paul Eggert, Mike Haertel, David Hayes, Richard Stallman, and Len Tower. REPORTING BUGS top Report bugs to: bug-diffutils@gnu.org GNU diffutils home page: <https://www.gnu.org/software/diffutils/> General help using GNU software: <https://www.gnu.org/gethelp/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top wdiff(1), cmp(1), diff3(1), sdiff(1), patch(1) The full documentation for diff is maintained as a Texinfo manual. If the info and diff programs are properly installed at your site, the command info diff should give you access to the complete manual. COLOPHON top This page is part of the diffutils (GNU diff utilities) project. Information about the project can be found at http://savannah.gnu.org/projects/diffutils/. If you have a bug report for this manual page, send it to bug-diffutils@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/diffutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-20.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org diffutils 3.10.207-774b December 2023 DIFF(1) Pages that refer to this page: cmp(1), diff3(1), gendiff(1), grep(1), patch(1), quilt(1), sdiff(1), suffixes(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Compare *.csv files in the current directory tree with their analogs stored in /some/other/path/ prompting before running `diff' Bash Command:<START>find . -okdir diff {} /some/other/path/{} ";"<END>

Compare column 3 with column 2 of the next line in "file" and format output as a table

awk 'NR==1 { print; next } { print $0, ($1 == a && $2 == b) ? "equal" : "not_equal"; a = $1; b = $3 }' file | column -t

['awk', 'file', 'column']

Output a Bash command to accomplish the following task. Task: Compare column 3 with column 2 of the next line in "file" and format output as a table Bash Command:<START>awk 'NR==1 { print; next } { print $0, ($1 == a && $2 == b) ? "equal" : "not_equal"; a = $1; b = $3 }' file | column -t<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # awk\n\n> A versatile programming language for working on files.\n> More information: <https://github.com/onetrueawk/awk>.\n\n- Print the fifth column (a.k.a. field) in a space-separated file:\n\n`awk '{print $5}' {{path/to/file}}`\n\n- Print the second column of the lines containing "foo" in a space-separated file:\n\n`awk '/{{foo}}/ {print $2}' {{path/to/file}}`\n\n- Print the last column of each line in a file, using a comma (instead of space) as a field separator:\n\n`awk -F ',' '{print $NF}' {{path/to/file}}`\n\n- Sum the values in the first column of a file and print the total:\n\n`awk '{s+=$1} END {print s}' {{path/to/file}}`\n\n- Print every third line starting from the first line:\n\n`awk 'NR%3==1' {{path/to/file}}`\n\n- Print different values based on conditions:\n\n`awk '{if ($1 == "foo") print "Exact match foo"; else if ($1 ~ "bar") print "Partial match bar"; else print "Baz"}' {{path/to/file}}`\n\n- Print all lines where the 10th column value equals the specified value:\n\n`awk '($10 == {{value}})'`\n\n- Print all the lines which the 10th column value is between a min and a max:\n\n`awk '($10 >= {{min_value}} && $10 <= {{max_value}})'`\n # file\n\n> Determine file type.\n> More information: <https://manned.org/file>.\n\n- Give a description of the type of the specified file. Works fine for files with no file extension:\n\n`file {{path/to/file}}`\n\n- Look inside a zipped file and determine the file type(s) inside:\n\n`file -z {{foo.zip}}`\n\n- Allow file to work with special or device files:\n\n`file -s {{path/to/file}}`\n\n- Don't stop at first file type match; keep going until the end of the file:\n\n`file -k {{path/to/file}}`\n\n- Determine the MIME encoding type of a file:\n\n`file -i {{path/to/file}}`\n # column\n\n> Format `stdin` or a file into multiple columns.\n> Columns are filled before rows; the default separator is a whitespace.\n> More information: <https://manned.org/column>.\n\n- Format the output of a command for a 30 characters wide display:\n\n`printf "header1 header2\nbar foo\n" | column --output-width {{30}}`\n\n- Split columns automatically and auto-align them in a tabular format:\n\n`printf "header1 header2\nbar foo\n" | column --table`\n\n- Specify the column delimiter character for the `--table` option (e.g. "," for CSV) (defaults to whitespace):\n\n`printf "header1,header2\nbar,foo\n" | column --table --separator {{,}}`\n\n- Fill rows before filling columns:\n\n`printf "header1\nbar\nfoobar\n" | column --output-width {{30}} --fillrows`\n Task: Compare column 3 with column 2 of the next line in "file" and format output as a table Bash Command:<START>awk 'NR==1 { print; next } { print $0, ($1 == a && $2 == b) ? "equal" : "not_equal"; a = $1; b = $3 }' file | column -t<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: awk(1p) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training awk(1p) Linux manual page PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT AWK(1P) POSIX Programmer's Manual AWK(1P) PROLOG top This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. NAME top awk pattern scanning and processing language SYNOPSIS top awk [-F sepstring] [-v assignment]... program [argument...] awk [-F sepstring] -f progfile [-f progfile]... [-v assignment]... [argument...] DESCRIPTION top The awk utility shall execute programs written in the awk programming language, which is specialized for textual data manipulation. An awk program is a sequence of patterns and corresponding actions. When input is read that matches a pattern, the action associated with that pattern is carried out. Input shall be interpreted as a sequence of records. By default, a record is a line, less its terminating <newline>, but this can be changed by using the RS built-in variable. Each record of input shall be matched in turn against each pattern in the program. For each pattern matched, the associated action shall be executed. The awk utility shall interpret each input record as a sequence of fields where, by default, a field is a string of non-<blank> non-<newline> characters. This default <blank> and <newline> field delimiter can be changed by using the FS built-in variable or the -F sepstring option. The awk utility shall denote the first field in a record $1, the second $2, and so on. The symbol $0 shall refer to the entire record; setting any other field causes the re-evaluation of $0. Assigning to $0 shall reset the values of all other fields and the NF built-in variable. OPTIONS top The awk utility shall conform to the Base Definitions volume of POSIX.12017, Section 12.2, Utility Syntax Guidelines. The following options shall be supported: -F sepstring Define the input field separator. This option shall be equivalent to: -v FS=sepstring except that if -F sepstring and -v FS=sepstring are both used, it is unspecified whether the FS assignment resulting from -F sepstring is processed in command line order or is processed after the last -v FS=sepstring. See the description of the FS built-in variable, and how it is used, in the EXTENDED DESCRIPTION section. -f progfile Specify the pathname of the file progfile containing an awk program. A pathname of '-' shall denote the standard input. If multiple instances of this option are specified, the concatenation of the files specified as progfile in the order specified shall be the awk program. The awk program can alternatively be specified in the command line as a single argument. -v assignment The application shall ensure that the assignment argument is in the same form as an assignment operand. The specified variable assignment shall occur prior to executing the awk program, including the actions associated with BEGIN patterns (if any). Multiple occurrences of this option can be specified. OPERANDS top The following operands shall be supported: program If no -f option is specified, the first operand to awk shall be the text of the awk program. The application shall supply the program operand as a single argument to awk. If the text does not end in a <newline>, awk shall interpret the text as if it did. argument Either of the following two types of argument can be intermixed: file A pathname of a file that contains the input to be read, which is matched against the set of patterns in the program. If no file operands are specified, or if a file operand is '-', the standard input shall be used. assignment An operand that begins with an <underscore> or alphabetic character from the portable character set (see the table in the Base Definitions volume of POSIX.12017, Section 6.1, Portable Character Set), followed by a sequence of underscores, digits, and alphabetics from the portable character set, followed by the '=' character, shall specify a variable assignment rather than a pathname. The characters before the '=' represent the name of an awk variable; if that name is an awk reserved word (see Grammar) the behavior is undefined. The characters following the <equals-sign> shall be interpreted as if they appeared in the awk program preceded and followed by a double-quote ('"') character, as a STRING token (see Grammar), except that if the last character is an unescaped <backslash>, it shall be interpreted as a literal <backslash> rather than as the first character of the sequence "\"". The variable shall be assigned the value of that STRING token and, if appropriate, shall be considered a numeric string (see Expressions in awk), the variable shall also be assigned its numeric value. Each such variable assignment shall occur just prior to the processing of the following file, if any. Thus, an assignment before the first file argument shall be executed after the BEGIN actions (if any), while an assignment after the last file argument shall occur before the END actions (if any). If there are no file arguments, assignments shall be executed before processing the standard input. STDIN top The standard input shall be used only if no file operands are specified, or if a file operand is '-', or if a progfile option- argument is '-'; see the INPUT FILES section. If the awk program contains no actions and no patterns, but is otherwise a valid awk program, standard input and any file operands shall not be read and awk shall exit with a return status of zero. INPUT FILES top Input files to the awk program from any of the following sources shall be text files: * Any file operands or their equivalents, achieved by modifying the awk variables ARGV and ARGC * Standard input in the absence of any file operands * Arguments to the getline function Whether the variable RS is set to a value other than a <newline> or not, for these files, implementations shall support records terminated with the specified separator up to {LINE_MAX} bytes and may support longer records. If -f progfile is specified, the application shall ensure that the files named by each of the progfile option-arguments are text files and their concatenation, in the same order as they appear in the arguments, is an awk program. ENVIRONMENT VARIABLES top The following environment variables shall affect the execution of awk: LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.12017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE Determine the locale for the behavior of ranges, equivalence classes, and multi-character collating elements within regular expressions and in comparisons of string values. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments and input files), the behavior of character classes within regular expressions, the identification of characters as letters, and the mapping of uppercase and lowercase characters for the toupper and tolower functions. LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error. LC_NUMERIC Determine the radix character used when interpreting numeric input, performing conversions between numeric and string values, and formatting numeric output. Regardless of locale, the <period> character (the decimal-point character of the POSIX locale) is the decimal-point character recognized in processing awk programs (including assignments in command line arguments). NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES. PATH Determine the search path when looking for commands executed by system(expr), or input and output pipes; see the Base Definitions volume of POSIX.12017, Chapter 8, Environment Variables. In addition, all environment variables shall be visible via the awk variable ENVIRON. ASYNCHRONOUS EVENTS top Default. STDOUT top The nature of the output files depends on the awk program. STDERR top The standard error shall be used only for diagnostic messages. OUTPUT FILES top The nature of the output files depends on the awk program. EXTENDED DESCRIPTION top Overall Program Structure An awk program is composed of pairs of the form: pattern { action } Either the pattern or the action (including the enclosing brace characters) can be omitted. A missing pattern shall match any record of input, and a missing action shall be equivalent to: { print } Execution of the awk program shall start by first executing the actions associated with all BEGIN patterns in the order they occur in the program. Then each file operand (or standard input if no files were specified) shall be processed in turn by reading data from the file until a record separator is seen (<newline> by default). Before the first reference to a field in the record is evaluated, the record shall be split into fields, according to the rules in Regular Expressions, using the value of FS that was current at the time the record was read. Each pattern in the program then shall be evaluated in the order of occurrence, and the action associated with each pattern that matches the current record executed. The action for a matching pattern shall be executed before evaluating subsequent patterns. Finally, the actions associated with all END patterns shall be executed in the order they occur in the program. Expressions in awk Expressions describe computations used in patterns and actions. In the following table, valid expression operations are given in groups from highest precedence first to lowest precedence last, with equal-precedence operators grouped between horizontal lines. In expression evaluation, where the grammar is formally ambiguous, higher precedence operators shall be evaluated before lower precedence operators. In this table expr, expr1, expr2, and expr3 represent any expression, while lvalue represents any entity that can be assigned to (that is, on the left side of an assignment operator). The precise syntax of expressions is given in Grammar. Table 4-1: Expressions in Decreasing Precedence in awk Syntax Name Type of Result Associativity ( expr ) Grouping Type of expr N/A $expr Field reference String N/A lvalue ++ Post-increment Numeric N/A lvalue -- Post-decrement Numeric N/A ++ lvalue Pre-increment Numeric N/A -- lvalue Pre-decrement Numeric N/A expr ^ expr Exponentiation Numeric Right ! expr Logical not Numeric N/A + expr Unary plus Numeric N/A - expr Unary minus Numeric N/A expr * expr Multiplication Numeric Left expr / expr Division Numeric Left expr % expr Modulus Numeric Left expr + expr Addition Numeric Left expr - expr Subtraction Numeric Left expr expr String concatenation String Left expr < expr Less than Numeric None expr <= expr Less than or equal to Numeric None expr != expr Not equal to Numeric None expr == expr Equal to Numeric None expr > expr Greater than Numeric None expr >= expr Greater than or equal to Numeric None expr ~ expr ERE match Numeric None expr !~ expr ERE non-match Numeric None expr in array Array membership Numeric Left ( index ) in array Multi-dimension array Numeric Left membership expr && expr Logical AND Numeric Left expr || expr Logical OR Numeric Left expr1 ? expr2 : expr3Conditional expression Type of selectedRight expr2 or expr3 lvalue ^= expr Exponentiation assignmentNumeric Right lvalue %= expr Modulus assignment Numeric Right lvalue *= expr Multiplication assignmentNumeric Right lvalue /= expr Division assignment Numeric Right lvalue += expr Addition assignment Numeric Right lvalue -= expr Subtraction assignment Numeric Right lvalue = expr Assignment Type of expr Right Each expression shall have either a string value, a numeric value, or both. Except as stated for specific contexts, the value of an expression shall be implicitly converted to the type needed for the context in which it is used. A string value shall be converted to a numeric value either by the equivalent of the following calls to functions defined by the ISO C standard: setlocale(LC_NUMERIC, ""); numeric_value = atof(string_value); or by converting the initial portion of the string to type double representation as follows: The input string is decomposed into two parts: an initial, possibly empty, sequence of white-space characters (as specified by isspace()) and a subject sequence interpreted as a floating-point constant. The expected form of the subject sequence is an optional '+' or '-' sign, then a non-empty sequence of digits optionally containing a <period>, then an optional exponent part. An exponent part consists of 'e' or 'E', followed by an optional sign, followed by one or more decimal digits. The sequence starting with the first digit or the <period> (whichever occurs first) is interpreted as a floating constant of the C language, and if neither an exponent part nor a <period> appears, a <period> is assumed to follow the last digit in the string. If the subject sequence begins with a <hyphen-minus>, the value resulting from the conversion is negated. A numeric value that is exactly equal to the value of an integer (see Section 1.1.2, Concepts Derived from the ISO C Standard) shall be converted to a string by the equivalent of a call to the sprintf function (see String Functions) with the string "%d" as the fmt argument and the numeric value being converted as the first and only expr argument. Any other numeric value shall be converted to a string by the equivalent of a call to the sprintf function with the value of the variable CONVFMT as the fmt argument and the numeric value being converted as the first and only expr argument. The result of the conversion is unspecified if the value of CONVFMT is not a floating-point format specification. This volume of POSIX.12017 specifies no explicit conversions between numbers and strings. An application can force an expression to be treated as a number by adding zero to it, or can force it to be treated as a string by concatenating the null string ("") to it. A string value shall be considered a numeric string if it comes from one of the following: 1. Field variables 2. Input from the getline() function 3. FILENAME 4. ARGV array elements 5. ENVIRON array elements 6. Array elements created by the split() function 7. A command line variable assignment 8. Variable assignment from another numeric string variable and an implementation-dependent condition corresponding to either case (a) or (b) below is met. a. After the equivalent of the following calls to functions defined by the ISO C standard, string_value_end would differ from string_value, and any characters before the terminating null character in string_value_end would be <blank> characters: char *string_value_end; setlocale(LC_NUMERIC, ""); numeric_value = strtod (string_value, &string_value_end); b. After all the following conversions have been applied, the resulting string would lexically be recognized as a NUMBER token as described by the lexical conventions in Grammar: -- All leading and trailing <blank> characters are discarded. -- If the first non-<blank> is '+' or '-', it is discarded. -- Each occurrence of the decimal point character from the current locale is changed to a <period>. In case (a) the numeric value of the numeric string shall be the value that would be returned by the strtod() call. In case (b) if the first non-<blank> is '-', the numeric value of the numeric string shall be the negation of the numeric value of the recognized NUMBER token; otherwise, the numeric value of the numeric string shall be the numeric value of the recognized NUMBER token. Whether or not a string is a numeric string shall be relevant only in contexts where that term is used in this section. When an expression is used in a Boolean context, if it has a numeric value, a value of zero shall be treated as false and any other value shall be treated as true. Otherwise, a string value of the null string shall be treated as false and any other value shall be treated as true. A Boolean context shall be one of the following: * The first subexpression of a conditional expression * An expression operated on by logical NOT, logical AND, or logical OR * The second expression of a for statement * The expression of an if statement * The expression of the while clause in either a while or do...while statement * An expression used as a pattern (as in Overall Program Structure) All arithmetic shall follow the semantics of floating-point arithmetic as specified by the ISO C standard (see Section 1.1.2, Concepts Derived from the ISO C Standard). The value of the expression: expr1 ^ expr2 shall be equivalent to the value returned by the ISO C standard function call: pow(expr1, expr2) The expression: lvalue ^= expr shall be equivalent to the ISO C standard expression: lvalue = pow(lvalue, expr) except that lvalue shall be evaluated only once. The value of the expression: expr1 % expr2 shall be equivalent to the value returned by the ISO C standard function call: fmod(expr1, expr2) The expression: lvalue %= expr shall be equivalent to the ISO C standard expression: lvalue = fmod(lvalue, expr) except that lvalue shall be evaluated only once. Variables and fields shall be set by the assignment statement: lvalue = expression and the type of expression shall determine the resulting variable type. The assignment includes the arithmetic assignments ("+=", "-=", "*=", "/=", "%=", "^=", "++", "--") all of which shall produce a numeric result. The left-hand side of an assignment and the target of increment and decrement operators can be one of a variable, an array with index, or a field selector. The awk language supplies arrays that are used for storing numbers or strings. Arrays need not be declared. They shall initially be empty, and their sizes shall change dynamically. The subscripts, or element identifiers, are strings, providing a type of associative array capability. An array name followed by a subscript within square brackets can be used as an lvalue and thus as an expression, as described in the grammar; see Grammar. Unsubscripted array names can be used in only the following contexts: * A parameter in a function definition or function call * The NAME token following any use of the keyword in as specified in the grammar (see Grammar); if the name used in this context is not an array name, the behavior is undefined A valid array index shall consist of one or more <comma>-separated expressions, similar to the way in which multi- dimensional arrays are indexed in some programming languages. Because awk arrays are really one-dimensional, such a <comma>-separated list shall be converted to a single string by concatenating the string values of the separate expressions, each separated from the other by the value of the SUBSEP variable. Thus, the following two index operations shall be equivalent: var[expr1, expr2, ... exprn] var[expr1 SUBSEP expr2 SUBSEP ... SUBSEP exprn] The application shall ensure that a multi-dimensioned index used with the in operator is parenthesized. The in operator, which tests for the existence of a particular array element, shall not cause that element to exist. Any other reference to a nonexistent array element shall automatically create it. Comparisons (with the '<', "<=", "!=", "==", '>', and ">=" operators) shall be made numerically if both operands are numeric, if one is numeric and the other has a string value that is a numeric string, or if one is numeric and the other has the uninitialized value. Otherwise, operands shall be converted to strings as required and a string comparison shall be made as follows: * For the "!=" and "==" operators, the strings should be compared to check if they are identical but may be compared using the locale-specific collation sequence to check if they collate equally. * For the other operators, the strings shall be compared using the locale-specific collation sequence. The value of the comparison expression shall be 1 if the relation is true, or 0 if the relation is false. Variables and Special Variables Variables can be used in an awk program by referencing them. With the exception of function parameters (see User-Defined Functions), they are not explicitly declared. Function parameter names shall be local to the function; all other variable names shall be global. The same name shall not be used as both a function parameter name and as the name of a function or a special awk variable. The same name shall not be used both as a variable name with global scope and as the name of a function. The same name shall not be used within the same scope both as a scalar variable and as an array. Uninitialized variables, including scalar variables, array elements, and field variables, shall have an uninitialized value. An uninitialized value shall have both a numeric value of zero and a string value of the empty string. Evaluation of variables with an uninitialized value, to either string or numeric, shall be determined by the context in which they are used. Field variables shall be designated by a '$' followed by a number or numerical expression. The effect of the field number expression evaluating to anything other than a non-negative integer is unspecified; uninitialized variables or string values need not be converted to numeric values in this context. New field variables can be created by assigning a value to them. References to nonexistent fields (that is, fields after $NF), shall evaluate to the uninitialized value. Such references shall not create new fields. However, assigning to a nonexistent field (for example, $(NF+2)=5) shall increase the value of NF; create any intervening fields with the uninitialized value; and cause the value of $0 to be recomputed, with the fields being separated by the value of OFS. Each field variable shall have a string value or an uninitialized value when created. Field variables shall have the uninitialized value when created from $0 using FS and the variable does not contain any characters. If appropriate, the field variable shall be considered a numeric string (see Expressions in awk). Implementations shall support the following other special variables that are set by awk: ARGC The number of elements in the ARGV array. ARGV An array of command line arguments, excluding options and the program argument, numbered from zero to ARGC-1. The arguments in ARGV can be modified or added to; ARGC can be altered. As each input file ends, awk shall treat the next non-null element of ARGV, up to the current value of ARGC-1, inclusive, as the name of the next input file. Thus, setting an element of ARGV to null means that it shall not be treated as an input file. The name '-' indicates the standard input. If an argument matches the format of an assignment operand, this argument shall be treated as an assignment rather than a file argument. CONVFMT The printf format for converting numbers to strings (except for output statements, where OFMT is used); "%.6g" by default. ENVIRON An array representing the value of the environment, as described in the exec functions defined in the System Interfaces volume of POSIX.12017. The indices of the array shall be strings consisting of the names of the environment variables, and the value of each array element shall be a string consisting of the value of that variable. If appropriate, the environment variable shall be considered a numeric string (see Expressions in awk); the array element shall also have its numeric value. In all cases where the behavior of awk is affected by environment variables (including the environment of any commands that awk executes via the system function or via pipeline redirections with the print statement, the printf statement, or the getline function), the environment used shall be the environment at the time awk began executing; it is implementation-defined whether any modification of ENVIRON affects this environment. FILENAME A pathname of the current input file. Inside a BEGIN action the value is undefined. Inside an END action the value shall be the name of the last input file processed. FNR The ordinal number of the current record in the current file. Inside a BEGIN action the value shall be zero. Inside an END action the value shall be the number of the last record processed in the last file processed. FS Input field separator regular expression; a <space> by default. NF The number of fields in the current record. Inside a BEGIN action, the use of NF is undefined unless a getline function without a var argument is executed previously. Inside an END action, NF shall retain the value it had for the last record read, unless a subsequent, redirected, getline function without a var argument is performed prior to entering the END action. NR The ordinal number of the current record from the start of input. Inside a BEGIN action the value shall be zero. Inside an END action the value shall be the number of the last record processed. OFMT The printf format for converting numbers to strings in output statements (see Output Statements); "%.6g" by default. The result of the conversion is unspecified if the value of OFMT is not a floating-point format specification. OFS The print statement output field separator; <space> by default. ORS The print statement output record separator; a <newline> by default. RLENGTH The length of the string matched by the match function. RS The first character of the string value of RS shall be the input record separator; a <newline> by default. If RS contains more than one character, the results are unspecified. If RS is null, then records are separated by sequences consisting of a <newline> plus one or more blank lines, leading or trailing blank lines shall not result in empty records at the beginning or end of the input, and a <newline> shall always be a field separator, no matter what the value of FS is. RSTART The starting position of the string matched by the match function, numbering from 1. This shall always be equivalent to the return value of the match function. SUBSEP The subscript separator string for multi-dimensional arrays; the default value is implementation-defined. Regular Expressions The awk utility shall make use of the extended regular expression notation (see the Base Definitions volume of POSIX.12017, Section 9.4, Extended Regular Expressions) except that it shall allow the use of C-language conventions for escaping special characters within the EREs, as specified in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v') and the following table; these escape sequences shall be recognized both inside and outside bracket expressions. Note that records need not be separated by <newline> characters and string constants can contain <newline> characters, so even the "\n" sequence is valid in awk EREs. Using a <slash> character within an ERE requires the escaping shown in the following table. Table 4-2: Escape Sequences in awk Escape Sequence Description Meaning \" <backslash> <quotation-mark> <quotation-mark> character \/ <backslash> <slash> <slash> character \ddd A <backslash> character followed The character whose encoding is by the longest sequence of one, represented by the one, two, or two, or three octal-digit three-digit octal integer. Multi- characters (01234567). If all of byte characters require multiple, the digits are 0 (that is, concatenated escape sequences of representation of the NUL this type, including the leading character), the behavior is <backslash> for each byte. undefined. \c A <backslash> character followed Undefined by any character not described in this table or in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v'). A regular expression can be matched against a specific field or string by using one of the two regular expression matching operators, '~' and "!~". These operators shall interpret their right-hand operand as a regular expression and their left-hand operand as a string. If the regular expression matches the string, the '~' expression shall evaluate to a value of 1, and the "!~" expression shall evaluate to a value of 0. (The regular expression matching operation is as defined by the term matched in the Base Definitions volume of POSIX.12017, Section 9.1, Regular Expression Definitions, where a match occurs on any part of the string unless the regular expression is limited with the <circumflex> or <dollar-sign> special characters.) If the regular expression does not match the string, the '~' expression shall evaluate to a value of 0, and the "!~" expression shall evaluate to a value of 1. If the right-hand operand is any expression other than the lexical token ERE, the string value of the expression shall be interpreted as an extended regular expression, including the escape conventions described above. Note that these same escape conventions shall also be applied in determining the value of a string literal (the lexical token STRING), and thus shall be applied a second time when a string literal is used in this context. When an ERE token appears as an expression in any context other than as the right-hand of the '~' or "!~" operator or as one of the built-in function arguments described below, the value of the resulting expression shall be the equivalent of: $0 ~ /ere/ The ere argument to the gsub, match, sub functions, and the fs argument to the split function (see String Functions) shall be interpreted as extended regular expressions. These can be either ERE tokens or arbitrary expressions, and shall be interpreted in the same manner as the right-hand side of the '~' or "!~" operator. An extended regular expression can be used to separate fields by assigning a string containing the expression to the built-in variable FS, either directly or as a consequence of using the -F sepstring option. The default value of the FS variable shall be a single <space>. The following describes FS behavior: 1. If FS is a null string, the behavior is unspecified. 2. If FS is a single character: a. If FS is <space>, skip leading and trailing <blank> and <newline> characters; fields shall be delimited by sets of one or more <blank> or <newline> characters. b. Otherwise, if FS is any other character c, fields shall be delimited by each single occurrence of c. 3. Otherwise, the string value of FS shall be considered to be an extended regular expression. Each occurrence of a sequence matching the extended regular expression shall delimit fields. Except for the '~' and "!~" operators, and in the gsub, match, split, and sub built-in functions, ERE matching shall be based on input records; that is, record separator characters (the first character of the value of the variable RS, <newline> by default) cannot be embedded in the expression, and no expression shall match the record separator character. If the record separator is not <newline>, <newline> characters embedded in the expression can be matched. For the '~' and "!~" operators, and in those four built-in functions, ERE matching shall be based on text strings; that is, any character (including <newline> and the record separator) can be embedded in the pattern, and an appropriate pattern shall match any character. However, in all awk ERE matching, the use of one or more NUL characters in the pattern, input record, or text string produces undefined results. Patterns A pattern is any valid expression, a range specified by two expressions separated by a comma, or one of the two special patterns BEGIN or END. Special Patterns The awk utility shall recognize two special patterns, BEGIN and END. Each BEGIN pattern shall be matched once and its associated action executed before the first record of input is readexcept possibly by use of the getline function (see Input/Output and General Functions) in a prior BEGIN actionand before command line assignment is done. Each END pattern shall be matched once and its associated action executed after the last record of input has been read. These two patterns shall have associated actions. BEGIN and END shall not combine with other patterns. Multiple BEGIN and END patterns shall be allowed. The actions associated with the BEGIN patterns shall be executed in the order specified in the program, as are the END actions. An END pattern can precede a BEGIN pattern in a program. If an awk program consists of only actions with the pattern BEGIN, and the BEGIN action contains no getline function, awk shall exit without reading its input when the last statement in the last BEGIN action is executed. If an awk program consists of only actions with the pattern END or only actions with the patterns BEGIN and END, the input shall be read before the statements in the END actions are executed. Expression Patterns An expression pattern shall be evaluated as if it were an expression in a Boolean context. If the result is true, the pattern shall be considered to match, and the associated action (if any) shall be executed. If the result is false, the action shall not be executed. Pattern Ranges A pattern range consists of two expressions separated by a comma; in this case, the action shall be performed for all records between a match of the first expression and the following match of the second expression, inclusive. At this point, the pattern range can be repeated starting at input records subsequent to the end of the matched range. Actions An action is a sequence of statements as shown in the grammar in Grammar. Any single statement can be replaced by a statement list enclosed in curly braces. The application shall ensure that statements in a statement list are separated by <newline> or <semicolon> characters. Statements in a statement list shall be executed sequentially in the order that they appear. The expression acting as the conditional in an if statement shall be evaluated and if it is non-zero or non-null, the following statement shall be executed; otherwise, if else is present, the statement following the else shall be executed. The if, while, do...while, for, break, and continue statements are based on the ISO C standard (see Section 1.1.2, Concepts Derived from the ISO C Standard), except that the Boolean expressions shall be treated as described in Expressions in awk, and except in the case of: for (variable in array) which shall iterate, assigning each index of array to variable in an unspecified order. The results of adding new elements to array within such a for loop are undefined. If a break or continue statement occurs outside of a loop, the behavior is undefined. The delete statement shall remove an individual array element. Thus, the following code deletes an entire array: for (index in array) delete array[index] The next statement shall cause all further processing of the current input record to be abandoned. The behavior is undefined if a next statement appears or is invoked in a BEGIN or END action. The exit statement shall invoke all END actions in the order in which they occur in the program source and then terminate the program without reading further input. An exit statement inside an END action shall terminate the program without further execution of END actions. If an expression is specified in an exit statement, its numeric value shall be the exit status of awk, unless subsequent errors are encountered or a subsequent exit statement with an expression is executed. Output Statements Both print and printf statements shall write to standard output by default. The output shall be written to the location specified by output_redirection if one is supplied, as follows: > expression >> expression | expression In all cases, the expression shall be evaluated to produce a string that is used as a pathname into which to write (for '>' or ">>") or as a command to be executed (for '|'). Using the first two forms, if the file of that name is not currently open, it shall be opened, creating it if necessary and using the first form, truncating the file. The output then shall be appended to the file. As long as the file remains open, subsequent calls in which expression evaluates to the same string value shall simply append output to the file. The file remains open until the close function (see Input/Output and General Functions) is called with an expression that evaluates to the same string value. The third form shall write output onto a stream piped to the input of a command. The stream shall be created if no stream is currently open with the value of expression as its command name. The stream created shall be equivalent to one created by a call to the popen() function defined in the System Interfaces volume of POSIX.12017 with the value of expression as the command argument and a value of w as the mode argument. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value shall write output to the existing stream. The stream shall remain open until the close function (see Input/Output and General Functions) is called with an expression that evaluates to the same string value. At that time, the stream shall be closed as if by a call to the pclose() function defined in the System Interfaces volume of POSIX.12017. As described in detail by the grammar in Grammar, these output statements shall take a <comma>-separated list of expressions referred to in the grammar by the non-terminal symbols expr_list, print_expr_list, or print_expr_list_opt. This list is referred to here as the expression list, and each member is referred to as an expression argument. The print statement shall write the value of each expression argument onto the indicated output stream separated by the current output field separator (see variable OFS above), and terminated by the output record separator (see variable ORS above). All expression arguments shall be taken as strings, being converted if necessary; this conversion shall be as described in Expressions in awk, with the exception that the printf format in OFMT shall be used instead of the value in CONVFMT. An empty expression list shall stand for the whole input record ($0). The printf statement shall produce output based on a notation similar to the File Format Notation used to describe file formats in this volume of POSIX.12017 (see the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation). Output shall be produced as specified with the first expression argument as the string format and subsequent expression arguments as the strings arg1 to argn, inclusive, with the following exceptions: 1. The format shall be an actual character string rather than a graphical representation. Therefore, it cannot contain empty character positions. The <space> in the format string, in any context other than a flag of a conversion specification, shall be treated as an ordinary character that is copied to the output. 2. If the character set contains a '' character and that character appears in the format string, it shall be treated as an ordinary character that is copied to the output. 3. The escape sequences beginning with a <backslash> character shall be treated as sequences of ordinary characters that are copied to the output. Note that these same sequences shall be interpreted lexically by awk when they appear in literal strings, but they shall not be treated specially by the printf statement. 4. A field width or precision can be specified as the '*' character instead of a digit string. In this case the next argument from the expression list shall be fetched and its numeric value taken as the field width or precision. 5. The implementation shall not precede or follow output from the d or u conversion specifier characters with <blank> characters not specified by the format string. 6. The implementation shall not precede output from the o conversion specifier character with leading zeros not specified by the format string. 7. For the c conversion specifier character: if the argument has a numeric value, the character whose encoding is that value shall be output. If the value is zero or is not the encoding of any character in the character set, the behavior is undefined. If the argument does not have a numeric value, the first character of the string value shall be output; if the string does not contain any characters, the behavior is undefined. 8. For each conversion specification that consumes an argument, the next expression argument shall be evaluated. With the exception of the c conversion specifier character, the value shall be converted (according to the rules specified in Expressions in awk) to the appropriate type for the conversion specification. 9. If there are insufficient expression arguments to satisfy all the conversion specifications in the format string, the behavior is undefined. 10. If any character sequence in the format string begins with a '%' character, but does not form a valid conversion specification, the behavior is unspecified. Both print and printf can output at least {LINE_MAX} bytes. Functions The awk language has a variety of built-in functions: arithmetic, string, input/output, and general. Arithmetic Functions The arithmetic functions, except for int, shall be based on the ISO C standard (see Section 1.1.2, Concepts Derived from the ISO C Standard). The behavior is undefined in cases where the ISO C standard specifies that an error be returned or that the behavior is undefined. Although the grammar (see Grammar) permits built-in functions to appear with no arguments or parentheses, unless the argument or parentheses are indicated as optional in the following list (by displaying them within the "[]" brackets), such use is undefined. atan2(y,x) Return arctangent of y/x in radians in the range [-,]. cos(x) Return cosine of x, where x is in radians. sin(x) Return sine of x, where x is in radians. exp(x) Return the exponential function of x. log(x) Return the natural logarithm of x. sqrt(x) Return the square root of x. int(x) Return the argument truncated to an integer. Truncation shall be toward 0 when x>0. rand() Return a random number n, such that 0n<1. srand([expr]) Set the seed value for rand to expr or use the time of day if expr is omitted. The previous seed value shall be returned. String Functions The string functions in the following list shall be supported. Although the grammar (see Grammar) permits built-in functions to appear with no arguments or parentheses, unless the argument or parentheses are indicated as optional in the following list (by displaying them within the "[]" brackets), such use is undefined. gsub(ere, repl[, in]) Behave like sub (see below), except that it shall replace all occurrences of the regular expression (like the ed utility global substitute) in $0 or in the in argument, when specified. index(s, t) Return the position, in characters, numbering from 1, in string s where string t first occurs, or zero if it does not occur at all. length[([s])] Return the length, in characters, of its argument taken as a string, or of the whole record, $0, if there is no argument. match(s, ere) Return the position, in characters, numbering from 1, in string s where the extended regular expression ere occurs, or zero if it does not occur at all. RSTART shall be set to the starting position (which is the same as the returned value), zero if no match is found; RLENGTH shall be set to the length of the matched string, -1 if no match is found. split(s, a[, fs ]) Split the string s into array elements a[1], a[2], ..., a[n], and return n. All elements of the array shall be deleted before the split is performed. The separation shall be done with the ERE fs or with the field separator FS if fs is not given. Each array element shall have a string value when created and, if appropriate, the array element shall be considered a numeric string (see Expressions in awk). The effect of a null string as the value of fs is unspecified. sprintf(fmt, expr, expr, ...) Format the expressions according to the printf format given by fmt and return the resulting string. sub(ere, repl[, in ]) Substitute the string repl in place of the first instance of the extended regular expression ERE in string in and return the number of substitutions. An <ampersand> ('&') appearing in the string repl shall be replaced by the string from in that matches the ERE. An <ampersand> preceded with a <backslash> shall be interpreted as the literal <ampersand> character. An occurrence of two consecutive <backslash> characters shall be interpreted as just a single literal <backslash> character. Any other occurrence of a <backslash> (for example, preceding any other character) shall be treated as a literal <backslash> character. Note that if repl is a string literal (the lexical token STRING; see Grammar), the handling of the <ampersand> character occurs after any lexical processing, including any lexical <backslash>-escape sequence processing. If in is specified and it is not an lvalue (see Expressions in awk), the behavior is undefined. If in is omitted, awk shall use the current record ($0) in its place. substr(s, m[, n ]) Return the at most n-character substring of s that begins at position m, numbering from 1. If n is omitted, or if n specifies more characters than are left in the string, the length of the substring shall be limited by the length of the string s. tolower(s) Return a string based on the string s. Each character in s that is an uppercase letter specified to have a tolower mapping by the LC_CTYPE category of the current locale shall be replaced in the returned string by the lowercase letter specified by the mapping. Other characters in s shall be unchanged in the returned string. toupper(s) Return a string based on the string s. Each character in s that is a lowercase letter specified to have a toupper mapping by the LC_CTYPE category of the current locale is replaced in the returned string by the uppercase letter specified by the mapping. Other characters in s are unchanged in the returned string. All of the preceding functions that take ERE as a parameter expect a pattern or a string valued expression that is a regular expression as defined in Regular Expressions. Input/Output and General Functions The input/output and general functions are: close(expression) Close the file or pipe opened by a print or printf statement or a call to getline with the same string- valued expression. The limit on the number of open expression arguments is implementation-defined. If the close was successful, the function shall return zero; otherwise, it shall return non-zero. expression | getline [var] Read a record of input from a stream piped from the output of a command. The stream shall be created if no stream is currently open with the value of expression as its command name. The stream created shall be equivalent to one created by a call to the popen() function with the value of expression as the command argument and a value of r as the mode argument. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value shall read subsequent records from the stream. The stream shall remain open until the close function is called with an expression that evaluates to the same string value. At that time, the stream shall be closed as if by a call to the pclose() function. If var is omitted, $0 and NF shall be set; otherwise, var shall be set and, if appropriate, it shall be considered a numeric string (see Expressions in awk). The getline operator can form ambiguous constructs when there are unparenthesized operators (including concatenate) to the left of the '|' (to the beginning of the expression containing getline). In the context of the '$' operator, '|' shall behave as if it had a lower precedence than '$'. The result of evaluating other operators is unspecified, and conforming applications shall parenthesize properly all such usages. getline Set $0 to the next input record from the current input file. This form of getline shall set the NF, NR, and FNR variables. getline var Set variable var to the next input record from the current input file and, if appropriate, var shall be considered a numeric string (see Expressions in awk). This form of getline shall set the FNR and NR variables. getline [var] < expression Read the next record of input from a named file. The expression shall be evaluated to produce a string that is used as a pathname. If the file of that name is not currently open, it shall be opened. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value shall read subsequent records from the file. The file shall remain open until the close function is called with an expression that evaluates to the same string value. If var is omitted, $0 and NF shall be set; otherwise, var shall be set and, if appropriate, it shall be considered a numeric string (see Expressions in awk). The getline operator can form ambiguous constructs when there are unparenthesized binary operators (including concatenate) to the right of the '<' (up to the end of the expression containing the getline). The result of evaluating such a construct is unspecified, and conforming applications shall parenthesize properly all such usages. system(expression) Execute the command given by expression in a manner equivalent to the system() function defined in the System Interfaces volume of POSIX.12017 and return the exit status of the command. All forms of getline shall return 1 for successful input, zero for end-of-file, and -1 for an error. Where strings are used as the name of a file or pipeline, the application shall ensure that the strings are textually identical. The terminology ``same string value'' implies that ``equivalent strings'', even those that differ only by <space> characters, represent different files. User-Defined Functions The awk language also provides user-defined functions. Such functions can be defined as: function name([parameter, ...]) { statements } A function can be referred to anywhere in an awk program; in particular, its use can precede its definition. The scope of a function is global. Function parameters, if present, can be either scalars or arrays; the behavior is undefined if an array name is passed as a parameter that the function uses as a scalar, or if a scalar expression is passed as a parameter that the function uses as an array. Function parameters shall be passed by value if scalar and by reference if array name. The number of parameters in the function definition need not match the number of parameters in the function call. Excess formal parameters can be used as local variables. If fewer arguments are supplied in a function call than are in the function definition, the extra parameters that are used in the function body as scalars shall evaluate to the uninitialized value until they are otherwise initialized, and the extra parameters that are used in the function body as arrays shall be treated as uninitialized arrays where each element evaluates to the uninitialized value until otherwise initialized. When invoking a function, no white space can be placed between the function name and the opening parenthesis. Function calls can be nested and recursive calls can be made upon functions. Upon return from any nested or recursive function call, the values of all of the calling function's parameters shall be unchanged, except for array parameters passed by reference. The return statement can be used to return a value. If a return statement appears outside of a function definition, the behavior is undefined. In the function definition, <newline> characters shall be optional before the opening brace and after the closing brace. Function definitions can appear anywhere in the program where a pattern-action pair is allowed. Grammar The grammar in this section and the lexical conventions in the following section shall together describe the syntax for awk programs. The general conventions for this style of grammar are described in Section 1.3, Grammar Conventions. A valid program can be represented as the non-terminal symbol program in the grammar. This formal syntax shall take precedence over the preceding text syntax description. %token NAME NUMBER STRING ERE %token FUNC_NAME /* Name followed by '(' without white space. */ /* Keywords */ %token Begin End /* 'BEGIN' 'END' */ %token Break Continue Delete Do Else /* 'break' 'continue' 'delete' 'do' 'else' */ %token Exit For Function If In /* 'exit' 'for' 'function' 'if' 'in' */ %token Next Print Printf Return While /* 'next' 'print' 'printf' 'return' 'while' */ /* Reserved function names */ %token BUILTIN_FUNC_NAME /* One token for the following: * atan2 cos sin exp log sqrt int rand srand * gsub index length match split sprintf sub * substr tolower toupper close system */ %token GETLINE /* Syntactically different from other built-ins. */ /* Two-character tokens. */ %token ADD_ASSIGN SUB_ASSIGN MUL_ASSIGN DIV_ASSIGN MOD_ASSIGN POW_ASSIGN /* '+=' '-=' '*=' '/=' '%=' '^=' */ %token OR AND NO_MATCH EQ LE GE NE INCR DECR APPEND /* '||' '&&' '!~' '==' '<=' '>=' '!=' '++' '--' '>>' */ /* One-character tokens. */ %token '{' '}' '(' ')' '[' ']' ',' ';' NEWLINE %token '+' '-' '*' '%' '^' '!' '>' '<' '|' '?' ':' '~' '$' '=' %start program %% program : item_list | item_list item ; item_list : /* empty */ | item_list item terminator ; item : action | pattern action | normal_pattern | Function NAME '(' param_list_opt ')' newline_opt action | Function FUNC_NAME '(' param_list_opt ')' newline_opt action ; param_list_opt : /* empty */ | param_list ; param_list : NAME | param_list ',' NAME ; pattern : normal_pattern | special_pattern ; normal_pattern : expr | expr ',' newline_opt expr ; special_pattern : Begin | End ; action : '{' newline_opt '}' | '{' newline_opt terminated_statement_list '}' | '{' newline_opt unterminated_statement_list '}' ; terminator : terminator NEWLINE | ';' | NEWLINE ; terminated_statement_list : terminated_statement | terminated_statement_list terminated_statement ; unterminated_statement_list : unterminated_statement | terminated_statement_list unterminated_statement ; terminated_statement : action newline_opt | If '(' expr ')' newline_opt terminated_statement | If '(' expr ')' newline_opt terminated_statement Else newline_opt terminated_statement | While '(' expr ')' newline_opt terminated_statement | For '(' simple_statement_opt ';' expr_opt ';' simple_statement_opt ')' newline_opt terminated_statement | For '(' NAME In NAME ')' newline_opt terminated_statement | ';' newline_opt | terminatable_statement NEWLINE newline_opt | terminatable_statement ';' newline_opt ; unterminated_statement : terminatable_statement | If '(' expr ')' newline_opt unterminated_statement | If '(' expr ')' newline_opt terminated_statement Else newline_opt unterminated_statement | While '(' expr ')' newline_opt unterminated_statement | For '(' simple_statement_opt ';' expr_opt ';' simple_statement_opt ')' newline_opt unterminated_statement | For '(' NAME In NAME ')' newline_opt unterminated_statement ; terminatable_statement : simple_statement | Break | Continue | Next | Exit expr_opt | Return expr_opt | Do newline_opt terminated_statement While '(' expr ')' ; simple_statement_opt : /* empty */ | simple_statement ; simple_statement : Delete NAME '[' expr_list ']' | expr | print_statement ; print_statement : simple_print_statement | simple_print_statement output_redirection ; simple_print_statement : Print print_expr_list_opt | Print '(' multiple_expr_list ')' | Printf print_expr_list | Printf '(' multiple_expr_list ')' ; output_redirection : '>' expr | APPEND expr | '|' expr ; expr_list_opt : /* empty */ | expr_list ; expr_list : expr | multiple_expr_list ; multiple_expr_list : expr ',' newline_opt expr | multiple_expr_list ',' newline_opt expr ; expr_opt : /* empty */ | expr ; expr : unary_expr | non_unary_expr ; unary_expr : '+' expr | '-' expr | unary_expr '^' expr | unary_expr '*' expr | unary_expr '/' expr | unary_expr '%' expr | unary_expr '+' expr | unary_expr '-' expr | unary_expr non_unary_expr | unary_expr '<' expr | unary_expr LE expr | unary_expr NE expr | unary_expr EQ expr | unary_expr '>' expr | unary_expr GE expr | unary_expr '~' expr | unary_expr NO_MATCH expr | unary_expr In NAME | unary_expr AND newline_opt expr | unary_expr OR newline_opt expr | unary_expr '?' expr ':' expr | unary_input_function ; non_unary_expr : '(' expr ')' | '!' expr | non_unary_expr '^' expr | non_unary_expr '*' expr | non_unary_expr '/' expr | non_unary_expr '%' expr | non_unary_expr '+' expr | non_unary_expr '-' expr | non_unary_expr non_unary_expr | non_unary_expr '<' expr | non_unary_expr LE expr | non_unary_expr NE expr | non_unary_expr EQ expr | non_unary_expr '>' expr | non_unary_expr GE expr | non_unary_expr '~' expr | non_unary_expr NO_MATCH expr | non_unary_expr In NAME | '(' multiple_expr_list ')' In NAME | non_unary_expr AND newline_opt expr | non_unary_expr OR newline_opt expr | non_unary_expr '?' expr ':' expr | NUMBER | STRING | lvalue | ERE | lvalue INCR | lvalue DECR | INCR lvalue | DECR lvalue | lvalue POW_ASSIGN expr | lvalue MOD_ASSIGN expr | lvalue MUL_ASSIGN expr | lvalue DIV_ASSIGN expr | lvalue ADD_ASSIGN expr | lvalue SUB_ASSIGN expr | lvalue '=' expr | FUNC_NAME '(' expr_list_opt ')' /* no white space allowed before '(' */ | BUILTIN_FUNC_NAME '(' expr_list_opt ')' | BUILTIN_FUNC_NAME | non_unary_input_function ; print_expr_list_opt : /* empty */ | print_expr_list ; print_expr_list : print_expr | print_expr_list ',' newline_opt print_expr ; print_expr : unary_print_expr | non_unary_print_expr ; unary_print_expr : '+' print_expr | '-' print_expr | unary_print_expr '^' print_expr | unary_print_expr '*' print_expr | unary_print_expr '/' print_expr | unary_print_expr '%' print_expr | unary_print_expr '+' print_expr | unary_print_expr '-' print_expr | unary_print_expr non_unary_print_expr | unary_print_expr '~' print_expr | unary_print_expr NO_MATCH print_expr | unary_print_expr In NAME | unary_print_expr AND newline_opt print_expr | unary_print_expr OR newline_opt print_expr | unary_print_expr '?' print_expr ':' print_expr ; non_unary_print_expr : '(' expr ')' | '!' print_expr | non_unary_print_expr '^' print_expr | non_unary_print_expr '*' print_expr | non_unary_print_expr '/' print_expr | non_unary_print_expr '%' print_expr | non_unary_print_expr '+' print_expr | non_unary_print_expr '-' print_expr | non_unary_print_expr non_unary_print_expr | non_unary_print_expr '~' print_expr | non_unary_print_expr NO_MATCH print_expr | non_unary_print_expr In NAME | '(' multiple_expr_list ')' In NAME | non_unary_print_expr AND newline_opt print_expr | non_unary_print_expr OR newline_opt print_expr | non_unary_print_expr '?' print_expr ':' print_expr | NUMBER | STRING | lvalue | ERE | lvalue INCR | lvalue DECR | INCR lvalue | DECR lvalue | lvalue POW_ASSIGN print_expr | lvalue MOD_ASSIGN print_expr | lvalue MUL_ASSIGN print_expr | lvalue DIV_ASSIGN print_expr | lvalue ADD_ASSIGN print_expr | lvalue SUB_ASSIGN print_expr | lvalue '=' print_expr | FUNC_NAME '(' expr_list_opt ')' /* no white space allowed before '(' */ | BUILTIN_FUNC_NAME '(' expr_list_opt ')' | BUILTIN_FUNC_NAME ; lvalue : NAME | NAME '[' expr_list ']' | '$' expr ; non_unary_input_function : simple_get | simple_get '<' expr | non_unary_expr '|' simple_get ; unary_input_function : unary_expr '|' simple_get ; simple_get : GETLINE | GETLINE lvalue ; newline_opt : /* empty */ | newline_opt NEWLINE ; This grammar has several ambiguities that shall be resolved as follows: * Operator precedence and associativity shall be as described in Table 4-1, Expressions in Decreasing Precedence in awk. * In case of ambiguity, an else shall be associated with the most immediately preceding if that would satisfy the grammar. * In some contexts, a <slash> ('/') that is used to surround an ERE could also be the division operator. This shall be resolved in such a way that wherever the division operator could appear, a <slash> is assumed to be the division operator. (There is no unary division operator.) Each expression in an awk program shall conform to the precedence and associativity rules, even when this is not needed to resolve an ambiguity. For example, because '$' has higher precedence than '++', the string "$x++--" is not a valid awk expression, even though it is unambiguously parsed by the grammar as "$(x++)--". One convention that might not be obvious from the formal grammar is where <newline> characters are acceptable. There are several obvious placements such as terminating a statement, and a <backslash> can be used to escape <newline> characters between any lexical tokens. In addition, <newline> characters without <backslash> characters can follow a comma, an open brace, logical AND operator ("&&"), logical OR operator ("||"), the do keyword, the else keyword, and the closing parenthesis of an if, for, or while statement. For example: { print $1, $2 } Lexical Conventions The lexical conventions for awk programs, with respect to the preceding grammar, shall be as follows: 1. Except as noted, awk shall recognize the longest possible token or delimiter beginning at a given point. 2. A comment shall consist of any characters beginning with the <number-sign> character and terminated by, but excluding the next occurrence of, a <newline>. Comments shall have no effect, except to delimit lexical tokens. 3. The <newline> shall be recognized as the token NEWLINE. 4. A <backslash> character immediately followed by a <newline> shall have no effect. 5. The token STRING shall represent a string constant. A string constant shall begin with the character '"'. Within a string constant, a <backslash> character shall be considered to begin an escape sequence as specified in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation ('\\', '\a', '\b', '\f', '\n', '\r', '\t', '\v'). In addition, the escape sequences in Table 4-2, Escape Sequences in awk shall be recognized. A <newline> shall not occur within a string constant. A string constant shall be terminated by the first unescaped occurrence of the character '"' after the one that begins the string constant. The value of the string shall be the sequence of all unescaped characters and values of escape sequences between, but not including, the two delimiting '"' characters. 6. The token ERE represents an extended regular expression constant. An ERE constant shall begin with the <slash> character. Within an ERE constant, a <backslash> character shall be considered to begin an escape sequence as specified in the table in the Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation. In addition, the escape sequences in Table 4-2, Escape Sequences in awk shall be recognized. The application shall ensure that a <newline> does not occur within an ERE constant. An ERE constant shall be terminated by the first unescaped occurrence of the <slash> character after the one that begins the ERE constant. The extended regular expression represented by the ERE constant shall be the sequence of all unescaped characters and values of escape sequences between, but not including, the two delimiting <slash> characters. 7. A <blank> shall have no effect, except to delimit lexical tokens or within STRING or ERE tokens. 8. The token NUMBER shall represent a numeric constant. Its form and numeric value shall either be equivalent to the decimal- floating-constant token as specified by the ISO C standard, or it shall be a sequence of decimal digits and shall be evaluated as an integer constant in decimal. In addition, implementations may accept numeric constants with the form and numeric value equivalent to the hexadecimal-constant and hexadecimal-floating-constant tokens as specified by the ISO C standard. If the value is too large or too small to be representable (see Section 1.1.2, Concepts Derived from the ISO C Standard), the behavior is undefined. 9. A sequence of underscores, digits, and alphabetics from the portable character set (see the Base Definitions volume of POSIX.12017, Section 6.1, Portable Character Set), beginning with an <underscore> or alphabetic character, shall be considered a word. 10. The following words are keywords that shall be recognized as individual tokens; the name of the token is the same as the keyword: BEGIN delete END function in printf break do exit getline next return continue else for if print while 11. The following words are names of built-in functions and shall be recognized as the token BUILTIN_FUNC_NAME: atan2 gsub log split sub toupper close index match sprintf substr cos int rand sqrt system exp length sin srand tolower The above-listed keywords and names of built-in functions are considered reserved words. 12. The token NAME shall consist of a word that is not a keyword or a name of a built-in function and is not followed immediately (without any delimiters) by the '(' character. 13. The token FUNC_NAME shall consist of a word that is not a keyword or a name of a built-in function, followed immediately (without any delimiters) by the '(' character. The '(' character shall not be included as part of the token. 14. The following two-character sequences shall be recognized as the named tokens: Token Name Sequence Token Name Sequence ADD_ASSIGN += NO_MATCH !~ SUB_ASSIGN -= EQ == MUL_ASSIGN *= LE <= DIV_ASSIGN /= GE >= MOD_ASSIGN %= NE != POW_ASSIGN ^= INCR ++ OR || DECR -- AND && APPEND >> 15. The following single characters shall be recognized as tokens whose names are the character: <newline> { } ( ) [ ] , ; + - * % ^ ! > < | ? : ~ $ = There is a lexical ambiguity between the token ERE and the tokens '/' and DIV_ASSIGN. When an input sequence begins with a <slash> character in any syntactic context where the token '/' or DIV_ASSIGN could appear as the next token in a valid program, the longer of those two tokens that can be recognized shall be recognized. In any other syntactic context where the token ERE could appear as the next token in a valid program, the token ERE shall be recognized. EXIT STATUS top The following exit values shall be returned: 0 All input files were processed successfully. >0 An error occurred. The exit status can be altered within the program by using an exit expression. CONSEQUENCES OF ERRORS top If any file operand is specified and the named file cannot be accessed, awk shall write a diagnostic message to standard error and terminate without any further action. If the program specified by either the program operand or a progfile operand is not a valid awk program (as specified in the EXTENDED DESCRIPTION section), the behavior is undefined. The following sections are informative. APPLICATION USAGE top The index, length, match, and substr functions should not be confused with similar functions in the ISO C standard; the awk versions deal with characters, while the ISO C standard deals with bytes. Because the concatenation operation is represented by adjacent expressions rather than an explicit operator, it is often necessary to use parentheses to enforce the proper evaluation precedence. When using awk to process pathnames, it is recommended that LC_ALL, or at least LC_CTYPE and LC_COLLATE, are set to POSIX or C in the environment, since pathnames can contain byte sequences that do not form valid characters in some locales, in which case the utility's behavior would be undefined. In the POSIX locale each byte is a valid single-byte character, and therefore this problem is avoided. On implementations where the "==" operator checks if strings collate equally, applications needing to check whether strings are identical can use: length(a) == length(b) && index(a,b) == 1 On implementations where the "==" operator checks if strings are identical, applications needing to check whether strings collate equally can use: a <= b && a >= b EXAMPLES top The awk program specified in the command line is most easily specified within single-quotes (for example, 'program') for applications using sh, because awk programs commonly contain characters that are special to the shell, including double- quotes. In the cases where an awk program contains single-quote characters, it is usually easiest to specify most of the program as strings within single-quotes concatenated by the shell with quoted single-quote characters. For example: awk '/'\''/ { print "quote:", $0 }' prints all lines from the standard input containing a single- quote character, prefixed with quote:. The following are examples of simple awk programs: 1. Write to the standard output all input lines for which field 3 is greater than 5: $3 > 5 2. Write every tenth line: (NR % 10) == 0 3. Write any line with a substring matching the regular expression: /(G|D)(2[0-9][[:alpha:]]*)/ 4. Print any line with a substring containing a 'G' or 'D', followed by a sequence of digits and characters. This example uses character classes digit and alpha to match language- independent digit and alphabetic characters respectively: /(G|D)([[:digit:][:alpha:]]*)/ 5. Write any line in which the second field matches the regular expression and the fourth field does not: $2 ~ /xyz/ && $4 !~ /xyz/ 6. Write any line in which the second field contains a <backslash>: $2 ~ /\\/ 7. Write any line in which the second field contains a <backslash>. Note that <backslash>-escapes are interpreted twice; once in lexical processing of the string and once in processing the regular expression: $2 ~ "\\\\" 8. Write the second to the last and the last field in each line. Separate the fields by a <colon>: {OFS=":";print $(NF-1), $NF} 9. Write the line number and number of fields in each line. The three strings representing the line number, the <colon>, and the number of fields are concatenated and that string is written to standard output: {print NR ":" NF} 10. Write lines longer than 72 characters: length($0) > 72 11. Write the first two fields in opposite order separated by OFS: { print $2, $1 } 12. Same, with input fields separated by a <comma> or <space> and <tab> characters, or both: BEGIN { FS = ",[ \t]*|[ \t]+" } { print $2, $1 } 13. Add up the first column, print sum, and average: {s += $1 } END {print "sum is ", s, " average is", s/NR} 14. Write fields in reverse order, one per line (many lines out for each line in): { for (i = NF; i > 0; --i) print $i } 15. Write all lines between occurrences of the strings start and stop: /start/, /stop/ 16. Write all lines whose first field is different from the previous one: $1 != prev { print; prev = $1 } 17. Simulate echo: BEGIN { for (i = 1; i < ARGC; ++i) printf("%s%s", ARGV[i], i==ARGC-1?"\n":" ") } 18. Write the path prefixes contained in the PATH environment variable, one per line: BEGIN { n = split (ENVIRON["PATH"], path, ":") for (i = 1; i <= n; ++i) print path[i] } 19. If there is a file named input containing page headers of the form: Page # and a file named program that contains: /Page/ { $2 = n++; } { print } then the command line: awk -f program n=5 input prints the file input, filling in page numbers starting at 5. RATIONALE top This description is based on the new awk, ``nawk'', (see the referenced The AWK Programming Language), which introduced a number of new features to the historical awk: 1. New keywords: delete, do, function, return 2. New built-in functions: atan2, close, cos, gsub, match, rand, sin, srand, sub, system 3. New predefined variables: FNR, ARGC, ARGV, RSTART, RLENGTH, SUBSEP 4. New expression operators: ?, :, ,, ^ 5. The FS variable and the third argument to split, now treated as extended regular expressions. 6. The operator precedence, changed to more closely match the C language. Two examples of code that operate differently are: while ( n /= 10 > 1) ... if (!"wk" ~ /bwk/) ... Several features have been added based on newer implementations of awk: * Multiple instances of -f progfile are permitted. * The new option -v assignment. * The new predefined variable ENVIRON. * New built-in functions toupper and tolower. * More formatting capabilities are added to printf to match the ISO C standard. Earlier versions of this standard required implementations to support multiple adjacent <semicolon>s, lines with one or more <semicolon> before a rule (pattern-action pairs), and lines with only <semicolon>(s). These are not required by this standard and are considered poor programming practice, but can be accepted by an implementation of awk as an extension. The overall awk syntax has always been based on the C language, with a few features from the shell command language and other sources. Because of this, it is not completely compatible with any other language, which has caused confusion for some users. It is not the intent of the standard developers to address such issues. A few relatively minor changes toward making the language more compatible with the ISO C standard were made; most of these changes are based on similar changes in recent implementations, as described above. There remain several C-language conventions that are not in awk. One of the notable ones is the <comma> operator, which is commonly used to specify multiple expressions in the C language for statement. Also, there are various places where awk is more restrictive than the C language regarding the type of expression that can be used in a given context. These limitations are due to the different features that the awk language does provide. Regular expressions in awk have been extended somewhat from historical implementations to make them a pure superset of extended regular expressions, as defined by POSIX.12008 (see the Base Definitions volume of POSIX.12017, Section 9.4, Extended Regular Expressions). The main extensions are internationalization features and interval expressions. Historical implementations of awk have long supported <backslash>-escape sequences as an extension to extended regular expressions, and this extension has been retained despite inconsistency with other utilities. The number of escape sequences recognized in both extended regular expressions and strings has varied (generally increasing with time) among implementations. The set specified by POSIX.12008 includes most sequences known to be supported by popular implementations and by the ISO C standard. One sequence that is not supported is hexadecimal value escapes beginning with '\x'. This would allow values expressed in more than 9 bits to be used within awk as in the ISO C standard. However, because this syntax has a non- deterministic length, it does not permit the subsequent character to be a hexadecimal digit. This limitation can be dealt with in the C language by the use of lexical string concatenation. In the awk language, concatenation could also be a solution for strings, but not for extended regular expressions (either lexical ERE tokens or strings used dynamically as regular expressions). Because of this limitation, the feature has not been added to POSIX.12008. When a string variable is used in a context where an extended regular expression normally appears (where the lexical token ERE is used in the grammar) the string does not contain the literal <slash> characters. Some versions of awk allow the form: func name(args, ... ) { statements } This has been deprecated by the authors of the language, who asked that it not be specified. Historical implementations of awk produce an error if a next statement is executed in a BEGIN action, and cause awk to terminate if a next statement is executed in an END action. This behavior has not been documented, and it was not believed that it was necessary to standardize it. The specification of conversions between string and numeric values is much more detailed than in the documentation of historical implementations or in the referenced The AWK Programming Language. Although most of the behavior is designed to be intuitive, the details are necessary to ensure compatible behavior from different implementations. This is especially important in relational expressions since the types of the operands determine whether a string or numeric comparison is performed. From the perspective of an application developer, it is usually sufficient to expect intuitive behavior and to force conversions (by adding zero or concatenating a null string) when the type of an expression does not obviously match what is needed. The intent has been to specify historical practice in almost all cases. The one exception is that, in historical implementations, variables and constants maintain both string and numeric values after their original value is converted by any use. This means that referencing a variable or constant can have unexpected side-effects. For example, with historical implementations the following program: { a = "+2" b = 2 if (NR % 2) c = a + b if (a == b) print "numeric comparison" else print "string comparison" } would perform a numeric comparison (and output numeric comparison) for each odd-numbered line, but perform a string comparison (and output string comparison) for each even-numbered line. POSIX.12008 ensures that comparisons will be numeric if necessary. With historical implementations, the following program: BEGIN { OFMT = "%e" print 3.14 OFMT = "%f" print 3.14 } would output "3.140000e+00" twice, because in the second print statement the constant "3.14" would have a string value from the previous conversion. POSIX.12008 requires that the output of the second print statement be "3.140000". The behavior of historical implementations was seen as too unintuitive and unpredictable. It was pointed out that with the rules contained in early drafts, the following script would print nothing: BEGIN { y[1.5] = 1 OFMT = "%e" print y[1.5] } Therefore, a new variable, CONVFMT, was introduced. The OFMT variable is now restricted to affecting output conversions of numbers to strings and CONVFMT is used for internal conversions, such as comparisons or array indexing. The default value is the same as that for OFMT, so unless a program changes CONVFMT (which no historical program would do), it will receive the historical behavior associated with internal string conversions. The POSIX awk lexical and syntactic conventions are specified more formally than in other sources. Again the intent has been to specify historical practice. One convention that may not be obvious from the formal grammar as in other verbal descriptions is where <newline> characters are acceptable. There are several obvious placements such as terminating a statement, and a <backslash> can be used to escape <newline> characters between any lexical tokens. In addition, <newline> characters without <backslash> characters can follow a comma, an open brace, a logical AND operator ("&&"), a logical OR operator ("||"), the do keyword, the else keyword, and the closing parenthesis of an if, for, or while statement. For example: { print $1, $2 } The requirement that awk add a trailing <newline> to the program argument text is to simplify the grammar, making it match a text file in form. There is no way for an application or test suite to determine whether a literal <newline> is added or whether awk simply acts as if it did. POSIX.12008 requires several changes from historical implementations in order to support internationalization. Probably the most subtle of these is the use of the decimal-point character, defined by the LC_NUMERIC category of the locale, in representations of floating-point numbers. This locale-specific character is used in recognizing numeric input, in converting between strings and numeric values, and in formatting output. However, regardless of locale, the <period> character (the decimal-point character of the POSIX locale) is the decimal-point character recognized in processing awk programs (including assignments in command line arguments). This is essentially the same convention as the one used in the ISO C standard. The difference is that the C language includes the setlocale() function, which permits an application to modify its locale. Because of this capability, a C application begins executing with its locale set to the C locale, and only executes in the environment-specified locale after an explicit call to setlocale(). However, adding such an elaborate new feature to the awk language was seen as inappropriate for POSIX.12008. It is possible to execute an awk program explicitly in any desired locale by setting the environment in the shell. The undefined behavior resulting from NULs in extended regular expressions allows future extensions for the GNU gawk program to process binary data. The behavior in the case of invalid awk programs (including lexical, syntactic, and semantic errors) is undefined because it was considered overly limiting on implementations to specify. In most cases such errors can be expected to produce a diagnostic and a non-zero exit status. However, some implementations may choose to extend the language in ways that make use of certain invalid constructs. Other invalid constructs might be deemed worthy of a warning, but otherwise cause some reasonable behavior. Still other constructs may be very difficult to detect in some implementations. Also, different implementations might detect a given error during an initial parsing of the program (before reading any input files) while others might detect it when executing the program after reading some input. Implementors should be aware that diagnosing errors as early as possible and producing useful diagnostics can ease debugging of applications, and thus make an implementation more usable. The unspecified behavior from using multi-character RS values is to allow possible future extensions based on extended regular expressions used for record separators. Historical implementations take the first character of the string and ignore the others. Unspecified behavior when split(string,array,<null>) is used is to allow a proposed future extension that would split up a string into an array of individual characters. In the context of the getline function, equally good arguments for different precedences of the | and < operators can be made. Historical practice has been that: getline < "a" "b" is parsed as: ( getline < "a" ) "b" although many would argue that the intent was that the file ab should be read. However: getline < "x" + 1 parses as: getline < ( "x" + 1 ) Similar problems occur with the | version of getline, particularly in combination with $. For example: $"echo hi" | getline (This situation is particularly problematic when used in a print statement, where the |getline part might be a redirection of the print.) Since in most cases such constructs are not (or at least should not) be used (because they have a natural ambiguity for which there is no conventional parsing), the meaning of these constructs has been made explicitly unspecified. (The effect is that a conforming application that runs into the problem must parenthesize to resolve the ambiguity.) There appeared to be few if any actual uses of such constructs. Grammars can be written that would cause an error under these circumstances. Where backwards-compatibility is not a large consideration, implementors may wish to use such grammars. Some historical implementations have allowed some built-in functions to be called without an argument list, the result being a default argument list chosen in some ``reasonable'' way. Use of length as a synonym for length($0) is the only one of these forms that is thought to be widely known or widely used; this particular form is documented in various places (for example, most historical awk reference pages, although not in the referenced The AWK Programming Language) as legitimate practice. With this exception, default argument lists have always been undocumented and vaguely defined, and it is not at all clear how (or if) they should be generalized to user-defined functions. They add no useful functionality and preclude possible future extensions that might need to name functions without calling them. Not standardizing them seems the simplest course. The standard developers considered that length merited special treatment, however, since it has been documented in the past and sees possibly substantial use in historical programs. Accordingly, this usage has been made legitimate, but Issue 5 removed the obsolescent marking for XSI-conforming implementations and many otherwise conforming applications depend on this feature. In sub and gsub, if repl is a string literal (the lexical token STRING), then two consecutive <backslash> characters should be used in the string to ensure a single <backslash> will precede the <ampersand> when the resultant string is passed to the function. (For example, to specify one literal <ampersand> in the replacement string, use gsub(ERE, "\\&").) Historically, the only special character in the repl argument of sub and gsub string functions was the <ampersand> ('&') character and preceding it with the <backslash> character was used to turn off its special meaning. The description in the ISO POSIX2:1993 standard introduced behavior such that the <backslash> character was another special character and it was unspecified whether there were any other special characters. This description introduced several portability problems, some of which are described below, and so it has been replaced with the more historical description. Some of the problems include: * Historically, to create the replacement string, a script could use gsub(ERE, "\\&"), but with the ISO POSIX2:1993 standard wording, it was necessary to use gsub(ERE, "\\\\&"). The <backslash> characters are doubled here because all string literals are subject to lexical analysis, which would reduce each pair of <backslash> characters to a single <backslash> before being passed to gsub. * Since it was unspecified what the special characters were, for portable scripts to guarantee that characters are printed literally, each character had to be preceded with a <backslash>. (For example, a portable script had to use gsub(ERE, "\\h\\i") to produce a replacement string of "hi".) The description for comparisons in the ISO POSIX2:1993 standard did not properly describe historical practice because of the way numeric strings are compared as numbers. The current rules cause the following code: if (0 == "000") print "strange, but true" else print "not true" to do a numeric comparison, causing the if to succeed. It should be intuitively obvious that this is incorrect behavior, and indeed, no historical implementation of awk actually behaves this way. To fix this problem, the definition of numeric string was enhanced to include only those values obtained from specific circumstances (mostly external sources) where it is not possible to determine unambiguously whether the value is intended to be a string or a numeric. Variables that are assigned to a numeric string shall also be treated as a numeric string. (For example, the notion of a numeric string can be propagated across assignments.) In comparisons, all variables having the uninitialized value are to be treated as a numeric operand evaluating to the numeric value zero. Uninitialized variables include all types of variables including scalars, array elements, and fields. The definition of an uninitialized value in Variables and Special Variables is necessary to describe the value placed on uninitialized variables and on fields that are valid (for example, < $NF) but have no characters in them and to describe how these variables are to be used in comparisons. A valid field, such as $1, that has no characters in it can be obtained from an input line of "\t\t" when FS='\t'. Historically, the comparison ($1<10) was done numerically after evaluating $1 to the value zero. The phrase ``... also shall have the numeric value of the numeric string'' was removed from several sections of the ISO POSIX2:1993 standard because is specifies an unnecessary implementation detail. It is not necessary for POSIX.12008 to specify that these objects be assigned two different values. It is only necessary to specify that these objects may evaluate to two different values depending on context. Historical implementations of awk did not parse hexadecimal integer or floating constants like "0xa" and "0xap0". Due to an oversight, the 2001 through 2004 editions of this standard required support for hexadecimal floating constants. This was due to the reference to atof(). This version of the standard allows but does not require implementations to use atof() and includes a description of how floating-point numbers are recognized as an alternative to match historic behavior. The intent of this change is to allow implementations to recognize floating-point constants according to either the ISO/IEC 9899:1990 standard or ISO/IEC 9899:1999 standard, and to allow (but not require) implementations to recognize hexadecimal integer constants. Historical implementations of awk did not support floating-point infinities and NaNs in numeric strings; e.g., "-INF" and "NaN". However, implementations that use the atof() or strtod() functions to do the conversion picked up support for these values if they used a ISO/IEC 9899:1999 standard version of the function instead of a ISO/IEC 9899:1990 standard version. Due to an oversight, the 2001 through 2004 editions of this standard did not allow support for infinities and NaNs, but in this revision support is allowed (but not required). This is a silent change to the behavior of awk programs; for example, in the POSIX locale the expression: ("-INF" + 0 < 0) formerly had the value 0 because "-INF" converted to 0, but now it may have the value 0 or 1. FUTURE DIRECTIONS top A future version of this standard may require the "!=" and "==" operators to perform string comparisons by checking if the strings are identical (and not by checking if they collate equally). SEE ALSO top Section 1.3, Grammar Conventions, grep(1p), lex(1p), sed(1p) The Base Definitions volume of POSIX.12017, Chapter 5, File Format Notation, Section 6.1, Portable Character Set, Chapter 8, Environment Variables, Chapter 9, Regular Expressions, Section 12.2, Utility Syntax Guidelines The System Interfaces volume of POSIX.12017, atof(3p), exec(1p), isspace(3p), popen(3p), setlocale(3p), strtod(3p) COPYRIGHT top Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html . IEEE/The Open Group 2017 AWK(1P) Pages that refer to this page: bc(1p), colrm(1), join(1p), printf(1p), sed(1p) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. file(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training file(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | FILES | EXIT STATUS | EXAMPLES | SEE ALSO | STANDARDS CONFORMANCE | SECURITY | MAGIC DIRECTORY | HISTORY | LEGAL NOTICE | BUGS | TODO | AVAILABILITY | COLOPHON FILE(1) General Commands Manual FILE(1) NAME top file determine file type SYNOPSIS top [-bcdEhiklLNnprsSvzZ0] [--apple] [--exclude-quiet] [--extension] [--mime-encoding] [--mime-type] [-e testname] [-F separator] [-f namefile] [-m magicfiles] [-P name=value] file ... -C [-m magicfiles] [--help] DESCRIPTION top This manual page documents version 5.45 of the command. tests each argument in an attempt to classify it. There are three sets of tests, performed in this order: filesystem tests, magic tests, and language tests. The first test that succeeds causes the file type to be printed. The type printed will usually contain one of the words text (the file contains only printing characters and a few common control characters and is probably safe to read on an ASCII terminal), executable (the file contains the result of compiling a program in a form understandable to some UNIX kernel or another), or data meaning anything else (data is usually binary or non- printable). Exceptions are well-known file formats (core files, tar archives) that are known to contain binary data. When modifying magic files or the program itself, make sure to preserve these keywords. Users depend on knowing that all the readable files in a directory have the word text printed. Don't do as Berkeley did and change shell commands text to shell script. The filesystem tests are based on examining the return from a stat(2) system call. The program checks to see if the file is empty, or if it's some sort of special file. Any known file types appropriate to the system you are running on (sockets, symbolic links, or named pipes (FIFOs) on those systems that implement them) are intuited if they are defined in the system header file <sys/stat.h>. The magic tests are used to check for files with data in particular fixed formats. The canonical example of this is a binary executable (compiled program) a.out file, whose format is defined in <elf.h>, <a.out.h> and possibly <exec.h> in the standard include directory. These files have a magic number stored in a particular place near the beginning of the file that tells the UNIX operating system that the file is a binary executable, and which of several types thereof. The concept of a magic number has been applied by extension to data files. Any file with some invariant identifier at a small fixed offset into the file can usually be described in this way. The information identifying these files is read from the compiled magic file /usr/local/share/misc/magic.mgc, or the files in the directory /usr/local/share/misc/magic if the compiled file does not exist. In addition, if $HOME/.magic.mgc or $HOME/.magic exists, it will be used in preference to the system magic files. If a file does not match any of the entries in the magic file, it is examined to see if it seems to be a text file. ASCII, ISO-8859-x, non-ISO 8-bit extended-ASCII character sets (such as those used on Macintosh and IBM PC systems), UTF-8-encoded Unicode, UTF-16-encoded Unicode, and EBCDIC character sets can be distinguished by the different ranges and sequences of bytes that constitute printable text in each set. If a file passes any of these tests, its character set is reported. ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are identified as text because they will be mostly readable on nearly any terminal; UTF-16 and EBCDIC are only character data because, while they contain text, it is text that will require translation before it can be read. In addition, will attempt to determine other characteristics of text-type files. If the lines of a file are terminated by CR, CRLF, or NEL, instead of the Unix-standard LF, this will be reported. Files that contain embedded escape sequences or overstriking will also be identified. Once has determined the character set used in a text-type file, it will attempt to determine in what language the file is written. The language tests look for particular strings (cf. <names.h>) that can appear anywhere in the first few blocks of a file. For example, the keyword .br indicates that the file is most likely a troff(1) input file, just as the keyword struct indicates a C program. These tests are less reliable than the previous two groups, so they are performed last. The language test routines also test for some miscellany (such as tar(1) archives, JSON files). Any file that cannot be identified as having been written in any of the character sets listed above is simply said to be data. OPTIONS top --apple Causes the command to output the file type and creator code as used by older MacOS versions. The code consists of eight letters, the first describing the file type, the latter the creator. This option works properly only for file formats that have the apple-style output defined. -b, --brief Do not prepend filenames to output lines (brief mode). -C, --compile Write a magic.mgc output file that contains a pre-parsed version of the magic file or directory. -c, --checking-printout Cause a checking printout of the parsed form of the magic file. This is usually used in conjunction with the -m option to debug a new magic file before installing it. -d Prints internal debugging information to stderr. -E On filesystem errors (file not found etc), instead of handling the error as regular output as POSIX mandates and keep going, issue an error message and exit. -e, --exclude testname Exclude the test named in testname from the list of tests made to determine the file type. Valid test names are: apptype EMX application type (only on EMX). ascii Various types of text files (this test will try to guess the text encoding, irrespective of the setting of the encoding option). encoding Different text encodings for soft magic tests. tokens Ignored for backwards compatibility. cdf Prints details of Compound Document Files. compress Checks for, and looks inside, compressed files. csv Checks Comma Separated Value files. elf Prints ELF file details, provided soft magic tests are enabled and the elf magic is found. json Examines JSON (RFC-7159) files by parsing them for compliance. soft Consults magic files. simh Examines SIMH tape files. tar Examines tar files by verifying the checksum of the 512 byte tar header. Excluding this test can provide more detailed content description by using the soft magic method. text A synonym for ascii. --exclude-quiet Like --exclude but ignore tests that does not know about. This is intended for compatibility with older versions of . --extension Print a slash-separated list of valid extensions for the file type found. -F, --separator separator Use the specified string as the separator between the filename and the file result returned. Defaults to :. -f, --files-from namefile Read the names of the files to be examined from namefile (one per line) before the argument list. Either namefile or at least one filename argument must be present; to test the standard input, use - as a filename argument. Please note that namefile is unwrapped and the enclosed filenames are processed when this option is encountered and before any further options processing is done. This allows one to process multiple lists of files with different command line arguments on the same invocation. Thus if you want to set the delimiter, you need to do it before you specify the list of files, like: -F @ -f namefile, instead of: -f namefile -F @. -h, --no-dereference This option causes symlinks not to be followed (on systems that support symbolic links). This is the default if the environment variable POSIXLY_CORRECT is not defined. -i, --mime Causes the command to output mime type strings rather than the more traditional human readable ones. Thus it may say text/plain; charset=us-ascii rather than ASCII text. --mime-type, --mime-encoding Like -i, but print only the specified element(s). -k, --keep-going Don't stop at the first match, keep going. Subsequent matches will be have the string \012- prepended. (If you want a newline, see the -r option.) The magic pattern with the highest strength (see the -l option) comes first. -l, --list Shows a list of patterns and their strength sorted descending by magic(4) strength which is used for the matching (see also the -k option). -L, --dereference This option causes symlinks to be followed, as the like- named option in ls(1) (on systems that support symbolic links). This is the default if the environment variable POSIXLY_CORRECT is defined. -m, --magic-file magicfiles Specify an alternate list of files and directories containing magic. This can be a single item, or a colon- separated list. If a compiled magic file is found alongside a file or directory, it will be used instead. -N, --no-pad Don't pad filenames so that they align in the output. -n, --no-buffer Force stdout to be flushed after checking each file. This is only useful if checking a list of files. It is intended to be used by programs that want filetype output from a pipe. -p, --preserve-date On systems that support utime(3) or utimes(2), attempt to preserve the access time of files analyzed, to pretend that never read them. -P, --parameter name=value Set various parameter limits. Name Default Explanation bytes 1M max number of bytes to read from file elf_notes 256 max ELF notes processed elf_phnum 2K max ELF program sections processed elf_shnum 32K max ELF sections processed elf_shsize 128MB max ELF section size processed encoding 65K max number of bytes to determine encoding indir 50 recursion limit for indirect magic name 50 use count limit for name/use magic regex 8K length limit for regex searches -r, --raw Don't translate unprintable characters to \ooo. Normally translates unprintable characters to their octal representation. -s, --special-files Normally, only attempts to read and determine the type of argument files which stat(2) reports are ordinary files. This prevents problems, because reading special files may have peculiar consequences. Specifying the -s option causes to also read argument files which are block or character special files. This is useful for determining the filesystem types of the data in raw disk partitions, which are block special files. This option also causes to disregard the file size as reported by stat(2) since on some systems it reports a zero size for raw disk partitions. -S, --no-sandbox On systems where libseccomp (https://github.com/seccomp/libseccomp ) is available, the -S option disables sandboxing which is enabled by default. This option is needed for to execute external decompressing programs, i.e. when the -z option is specified and the built-in decompressors are not available. On systems where sandboxing is not available, this option has no effect. -v, --version Print the version of the program and exit. -z, --uncompress Try to look inside compressed files. -Z, --uncompress-noreport Try to look inside compressed files, but report information about the contents only not the compression. -0, --print0 Output a null character \0 after the end of the filename. Nice to cut(1) the output. This does not affect the separator, which is still printed. If this option is repeated more than once, then prints just the filename followed by a NUL followed by the description (or ERROR: text) followed by a second NUL for each entry. --help Print a help message and exit. ENVIRONMENT top The environment variable MAGIC can be used to set the default magic file name. If that variable is set, then will not attempt to open $HOME/.magic. adds .mgc to the value of this variable as appropriate. The environment variable POSIXLY_CORRECT controls (on systems that support symbolic links), whether will attempt to follow symlinks or not. If set, then follows symlink, otherwise it does not. This is also controlled by the -L and -h options. FILES top /usr/local/share/misc/magic.mgc Default compiled list of magic. /usr/local/share/misc/magic Directory containing default magic files. EXIT STATUS top will exit with 0 if the operation was successful or >0 if an error was encountered. The following errors cause diagnostic messages, but don't affect the program exit code (as POSIX requires), unless -E is specified: A file cannot be found There is no permission to read a file The file type cannot be determined EXAMPLES top $ file file.c file /dev/{wd0a,hda} file.c: C program text file: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), stripped /dev/wd0a: block special (0/0) /dev/hda: block special (3/0) $ file -s /dev/wd0{b,d} /dev/wd0b: data /dev/wd0d: x86 boot sector $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10} /dev/hda: x86 boot sector /dev/hda1: Linux/i386 ext2 filesystem /dev/hda2: x86 boot sector /dev/hda3: x86 boot sector, extended partition table /dev/hda4: Linux/i386 ext2 filesystem /dev/hda5: Linux/i386 swap file /dev/hda6: Linux/i386 swap file /dev/hda7: Linux/i386 swap file /dev/hda8: Linux/i386 swap file /dev/hda9: empty /dev/hda10: empty $ file -i file.c file /dev/{wd0a,hda} file.c: text/x-c file: application/x-executable /dev/hda: application/x-not-regular-file /dev/wd0a: application/x-not-regular-file SEE ALSO top hexdump(1), od(1), strings(1), magic(4) STANDARDS CONFORMANCE top This program is believed to exceed the System V Interface Definition of FILE(CMD), as near as one can determine from the vague language contained therein. Its behavior is mostly compatible with the System V program of the same name. This version knows more magic, however, so it will produce different (albeit more accurate) output in many cases. The one significant difference between this version and System V is that this version treats any white space as a delimiter, so that spaces in pattern strings must be escaped. For example, >10 string language impress (imPRESS data) in an existing magic file would have to be changed to >10 string language\ impress (imPRESS data) In addition, in this version, if a pattern string contains a backslash, it must be escaped. For example 0 string \begindata Andrew Toolkit document in an existing magic file would have to be changed to 0 string \\begindata Andrew Toolkit document SunOS releases 3.2 and later from Sun Microsystems include a command derived from the System V one, but with some extensions. This version differs from Sun's only in minor ways. It includes the extension of the & operator, used as, for example, >16 long&0x7fffffff >0 not stripped SECURITY top On systems where libseccomp (https://github.com/seccomp/libseccomp ) is available, is enforces limiting system calls to only the ones necessary for the operation of the program. This enforcement does not provide any security benefit when is asked to decompress input files running external programs with the -z option. To enable execution of external decompressors, one needs to disable sandboxing using the -S option. MAGIC DIRECTORY top The magic file entries have been collected from various sources, mainly USENET, and contributed by various authors. Christos Zoulas (address below) will collect additional or corrected magic file entries. A consolidation of magic file entries will be distributed periodically. The order of entries in the magic file is significant. Depending on what system you are using, the order that they are put together may be incorrect. If your old command uses a magic file, keep the old magic file around for comparison purposes (rename it to /usr/local/share/misc/magic.orig). HISTORY top There has been a command in every UNIX since at least Research Version 4 (man page dated November, 1973). The System V version introduced one significant major change: the external list of magic types. This slowed the program down slightly but made it a lot more flexible. This program, based on the System V version, was written by Ian Darwin ian@darwinsys.com without looking at anybody else's source code. John Gilmore revised the code extensively, making it better than the first version. Geoff Collyer found several inadequacies and provided some magic file entries. Contributions of the & operator by Rob McMahon, cudcv@warwick.ac.uk, 1989. Guy Harris, guy@netapp.com, made many changes from 1993 to the present. Primary development and maintenance from 1990 to the present by Christos Zoulas christos@astron.com. Altered by Chris Lowth chris@lowth.com, 2000: handle the -i option to output mime type strings, using an alternative magic file and internal logic. Altered by Eric Fischer enf@pobox.com, July, 2000, to identify character codes and attempt to identify the languages of non- ASCII files. Altered by Reuben Thomas rrt@sc3d.org, 2007-2011, to improve MIME support, merge MIME and non-MIME magic, support directories as well as files of magic, apply many bug fixes, update and fix a lot of magic, improve the build system, improve the documentation, and rewrite the Python bindings in pure Python. The list of contributors to the magic directory (magic files) is too long to include here. You know who you are; thank you. Many contributors are listed in the source files. LEGAL NOTICE top Copyright (c) Ian F. Darwin, Toronto, Canada, 1986-1999. Covered by the standard Berkeley Software Distribution copyright; see the file COPYING in the source distribution. The files tar.h and is_tar.c were written by John Gilmore from his public-domain tar(1) program, and are not covered by the above license. BUGS top Please report bugs and send patches to the bug tracker at https://bugs.astron.com/ or the mailing list at file@astron.com (visit https://mailman.astron.com/mailman/listinfo/file first to subscribe). TODO top Fix output so that tests for MIME and APPLE flags are not needed all over the place, and actual output is only done in one place. This needs a design. Suggestion: push possible outputs on to a list, then pick the last-pushed (most specific, one hopes) value at the end, or use a default if the list is empty. This should not slow down evaluation. The handling of MAGIC_CONTINUE and printing \012- between entries is clumsy and complicated; refactor and centralize. Some of the encoding logic is hard-coded in encoding.c and can be moved to the magic files if we had a !:charset annotation. Continue to squash all magic bugs. See Debian BTS for a good source. Store arbitrarily long strings, for example for %s patterns, so that they can be printed out. Fixes Debian bug #271672. This can be done by allocating strings in a string pool, storing the string pool at the end of the magic file and converting all the string pointers to relative offsets from the string pool. Add syntax for relative offsets after current level (Debian bug #466037). Make file -ki work, i.e. give multiple MIME types. Add a zip library so we can peek inside Office2007 documents to print more details about their contents. Add an option to print URLs for the sources of the file descriptions. Combine script searches and add a way to map executable names to MIME types (e.g. have a magic value for !:mime which causes the resulting string to be looked up in a table). This would avoid adding the same magic repeatedly for each new hash-bang interpreter. When a file descriptor is available, we can skip and adjust the buffer instead of the hacky buffer management we do now. Fix name and use to check for consistency at compile time (duplicate name, use pointing to undefined name ). Make name / use more efficient by keeping a sorted list of names. Special-case ^ to flip endianness in the parser so that it does not have to be escaped, and document it. If the offsets specified internally in the file exceed the buffer size ( HOWMANY variable in file.h), then we don't seek to that offset, but we give up. It would be better if buffer managements was done when the file descriptor is available so we can seek around the file. One must be careful though because this has performance and thus security considerations, because one can slow down things by repeatedly seeking. There is support now for keeping separate buffers and having offsets from the end of the file, but the internal buffer management still needs an overhaul. AVAILABILITY top You can obtain the original author's latest version by anonymous FTP on ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz. COLOPHON top This page is part of the file (a file type guesser) project. Information about the project can be found at http://www.darwinsys.com/file/. If you have a bug report for this manual page, see http://bugs.gw.com/my_view_page.php. This page was obtained from the project's upstream Git read-only mirror of the CVS repository https://github.com/glensc/file on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-21.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org GNU May 21, 2023 FILE(1) Pages that refer to this page: dh_installmanpages(1), dh_strip(1), ippeveprinter(1), pmcd(1), scr_dump(5), term(5), suffixes(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. column(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training column(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | HISTORY | BUGS | EXAMPLES | SEE ALSO | REPORTING BUGS | AVAILABILITY COLUMN(1) User Commands COLUMN(1) NAME top column - columnate lists SYNOPSIS top column [options] [file ...] DESCRIPTION top The column utility formats its input into multiple columns. The util support three modes: columns are filled before rows This is the default mode (required by backward compatibility). rows are filled before columns This mode is enabled by option -x, --fillrows table Determine the number of columns the input contains and create a table. This mode is enabled by option -t, --table and columns formatting is possible to modify by --table-* options. Use this mode if not sure. The output is aligned to the terminal width in interactive mode and the 80 columns in non-interactive mode (see --output-width for more details). Input is taken from file, or otherwise from standard input. Empty lines are ignored and all invalid multibyte sequences are encoded by x<hex> convention. OPTIONS top The argument columns for --table-* options is a comma separated list of the column names as defined by --table-columns, or names defined by --table-column or its column number in order as specified by input. Its possible to mix names and numbers. The special placeholder '0' (e.g. -R0) may be used to specify all columns and '-1' (e.g. -R -1) to specify the last visible column. Its possible to use ranges like '1-5' when addressing columns by numbers. -J, --json Use JSON output format to print the table, the option --table-columns is required and the option --table-name is recommended. -c, --output-width width Output is formatted to a width specified as number of characters. The original name of this option is --columns; this name is deprecated since v2.30. Note that input longer than width is not truncated by default. The default is a terminal width and the 80 columns in non-interactive mode. The column headers are never truncated. The placeholder "unlimited" (or 0) is possible to use to not restrict output width. This is recommended for example when output to the files rather than on terminal. -d, --table-noheadings Do not print header. This option allows the use of logical column names on the command line, but keeps the header hidden when printing the table. -o, --output-separator string Specify the columns delimiter for table output (default is two spaces). -s, --separator separators Specify the possible input item delimiters (default is whitespace). -t, --table Determine the number of columns the input contains and create a table. Columns are delimited with whitespace, by default, or with the characters supplied using the --output-separator option. Table output is useful for pretty-printing. -C, --table-column properties Define one column by comma separated list of column attributes. This option can be used more than once, every use defines just one column. The properties replace some of --table- options. For example --table-column name=FOO,right define one column where text is aligned to right. The option is mutually exclusive to --table-columns. The currently supported attributes are: name=string Specifies column name. trunc The column text can be truncated when necessary. The same as --table-truncate. right Right align text in the specified columns. The same as --table-right. width=number Specifies column width. The width is used as a hint only. The width is strictly followed only when strictwidth attribute is used too. strictwidth Strictly follow column width= setting. noextreme Specify columns where is possible to ignore unusually long cells. See --table-noextreme for more details. wrap Specify columns where is possible to use multi-line cell for long text when necessary. See --table-wrap. hide Dont print specified columns. See --table-hide. json=type Define column type for JSON output, Supported are string, number and boolean. -N, --table-columns names Specify the columns names by comma separated list of names. The names are used for the table header or to address column in option argument. See also --table-column. -l, --table-columns-limit number Specify maximal number of the input columns. The last column will contain all remaining line data if the limit is smaller than the number of the columns in the input data. -R, --table-right columns Right align text in the specified columns. -T, --table-truncate columns Specify columns where text can be truncated when necessary, otherwise very long table entries may be printed on multiple lines. -E, --table-noextreme columns Specify columns where is possible to ignore unusually long (longer than average) cells when calculate column width. The option has impact to the width calculation and table formatting, but the printed text is not affected. The option is used for the last visible column by default. -e, --table-header-repeat Print header line for each page. -W, --table-wrap columns Specify columns where is possible to use multi-line cell for long text when necessary. -H, --table-hide columns Dont print specified columns. The special placeholder '-' may be used to hide all unnamed columns (see --table-columns). -O, --table-order columns Specify columns order on output. -n, --table-name name Specify the table name used for JSON output. The default is "table". -m, --table-maxout Fill all available space on output. -L, --keep-empty-lines Preserve whitespace-only lines in the input. The default is ignore empty lines at all. This options original name was --table-empty-lines but is now deprecated because it gives the false impression that the option only applies to table mode. -r, --tree column Specify column to use tree-like output. Note that the circular dependencies and other anomalies in child and parent relation are silently ignored. -i, --tree-id column Specify column with line ID to create child-parent relation. -p, --tree-parent column Specify column with parent ID to create child-parent relation. -x, --fillrows Fill rows before filling columns. -h, --help Display help text and exit. -V, --version Print version and exit. ENVIRONMENT top The environment variable COLUMNS is used to determine the size of the screen if no other information is available. HISTORY top The column command appeared in 4.3BSD-Reno. BUGS top Version 2.23 changed the -s option to be non-greedy, for example: printf "a:b:c\n1::3\n" | column -t -s ':' Old output: a b c 1 3 New output (since util-linux 2.23): a b c 1 3 Historical versions of this tool indicated that "rows are filled before columns" by default, and that the -x option reverses this. This wording did not reflect the actual behavior, and it has since been corrected (see above). Other implementations of column may continue to use the older documentation, but the behavior should be identical in any case. EXAMPLES top Print fstab with header line and align number to the right: sed 's/#.*//' /etc/fstab | column --table --table-columns SOURCE,TARGET,TYPE,OPTIONS,PASS,FREQ --table-right PASS,FREQ Print fstab and hide unnamed columns: sed 's/#.*//' /etc/fstab | column --table --table-columns SOURCE,TARGET,TYPE --table-hide - Print a tree: echo -e '1 0 A\n2 1 AA\n3 1 AB\n4 2 AAA\n5 2 AAB' | column --tree-id 1 --tree-parent 2 --tree 3 1 0 A 2 1 |-AA 4 2 | |-AAA 5 2 | `-AAB 3 1 `-AB SEE ALSO top colrm(1), ls(1), paste(1), sort(1) REPORTING BUGS top For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues. AVAILABILITY top The column command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at https://www.kernel.org/pub/linux/utils/util-linux/. If you have a bug report for this manual page, send it to util-linux@vger.kernel.org. This page was obtained from the project's upstream Git repository git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-12-14.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org util-linux 2.39.594-1e0ad 2023-07-19 COLUMN(1) Pages that refer to this page: colrm(1) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Compare column 3 with column 2 of the next line in "file" and format output as a table Bash Command:<START>awk 'NR==1 { print; next } { print $0, ($1 == a && $2 == b) ? "equal" : "not_equal"; a = $1; b = $3 }' file | column -t<END>

Compare each .xml file under the current directory with a file of the same name in "/destination/dir/2"

find . -name *.xml -exec diff {} /destination/dir/2/{} \;

['find', 'diff']

Output a Bash command to accomplish the following task. Task: Compare each .xml file under the current directory with a file of the same name in "/destination/dir/2" Bash Command:<START>find . -name *.xml -exec diff {} /destination/dir/2/{} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: # find\n\n> Find files or directories under a directory tree, recursively.\n> More information: <https://manned.org/find>.\n\n- Find files by extension:\n\n`find {{root_path}} -name '{{*.ext}}'`\n\n- Find files matching multiple path/name patterns:\n\n`find {{root_path}} -path '{{**/path/**/*.ext}}' -or -name '{{*pattern*}}'`\n\n- Find directories matching a given name, in case-insensitive mode:\n\n`find {{root_path}} -type d -iname '{{*lib*}}'`\n\n- Find files matching a given pattern, excluding specific paths:\n\n`find {{root_path}} -name '{{*.py}}' -not -path '{{*/site-packages/*}}'`\n\n- Find files matching a given size range, limiting the recursive depth to "1":\n\n`find {{root_path}} -maxdepth 1 -size {{+500k}} -size {{-10M}}`\n\n- Run a command for each file (use `{}` within the command to access the filename):\n\n`find {{root_path}} -name '{{*.ext}}' -exec {{wc -l}} {} \;`\n\n- Find all files modified today and pass the results to a single command as arguments:\n\n`find {{root_path}} -daystart -mtime {{-1}} -exec {{tar -cvf archive.tar}} {} \+`\n\n- Find empty (0 byte) files and delete them:\n\n`find {{root_path}} -type {{f}} -empty -delete`\n # diff\n\n> Compare files and directories.\n> More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.\n\n- Compare files (lists changes to turn `old_file` into `new_file`):\n\n`diff {{old_file}} {{new_file}}`\n\n- Compare files, ignoring [w]hite spaces:\n\n`diff {{-w|--ignore-all-space}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences side by side:\n\n`diff {{-y|--side-by-side}} {{old_file}} {{new_file}}`\n\n- Compare files, showing the differences in [u]nified format (as used by `git diff`):\n\n`diff {{-u|--unified}} {{old_file}} {{new_file}}`\n\n- Compare directories [r]ecursively (shows names for differing files/directories as well as changes made to files):\n\n`diff {{-r|--recursive}} {{old_directory}} {{new_directory}}`\n\n- Compare directories, only showing the names of files that differ:\n\n`diff {{-r|--recursive}} {{-q|--brief}} {{old_directory}} {{new_directory}}`\n\n- Create a patch file for Git from the differences of two text files, treating nonexistent files as empty:\n\n`diff {{-a|--text}} {{-u|--unified}} {{-N|--new-file}} {{old_file}} {{new_file}} > {{diff.patch}}`\n\n- Compare files, showing output in color and try hard to find smaller set of changes:\n\n`diff {{-d|--minimal}} --color=always {{old_file}} {{new_file}}`\n Task: Compare each .xml file under the current directory with a file of the same name in "/destination/dir/2" Bash Command:<START>find . -name *.xml -exec diff {} /destination/dir/2/{} \;<END>

Use the provided context to output a Bash command that accomplishes the following task. Context: find(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training find(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXPRESSION | UNUSUAL FILENAMES | STANDARDS CONFORMANCE | ENVIRONMENT VARIABLES | EXAMPLES | EXIT STATUS | HISTORY | COMPATIBILITY | NON-BUGS | BUGS | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON FIND(1) General Commands Manual FIND(1) NAME top find - search for files in a directory hierarchy SYNOPSIS top find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression] DESCRIPTION top This manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name. If no starting-point is specified, `.' is assumed. If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils. That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information. OPTIONS top The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'. That argument and any following arguments are taken to be the expression describing what is to be searched for. If no paths are given, the current directory is used. If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway). This manual page talks about `options' within the expression list. These options control the behaviour of find but are specified immediately after the last path name. The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all. A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-'). Now, if a path argument would start with a `-', then find would treat it as expression argument instead. Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'. Alternatively, it is generally safe though non-portable to use the GNU option -files0-from to pass arbitrary starting points to find. -P Never follow symbolic links. This is the default behaviour. When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself. -L Follow symbolic links. When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points). Use of this option implies -noleaf. If you later use the -P option, -noleaf will still be in effect. If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched. When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour. Using -L causes the -lname and -ilname predicates always to return false. -H Do not follow symbolic links, except while processing the command line arguments. When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself. The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved. For that situation, the information used is taken from whatever the link points to (that is, the link is followed). The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined. If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this). If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect. Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified. GNU find frequently stats files during the processing of the command line itself, before any searching has begun. These options also affect how those arguments are processed. Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering. In each case, the file specified on the command line will have been examined and some of its properties will have been saved. If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link. Otherwise, it will be taken from the properties of the file the link points to. If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used. When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points. The same consideration applies to -newerXY, -anewer and -cnewer. The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not). -D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want. The list of debug options should be comma separated. Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help. Valid debug options include exec Show diagnostic information relating to -exec, -execdir, -ok and -okdir opt Prints diagnostic information relating to the optimisation of the expression tree; see the -O option. rates Prints a summary indicating how often each predicate succeeded or failed. search Navigate the directory tree verbosely. stat Print messages as files are examined with the stat and lstat system calls. The find program tries to minimise such calls. tree Show the expression tree in its original and optimised form. all Enable all of the other debug options (but help). help Explain the debugging options. -Olevel Enables query optimisation. The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other. The optimisations performed at each optimisation level are as follows. 0 Equivalent to optimisation level 1. 1 This is the default optimisation level and corresponds to the traditional behaviour. Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first. 2 Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode. On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first. If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false. 3 At this optimisation level, the full cost-based query optimiser is enabled. The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary. Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier. The cost-based optimiser has a fixed idea of how likely any given test is to succeed. In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c). The cost-based optimiser is currently being evaluated. If it does not actually improve the performance of find, it will be removed again. Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time. However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series. The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same. EXPRESSION top The part of the command line after the list of starting points is the expression. This is a kind of query specification describing how we match files and what we do with the files that were matched. An expression is composed of a sequence of things: Tests Tests return a true or false value, usually on the basis of some property of a file we are considering. The -empty test for example is true only when the current file is empty. Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful. The -print action for example prints the name of the current file on the standard output. Global options Global options affect the operation of tests and actions specified on any part of the command line. Global options always return true. The -depth option for example makes find traverse the file system in a depth-first order. Positional options Positional options affect only tests or actions which follow them. Positional options always return true. The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line. Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND). Where an operator is missing, -a is assumed. The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit. Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf. The -delete action also acts like an option (since it implies -depth). POSITIONAL OPTIONS Positional options always return true. They affect only tests occurring later on the command line. -daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line. -follow Deprecated; use the -L option instead. Dereference symbolic links. Implies -noleaf. The -follow option affects only those tests which appear after it on the command line. Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links. The same consideration applies to -newerXY, -anewer and -cnewer. Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself. Using -follow causes the -lname and -ilname predicates always to return false. -regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line. To see which regular expression types are known, use -regextype help. The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression. -warn, -nowarn Turn warning messages on or off. These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories. The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise. If a warning message relating to command-line usage is produced, the exit status of find is not affected. If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active. GLOBAL OPTIONS Global options always return true. Global options take effect even for tests which occur earlier on the command line. To prevent confusion, global options should be specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing. The global options occur after the list of start points, and so are not the same kind of option as -L, for example. -d A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD. -depth Process each directory's contents before the directory itself. The -delete action also implies -depth. -files0-from file Read the starting points from file instead of getting them on the command line. In contrast to the known limitations of passing starting points via arguments on the command line, namely the limitation of the amount of file names, and the inherent ambiguity of file names clashing with option names, using this option allows to safely pass an arbitrary number of starting points to find. Using this option and passing starting points on the command line is mutually exclusive, and is therefore not allowed at the same time. The file argument is mandatory. One can use -files0-from - to read the list of starting points from the standard input stream, and e.g. from a pipe. In this case, the actions -ok and -okdir are not allowed, because they would obviously interfere with reading from standard input in order to get a user confirmation. The starting points in file have to be separated by ASCII NUL characters. Two consecutive NUL characters, i.e., a starting point with a Zero-length file name is not allowed and will lead to an error diagnostic followed by a non- Zero exit code later. In the case the given file is empty, find does not process any starting point and therefore will exit immediately after parsing the program arguments. This is unlike the standard invocation where find assumes the current directory as starting point if no path argument is passed. The processing of the starting points is otherwise as usual, e.g. find will recurse into subdirectories unless otherwise prevented. To process only the starting points, one can additionally pass -maxdepth 0. Further notes: if a file is listed more than once in the input file, it is unspecified whether it is visited more than once. If the file is mutated during the operation of find, the result is unspecified as well. Finally, the seek position within the named file at the time find exits, be it with -quit or in any other way, is also unspecified. By "unspecified" here is meant that it may or may not work or do any specific thing, and that the behavior may change from platform to platform, or from findutils release to release. -help, --help Print a summary of the command-line usage of find and exit. -ignore_readdir_race Normally, find will emit an error message when it fails to stat a file. If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line. This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it). Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true. -maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points. Using -maxdepth 0 means only apply the tests and actions to the starting- points themselves. -mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer). Using -mindepth 1 means process all files except the starting-points. -mount Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find. -noignore_readdir_race Turns off the effect of -ignore_readdir_race. -noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed. -version, --version Print the find version number and exit. -xdev Don't descend directories on other filesystems. TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line. When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed. If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status. A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as +n for greater than n, -n for less than n, n for exactly n. Supported tests: -amin n File was last accessed less than, more than or exactly n minutes ago. -anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -atime n File was last accessed less than, more than or exactly n*24 hours ago. When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago. -cmin n File's status was last changed less than, more than or exactly n minutes ago. -cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -ctime n File's status was last changed less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file status change times. -empty File is empty and is either a regular file or a directory. -executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed. -false Always false. -fstype type File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems. -gid n File's numeric group ID is less than, more than or exactly n. -group gname File belongs to group gname (numeric group ID allowed). -ilname pattern Like -lname, but the match is case insensitive. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -iname pattern Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc. The pattern `*foo*` will also match a file called '.foobar'. -inum n File has inode number smaller than, greater than or exactly n. It is normally easier to use the -samefile test instead. -ipath pattern Like -path. but the match is case insensitive. -iregex pattern Like -regex, but the match is case insensitive. -iwholename pattern See -ipath. This alternative is less portable than -ipath. -links n File has less than, more than or exactly n hard links. -lname pattern File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken. -mmin n File's data was last modified less than, more than or exactly n minutes ago. -mtime n File's data was last modified less than, more than or exactly n*24 hours ago. See the comments for -atime to understand how rounding affects the interpretation of file modification times. -name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern. Because the leading directories of the file names are removed, the pattern should not include a slash, because `-name a/b' will never match anything (and you probably want to use -path instead). An exception to this is when using only a slash as pattern (`-name /'), because that is a valid string for matching the root directory "/" (because the base name of "/" is "/"). A warning is issued if you try to pass a pattern containing a - but not consisting solely of one - slash, unless the environment variable POSIXLY_CORRECT is set or the option -nowarn is used. To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action. Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns. The filename matching is performed with the use of the fnmatch(3) library function. Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell. -newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used. -newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters: a The access time of the file reference B The birth time of the file reference c The inode status change time of reference m The modification time of the file reference t reference is interpreted directly as a time Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date. If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results. If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown. -nogroup No group corresponds to file's numeric group ID. -nouser No user corresponds to file's numeric user ID. -path pattern File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line. It would only make sense to use an absolute path name here if the relevant start point is also an absolute path. This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line). The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard. -perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string. For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set). It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission. See the EXAMPLES section for some illustrative examples. -perm -mode All of the permission bits mode are set for the file. Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. -perm /mode Any of the permission bits mode are set for the file. Symbolic modes are accepted in this form. You must specify `u', `g' or `o' if you use a symbolic mode. See the EXAMPLES section for some illustrative examples. If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000). -perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead. -readable Matches files which are readable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -regex pattern File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'. The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option. -samefile name File refers to the same inode as name. When -L is in effect, this can include symbolic links. -size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up. The following suffixes can be used: `b' for 512-byte blocks (this is the default if no suffix is used) `c' for bytes `w' for two-byte words `k' for kibibytes (KiB, units of 1024 bytes) `M' for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes) `G' for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes) The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above. In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently. The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls. The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match. Bear in mind that the size is rounded up to the next unit. Therefore -size -1M is not equivalent to -size -1048576c. The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes. -true Always true. -type c File is of type c: b block (buffered) special c character (unbuffered) special d directory p named pipe (FIFO) f regular file l symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken. If you want to search for symbolic links when -L is in effect, use -xtype. s socket D door (Solaris) To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension). -uid n File's numeric user ID is less than, more than or exactly n. -used n File was last accessed less than, more than or exactly n days after its status was last changed. -user uname File is owned by user uname (numeric user ID allowed). -wholename pattern See -path. This alternative is less portable than -path. -writable Matches files which are writable by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores. This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root- squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server. -xtype c The same as -type unless the file is a symbolic link. For symbolic links: if the -H or -P option was specified, true if the file is a link to a file of type c; if the -L option has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check. -context pattern (SELinux only) Security context of the file matches glob pattern. ACTIONS -delete Delete files or directories; true if removal succeeded. If the removal failed, an error message is issued and find's exit status will be nonzero (when it eventually exits). Warning: Don't forget that find evaluates the command line as an expression, so putting -delete first will make find try to delete everything below the starting points you specified. The use of the -delete action on the command line automatically turns on the -depth option. As in turn -depth makes -prune ineffective, the -delete action cannot usefully be combined with -prune. Often, the user might want to test a find command line with -print prior to adding -delete for the actual removal run. To avoid surprising results, it is usually best to remember to use -depth explicitly during those earlier test runs. The -delete action will fail to remove a directory unless it is empty. Together with the -ignore_readdir_race option, find will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, not change the exit code to nonzero, and the return code of the -delete action will be true. -exec command ; Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. See the EXAMPLES section for examples of the use of the -exec option. The specified command is run once for each matched file. The command is executed in the starting directory. There are unavoidable security problems surrounding use of the -exec action; you should use the -execdir option instead. -exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command, and it must appear at the end, immediately before the `+'; it needs to be escaped (with a `\') or quoted to protect it from interpretation by the shell. The command is executed in the starting directory. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. For this reason -exec my- command ... {} + -quit may not result in my-command actually being run. This variant of -exec always returns true. -execdir command ; -execdir command {} + Like -exec, but the specified command is run from the subdirectory containing the matched file, which is not normally the directory in which you started find. As with -exec, the {} should be quoted if find is being invoked from a shell. This a much more secure method for invoking commands, as it avoids race conditions during resolution of the paths to the matched files. As with the -exec action, the `+' form of -execdir will build a command line to process more than one matched file, but any given invocation of command will only list files that exist in the same subdirectory. If you use this option, you must ensure that your PATH environment variable does not reference `.'; otherwise, an attacker can run any commands they like by leaving an appropriately-named file in a directory in which you will run -execdir. The same applies to having entries in PATH which are empty or which are not absolute directory names. If any invocation with the `+' form returns a non-zero value as exit status, then find returns a non-zero exit status. If find encounters an error, this can sometimes cause an immediate exit, so some pending commands may not be run at all. The result of the action depends on whether the + or the ; variant is being used; -execdir command {} + always returns true, while -execdir command {} ; returns true only if command returns 0. -fls file True; like -ls but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint file True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names /dev/stdout and /dev/stderr are handled specially; they refer to the standard output and standard error output, respectively. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprint0 file True; like -print0 but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -fprintf file format True; like -printf but write to file like -fprint. The output file is always created, even if the predicate is never matched. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ls True; list current file in ls -dils format on standard output. The block counts are of 1 KB blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -ok command ; Like -exec but ask the user first. If the user agrees, run the command. Otherwise just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. The response to the prompt is matched against a pair of regular expressions to determine if it is an affirmative or negative response. This regular expression is obtained from the system if the POSIXLY_CORRECT environment variable is set, or otherwise from find's message translations. If the system has no suitable definition, find's own definition will be used. In either case, the interpretation of the regular expression itself will be affected by the environment variables LC_CTYPE (character classes) and LC_COLLATE (character ranges and equivalence classes). -okdir command ; Like -execdir but ask the user first in the same way as for -ok. If the user does not agree, just return false. If the command is run, its standard input is redirected from /dev/null. This action may not be specified together with the -files0-from option. -print True; print the full file name on the standard output, followed by a newline. If you are piping the output of find into another program and there is the faintest possibility that the files which you are searching for might contain a newline, then you should seriously consider using the -print0 option instead of -print. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -print0 True; print the full file name on the standard output, followed by a null character (instead of the newline character that -print uses). This allows file names that contain newlines or other types of white space to be correctly interpreted by programs that process the find output. This option corresponds to the -0 option of xargs. -printf format True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the printf(3) C function. Please note that many of the fields are printed as %s rather than %d, and this may mean that flags don't work as you might expect. This also means that the `-' flag does work (it forces fields to be left-aligned). Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are: \a Alarm bell. \b Backspace. \c Stop printing from this format immediately and flush the output. \f Form feed. \n Newline. \r Carriage return. \t Horizontal tab. \v Vertical tab. \0 ASCII NUL. \\ A literal backslash (`\'). \NNN The character whose ASCII code is NNN (octal). A `\' character followed by any other character is treated as an ordinary character, so they both are printed. %% A literal percent sign. %a File's last access time in the format returned by the C ctime(3) function. %Ak File's last access time in the format specified by k, which is either `@' or a directive for the C strftime(3) function. The following shows an incomplete list of possible values for k. Please refer to the documentation of strftime(3) for the full list. Some of the conversion specification characters might not be available on all systems, due to differences in the implementation of the strftime(3) library function. @ seconds since Jan. 1, 1970, 00:00 GMT, with fractional part. Time fields: H hour (00..23) I hour (01..12) k hour ( 0..23) l hour ( 1..12) M minute (00..59) p locale's AM or PM r time, 12-hour (hh:mm:ss [AP]M) S Second (00.00 .. 61.00). There is a fractional part. T time, 24-hour (hh:mm:ss.xxxxxxxxxx) + Date and time, separated by `+', for example `2004-04-28+22:22:05.0'. This is a GNU extension. The time is given in the current timezone (which may be affected by setting the TZ environment variable). The seconds field includes a fractional part. X locale's time representation (H:M:S). The seconds field includes a fractional part. Z time zone (e.g., EDT), or nothing if no time zone is determinable Date fields: a locale's abbreviated weekday name (Sun..Sat) A locale's full weekday name, variable length (Sunday..Saturday) b locale's abbreviated month name (Jan..Dec) B locale's full month name, variable length (January..December) c locale's date and time (Sat Nov 04 12:02:33 EST 1989). The format is the same as for ctime(3) and so to preserve compatibility with that format, there is no fractional part in the seconds field. d day of month (01..31) D date (mm/dd/yy) F date (yyyy-mm-dd) h same as b j day of year (001..366) m month (01..12) U week number of year with Sunday as first day of week (00..53) w day of week (0..6) W week number of year with Monday as first day of week (00..53) x locale's date representation (mm/dd/yy) y last two digits of year (00..99) Y year (1970...) %b The amount of disk space used for this file in 512-byte blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/512, but it can also be smaller if the file is a sparse file. %Bk File's birth time, i.e., its creation time, in the format specified by k, which is the same as for %A. This directive produces an empty string if the underlying operating system or filesystem does not support birth times. %c File's last status change time in the format returned by the C ctime(3) function. %Ck File's last status change time in the format specified by k, which is the same as for %A. %d File's depth in the directory tree; 0 means the file is a starting-point. %D The device number on which the file exists (the st_dev field of struct stat), in decimal. %f Print the basename; the file's name with any leading directories removed (only the last element). For /, the result is `/'. See the EXAMPLES section for an example. %F Type of the filesystem the file is on; this value can be used for -fstype. %g File's group name, or numeric group ID if the group has no name. %G File's numeric group ID. %h Dirname; the Leading directories of the file's name (all but the last element). If the file name contains no slashes (since it is in the current directory) the %h specifier expands to `.'. For files which are themselves directories and contain a slash (including /), %h expands to the empty string. See the EXAMPLES section for an example. %H Starting-point under which file was found. %i File's inode number (in decimal). %k The amount of disk space used for this file in 1 KB blocks. Since disk space is allocated in multiples of the filesystem block size this is usually greater than %s/1024, but it can also be smaller if the file is a sparse file. %l Object of symbolic link (empty string if file is not a symbolic link). %m File's permission bits (in octal). This option uses the `traditional' numbers which most Unix implementations use, but if your particular implementation uses an unusual ordering of octal permissions bits, you will see a difference between the actual value of the file's mode and the output of %m. Normally you will want to have a leading zero on this number, and to do this, you should use the # flag (as in, for example, `%#m'). %M File's permissions (in symbolic form, as for ls). This directive is supported in findutils 4.2.5 and later. %n Number of hard links to file. %p File's name. %P File's name with the name of the starting-point under which it was found removed. %s File's size in bytes. %S File's sparseness. This is calculated as (BLOCKSIZE*st_blocks / st_size). The exact value you will get for an ordinary file of a certain length is system-dependent. However, normally sparse files will have values less than 1.0, and files which use indirect blocks may have a value which is greater than 1.0. In general the number of blocks used by a file is file system dependent. The value used for BLOCKSIZE is system-dependent, but is usually 512 bytes. If the file size is zero, the value printed is undefined. On systems which lack support for st_blocks, a file's sparseness is assumed to be 1.0. %t File's last modification time in the format returned by the C ctime(3) function. %Tk File's last modification time in the format specified by k, which is the same as for %A. %u File's user name, or numeric user ID if the user has no name. %U File's numeric user ID. %y File's type (like in ls -l), U=unknown type (shouldn't happen) %Y File's type (like %y), plus follow symbolic links: `L'=loop, `N'=nonexistent, `?' for any other error when determining the type of the target of a symbolic link. %Z (SELinux only) file's security context. %{ %[ %( Reserved for future use. A `%' character followed by any other character is discarded, but the other character is printed (don't rely on this, as further format characters may be introduced). A `%' at the end of the format argument causes undefined behaviour since there is no following character. In some locales, it may hide your door keys, while in others it may remove the final page from the novel you are reading. The %m and %d directives support the #, 0 and + flags, but the other directives do not, even if they print numbers. Numeric directives that do not support these flags include G, U, b, D, k and n. The `-' format flag is supported and changes the alignment of a field from right-justified (which is the default) to left-justified. See the UNUSUAL FILENAMES section for information about how unusual characters in filenames are handled. -prune True; if the file is a directory, do not descend into it. If -depth is given, then -prune has no effect. Because -delete implies -depth, you cannot usefully use -prune and -delete together. For example, to skip the directory src/emacs and all files and directories under it, and print the names of the other files found, do something like this: find . -path ./src/emacs -prune -o -print -quit Exit immediately (with return value zero if no errors have occurred). This is different to -prune because -prune only applies to the contents of pruned directories, while -quit simply makes find stop immediately. No child processes will be left running. Any command lines which have been built by -exec ... + or -execdir ... + are invoked before the program is exited. After -quit is executed, no more files specified on the command line will be processed. For example, `find /tmp/foo /tmp/bar -print -quit` will print only `/tmp/foo`. One common use of -quit is to stop searching the file system once we have found what we want. For example, if we want to find just a single file we can do this: find / -name needle -print -quit OPERATORS Listed in order of decreasing precedence: ( expr ) Force precedence. Since parentheses are special to the shell, you will normally need to quote them. Many of the examples in this manual page use backslashes for this purpose: `\(...\)' instead of `(...)'. ! expr True if expr is false. This character will also usually need protection from interpretation by the shell. -not expr Same as ! expr, but not POSIX compliant. expr1 expr2 Two expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is false. expr1 -a expr2 Same as expr1 expr2. expr1 -and expr2 Same as expr1 expr2, but not POSIX compliant. expr1 -o expr2 Or; expr2 is not evaluated if expr1 is true. expr1 -or expr2 Same as expr1 -o expr2, but not POSIX compliant. expr1 , expr2 List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2. The comma operator can be useful for searching for several different types of thing, but traversing the filesystem hierarchy only once. The -fprintf action can be used to list the various matched items into several different output files. Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator between them) or explicitly has higher precedence than -o. This means that find . -name afile -o -name bfile -print will never print afile. UNUSUAL FILENAMES top Many of the actions of find result in the printing of data which is under the control of other users. This includes file names, sizes, modification times and so forth. File names are a potential problem since they can contain any character except `\0' and `/'. Unusual characters in file names can do unexpected and often undesirable things to your terminal (for example, changing the settings of your function keys on some terminals). Unusual characters are handled differently by various actions, as described below. -print0, -fprint0 Always print the exact filename, unchanged, even if the output is going to a terminal. -ls, -fls Unusual characters are always escaped. White space, backslash, and double quote characters are printed using C-style escaping (for example `\f', `\"'). Other unusual characters are printed using an octal escape. Other printable characters (for -ls and -fls these are the characters between octal 041 and 0176) are printed as-is. -printf, -fprintf If the output is not going to a terminal, it is printed as-is. Otherwise, the result depends on which directive is in use. The directives %D, %F, %g, %G, %H, %Y, and %y expand to values which are not under control of files' owners, and so are printed as-is. The directives %a, %b, %c, %d, %i, %k, %m, %M, %n, %s, %t, %u and %U have values which are under the control of files' owners but which cannot be used to send arbitrary data to the terminal, and so these are printed as-is. The directives %f, %h, %l, %p and %P are quoted. This quoting is performed in the same way as for GNU ls. This is not the same quoting mechanism as the one used for -ls and -fls. If you are able to decide what format to use for the output of find then it is normally better to use `\0' as a terminator than to use newline, as file names can contain white space and newline characters. The setting of the LC_CTYPE environment variable is used to determine which characters need to be quoted. -print, -fprint Quoting is handled in the same way as for -printf and -fprintf. If you are using find in a script or in a situation where the matched files might have arbitrary names, you should consider using -print0 instead of -print. The -ok and -okdir actions print the current filename as-is. This may change in a future release. STANDARDS CONFORMANCE top For closest compliance to the POSIX standard, you should set the POSIXLY_CORRECT environment variable. The following options are specified in the POSIX standard (IEEE Std 1003.1-2008, 2016 Edition): -H This option is supported. -L This option is supported. -name This option is supported, but POSIX conformance depends on the POSIX conformance of the system's fnmatch(3) library function. As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) match a leading `.', because IEEE PASC interpretation 126 requires this. This is a change from previous versions of findutils. -type Supported. POSIX specifies `b', `c', `d', `l', `p', `f' and `s'. GNU find also supports `D', representing a Door, where the OS provides these. Furthermore, GNU find allows multiple types to be specified at once in a comma- separated list. -ok Supported. Interpretation of the response is according to the `yes' and `no' patterns selected by setting the LC_MESSAGES environment variable. When the POSIXLY_CORRECT environment variable is set, these patterns are taken system's definition of a positive (yes) or negative (no) response. See the system's documentation for nl_langinfo(3), in particular YESEXPR and NOEXPR. When POSIXLY_CORRECT is not set, the patterns are instead taken from find's own message catalogue. -newer Supported. If the file specified is a symbolic link, it is always dereferenced. This is a change from previous behaviour, which used to take the relevant time from the symbolic link; see the HISTORY section below. -perm Supported. If the POSIXLY_CORRECT environment variable is not set, some mode arguments (for example +a+x) which are not valid in POSIX are supported for backward- compatibility. Other primaries The primaries -atime, -ctime, -depth, -exec, -group, -links, -mtime, -nogroup, -nouser, -ok, -path, -print, -prune, -size, -user and -xdev are all supported. The POSIX standard specifies parentheses `(', `)', negation `!' and the logical AND/OR operators -a and -o. All other options, predicates, expressions and so forth are extensions beyond the POSIX standard. Many of these extensions are not unique to GNU find, however. The POSIX standard requires that find detects loops: The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate. GNU find complies with these requirements. The link count of directories which contain entries which are hard links to an ancestor will often be lower than they otherwise should be. This can mean that GNU find will sometimes optimise away the visiting of a subdirectory which is actually a link to an ancestor. Since find does not actually enter such a subdirectory, it is allowed to avoid emitting a diagnostic message. Although this behaviour may be somewhat confusing, it is unlikely that anybody actually depends on this behaviour. If the leaf optimisation has been turned off with -noleaf, the directory entry will always be examined and the diagnostic message will be issued where it is appropriate. Symbolic links cannot be used to create filesystem cycles as such, but if the -L option or the -follow option is in use, a diagnostic message is issued when find encounters a loop of symbolic links. As with loops containing hard links, the leaf optimisation will often mean that find knows that it doesn't need to call stat() or chdir() on the symbolic link, so this diagnostic is frequently not necessary. The -d option is supported for compatibility with various BSD systems, but you should use the POSIX-compliant option -depth instead. The POSIXLY_CORRECT environment variable does not affect the behaviour of the -regex or -iregex tests because those tests aren't specified in the POSIX standard. ENVIRONMENT VARIABLES top LANG Provides a default value for the internationalization variables that are unset or null. LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_COLLATE The POSIX standard specifies that this variable affects the pattern matching to be used for the -name option. GNU find uses the fnmatch(3) library function, and so support for LC_COLLATE depends on the system library. This variable also affects the interpretation of the response to -ok; while the LC_MESSAGES variable selects the actual pattern used to interpret the response to -ok, the interpretation of any bracket expressions in the pattern will be affected by LC_COLLATE. LC_CTYPE This variable affects the treatment of character classes used in regular expressions and also with the -name test, if the system's fnmatch(3) library function supports this. This variable also affects the interpretation of any character classes in the regular expressions used to interpret the response to the prompt issued by -ok. The LC_CTYPE environment variable will also affect which characters are considered to be unprintable when filenames are printed; see the section UNUSUAL FILENAMES. LC_MESSAGES Determines the locale to be used for internationalised messages. If the POSIXLY_CORRECT environment variable is set, this also determines the interpretation of the response to the prompt made by the -ok action. NLSPATH Determines the location of the internationalisation message catalogues. PATH Affects the directories which are searched to find the executables invoked by -exec, -execdir, -ok and -okdir. POSIXLY_CORRECT Determines the block size used by -ls and -fls. If POSIXLY_CORRECT is set, blocks are units of 512 bytes. Otherwise they are units of 1024 bytes. Setting this variable also turns off warning messages (that is, implies -nowarn) by default, because POSIX requires that apart from the output for -ok, all messages printed on stderr are diagnostics and must result in a non-zero exit status. When POSIXLY_CORRECT is not set, -perm +zzz is treated just like -perm /zzz if +zzz is not a valid symbolic mode. When POSIXLY_CORRECT is set, such constructs are treated as an error. When POSIXLY_CORRECT is set, the response to the prompt made by the -ok action is interpreted according to the system's message catalogue, as opposed to according to find's own message translations. TZ Affects the time zone used for some of the time-related format directives of -printf and -fprintf. EXAMPLES top Simple `find|xargs` approach Find files named core in or below the directory /tmp and delete them. $ find /tmp -name core -type f -print | xargs /bin/rm -f Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces. Safer `find -print0 | xargs -0` approach Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. $ find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f The -name test comes before the -type test in order to avoid having to call stat(2) on every file. Note that there is still a race between the time find traverses the hierarchy printing the matching filenames, and the time the process executed by xargs works with that file. Processing arbitrary starting points Given that another program proggy pre-filters and creates a huge NUL-separated list of files, process those as starting points, and find all regular, empty files among them: $ proggy | find -files0-from - -maxdepth 0 -type f -empty The use of `-files0-from -` means to read the names of the starting points from standard input, i.e., from the pipe; and -maxdepth 0 ensures that only explicitly those entries are examined without recursing into directories (in the case one of the starting points is one). Executing a command for each file Run file on every file in or below the current directory. $ find . -type f -exec file '{}' \; Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though single quotes could have been used in that case also. In many cases, one might prefer the `-exec ... +` or better the `-execdir ... +` syntax for performance and security reasons. Traversing the filesystem just once - for 2 different actions Traverse the filesystem just once, listing set-user-ID files and directories into /root/suid.txt and large files into /root/big.txt. $ find / \ \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \ \( -size +100M -fprintf /root/big.txt '%-10s %p\n' \) This example uses the line-continuation character '\' on the first two lines to instruct the shell to continue reading the command on the next line. Searching files by age Search for files in your home directory which have been modified in the last twenty-four hours. $ find $HOME -mtime 0 This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime 0, a file will have to have a modification in the past which is less than 24 hours ago. Searching files by permissions Search for files which are executable but not readable. $ find /sbin /usr/sbin -executable \! -readable -print Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. $ find . -perm 664 Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched. Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). $ find . -perm -664 This will match a file which has mode 0777, for example. Search for files which are writable by somebody (their owner, or their group, or anybody else). $ find . -perm /222 Search for files which are writable by either their owner or their group. $ find . -perm /220 $ find . -perm /u+w,g+w $ find . -perm /u=w,g=w All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. The files don't have to be writable by both the owner and group to be matched; either will do. Search for files which are writable by both their owner and their group. $ find . -perm -220 $ find . -perm -g+w,u+w Both these commands do the same thing. A more elaborate search on permissions. $ find . -perm -444 -perm /222 \! -perm /111 $ find . -perm -a+r -perm /a+w \! -perm /a+x These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least one write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 or ! -perm /a+x respectively). Pruning - omitting files and subdirectories Copy the contents of /source-dir to /dest-dir, but omit files and directories named .snapshot (and anything in them). It also omits files or directories whose name ends in `~', but not their contents. $ cd /source-dir $ find . -name .snapshot -prune -o \( \! -name '*~' -print0 \) \ | cpio -pmd0 /dest-dir The construct -prune -o \( ... -print0 \) is quite common. The idea here is that the expression before -prune matches things which are to be pruned. However, the -prune action itself returns true, so the following -o ensures that the right hand side is evaluated only for those directories which didn't get pruned (the contents of the pruned directories are not even visited, so their contents are irrelevant). The expression on the right hand side of the -o is in parentheses only for clarity. It emphasises that the -print0 action takes place only for things that didn't have -prune applied to them. Because the default `and' condition between tests binds more tightly than -o, this is the default anyway, but the parentheses help to show what is going on. Given the following directory of projects and their associated SCM administrative directories, perform an efficient search for the projects' roots: $ find repo/ \ \( -exec test -d '{}/.svn' \; \ -or -exec test -d '{}/.git' \; \ -or -exec test -d '{}/CVS' \; \ \) -print -prune Sample output: repo/project1/CVS repo/gnu/project2/.svn repo/gnu/project3/.svn repo/gnu/project3/src/.svn repo/project4/.git In this example, -prune prevents unnecessary descent into directories that have already been discovered (for example we do not search project3/src because we already found project3/.svn), but ensures sibling directories (project2 and project3) are found. Other useful examples Search for several file types. $ find /tmp -type f,d,l Search for files, directories, and symbolic links in the directory /tmp passing these types as a comma-separated list (GNU extension), which is otherwise equivalent to the longer, yet more portable: $ find /tmp \( -type f -o -type d -o -type l \) Search for files with the particular name needle and stop immediately when we find the first one. $ find / -name needle -print -quit Demonstrate the interpretation of the %f and %h format directives of the -printf action for some corner-cases. Here is an example including some output. $ find . .. / /tmp /tmp/TRACE compile compile/64/tests/find -maxdepth 0 -printf '[%h][%f]\n' [.][.] [.][..] [][/] [][tmp] [/tmp][TRACE] [.][compile] [compile/64/tests][find] EXIT STATUS top find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find. When some error occurs, find may stop immediately, without completing all the actions specified. For example, some starting points may not have been examined or some pending program invocations for -exec ... {} + or -execdir ... {} + may not have been performed. HISTORY top A find program appeared in Version 5 Unix as part of the Programmer's Workbench project and was written by Dick Haight. Doug McIlroy's A Research UNIX Reader: Annotated Excerpts from the Programmers Manual, 1971-1986 provides some additional details; you can read it on-line at <https://www.cs.dartmouth.edu/~doug/reader.pdf>. GNU find was originally written by Eric Decker, with enhancements by David MacKenzie, Jay Plett, and Tim Wood. The idea for find -print0 and xargs -0 came from Dan Bernstein. COMPATIBILITY top As of findutils-4.2.2, shell metacharacters (`*', `?' or `[]' for example) used in filename patterns match a leading `.', because IEEE POSIX interpretation 126 requires this. As of findutils-4.3.3, -perm /000 now matches all files instead of none. Nanosecond-resolution timestamps were implemented in findutils-4.3.3. As of findutils-4.3.11, the -delete action sets find's exit status to a nonzero value when it fails. However, find will not exit immediately. Previously, find's exit status was unaffected by the failure of -delete. Feature Added in Also occurs in -files0-from 4.9.0 -newerXY 4.3.3 BSD -D 4.3.1 -O 4.3.1 -readable 4.3.0 -writable 4.3.0 -executable 4.3.0 -regextype 4.2.24 -exec ... + 4.2.12 POSIX -execdir 4.2.12 BSD -okdir 4.2.12 -samefile 4.2.11 -H 4.2.5 POSIX -L 4.2.5 POSIX -P 4.2.5 BSD -delete 4.2.3 -quit 4.2.3 -d 4.2.3 BSD -wholename 4.2.0 -iwholename 4.2.0 -ignore_readdir_race 4.2.0 -fls 4.0 -ilname 3.8 -iname 3.8 -ipath 3.8 -iregex 3.8 The syntax -perm +MODE was removed in findutils-4.5.12, in favour of -perm /MODE. The +MODE syntax had been deprecated since findutils-4.2.21 which was released in 2005. NON-BUGS top Operator precedence surprises The command find . -name afile -o -name bfile -print will never print afile because this is actually equivalent to find . -name afile -o \( -name bfile -a -print \). Remember that the precedence of -a is higher than that of -o and when there is no operator specified between tests, -a is assumed. paths must precede expression error message $ find . -name *.c -print find: paths must precede expression find: possible unquoted pattern after predicate `-name'? This happens when the shell could expand the pattern *.c to more than one file name existing in the current directory, and passing the resulting file names in the command line to find like this: find . -name frcode.c locate.c word_io.c -print That command is of course not going to work, because the -name predicate allows exactly only one pattern as argument. Instead of doing things this way, you should enclose the pattern in quotes or escape the wildcard, thus allowing find to use the pattern with the wildcard during the search for file name matching instead of file names expanded by the parent shell: $ find . -name '*.c' -print $ find . -name \*.c -print BUGS top There are security problems inherent in the behaviour that the POSIX standard specifies for find, which therefore cannot be fixed. For example, the -exec action is inherently insecure, and -execdir should be used instead. The environment variable LC_COLLATE has no effect on the -ok action. REPORTING BUGS top GNU findutils online help: <https://www.gnu.org/software/findutils/#get-help> Report any translation bugs to <https://translationproject.org/team/> Report any other issue via the form at the GNU Savannah bug tracker: <https://savannah.gnu.org/bugs/?group=findutils> General topics about the GNU findutils package are discussed at the bug-findutils mailing list: <https://lists.gnu.org/mailman/listinfo/bug-findutils> COPYRIGHT top Copyright 1990-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top chmod(1), locate(1), ls(1), updatedb(1), xargs(1), lstat(2), stat(2), ctime(3) fnmatch(3), printf(3), strftime(3), locatedb(5), regex(7) Full documentation <https://www.gnu.org/software/findutils/find> or available locally via: info find COLOPHON top This page is part of the findutils (find utilities) project. Information about the project can be found at http://www.gnu.org/software/findutils/. If you have a bug report for this manual page, see https://savannah.gnu.org/bugs/?group=findutils. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/findutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-11-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org FIND(1) Pages that refer to this page: dpkg(1), dpkg-name(1), find-filter(1), grep(1), ippfind(1), locate(1), mkaf(1), pmlogger_daily(1), tar(1), updatedb(1), xargs(1), fts(3), proc(5), hier(7), symlink(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. diff(1) - Linux manual page man7.org > Linux > man-pages Linux/UNIX system programming training diff(1) Linux manual page NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON DIFF(1) User Commands DIFF(1) NAME top diff - compare files line by line SYNOPSIS top diff [OPTION]... FILES DESCRIPTION top Compare FILES line by line. Mandatory arguments to long options are mandatory for short options too. --normal output a normal diff (the default) -q, --brief report only when files differ -s, --report-identical-files report when two files are the same -c, -C NUM, --context[=NUM] output NUM (default 3) lines of copied context -u, -U NUM, --unified[=NUM] output NUM (default 3) lines of unified context -e, --ed output an ed script -n, --rcs output an RCS format diff -y, --side-by-side output in two columns -W, --width=NUM output at most NUM (default 130) print columns --left-column output only the left column of common lines --suppress-common-lines do not output common lines -p, --show-c-function show which C function each change is in -F, --show-function-line=RE show the most recent line matching RE --label LABEL use LABEL instead of file name and timestamp (can be repeated) -t, --expand-tabs expand tabs to spaces in output -T, --initial-tab make tabs line up by prepending a tab --tabsize=NUM tab stops every NUM (default 8) print columns --suppress-blank-empty suppress space or tab before empty output lines -l, --paginate pass output through 'pr' to paginate it -r, --recursive recursively compare any subdirectories found --no-dereference don't follow symbolic links -N, --new-file treat absent files as empty --unidirectional-new-file treat absent first files as empty --ignore-file-name-case ignore case when comparing file names --no-ignore-file-name-case consider case when comparing file names -x, --exclude=PAT exclude files that match PAT -X, --exclude-from=FILE exclude files that match any pattern in FILE -S, --starting-file=FILE start with FILE when comparing directories --from-file=FILE1 compare FILE1 to all operands; FILE1 can be a directory --to-file=FILE2 compare all operands to FILE2; FILE2 can be a directory -i, --ignore-case ignore case differences in file contents -E, --ignore-tab-expansion ignore changes due to tab expansion -Z, --ignore-trailing-space ignore white space at line end -b, --ignore-space-change ignore changes in the amount of white space -w, --ignore-all-space ignore all white space -B, --ignore-blank-lines ignore changes where lines are all blank -I, --ignore-matching-lines=RE ignore changes where all lines match RE -a, --text treat all files as text --strip-trailing-cr strip trailing carriage return on input -D, --ifdef=NAME output merged file with '#ifdef NAME' diffs --GTYPE-group-format=GFMT format GTYPE input groups with GFMT --line-format=LFMT format all input lines with LFMT --LTYPE-line-format=LFMT format LTYPE input lines with LFMT These format options provide fine-grained control over the output of diff, generalizing -D/--ifdef. LTYPE is 'old', 'new', or 'unchanged'. GTYPE is LTYPE or 'changed'. GFMT (only) may contain: %< lines from FILE1 %> lines from FILE2 %= lines common to FILE1 and FILE2 %[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER LETTERs are as follows for new group, lower case for old group: F first line number L last line number N number of lines = L-F+1 E F-1 M L+1 %(A=B?T:E) if A equals B then T else E LFMT (only) may contain: %L contents of line %l contents of line, excluding any trailing newline %[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number Both GFMT and LFMT may contain: %% % %c'C' the single character C %c'\OOO' the character with octal code OOO C the character C (other characters represent themselves) -d, --minimal try hard to find a smaller set of changes --horizon-lines=NUM keep NUM lines of the common prefix and suffix --speed-large-files assume large files and many scattered small changes --color[=WHEN] color output; WHEN is 'never', 'always', or 'auto'; plain --color means --color='auto' --palette=PALETTE the colors to use when --color is active; PALETTE is a colon-separated list of terminfo capabilities --help display this help and exit -v, --version output version information and exit FILES are 'FILE1 FILE2' or 'DIR1 DIR2' or 'DIR FILE' or 'FILE DIR'. If --from-file or --to-file is given, there are no restrictions on FILE(s). If a FILE is '-', read standard input. Exit status is 0 if inputs are the same, 1 if different, 2 if trouble. AUTHOR top Written by Paul Eggert, Mike Haertel, David Hayes, Richard Stallman, and Len Tower. REPORTING BUGS top Report bugs to: bug-diffutils@gnu.org GNU diffutils home page: <https://www.gnu.org/software/diffutils/> General help using GNU software: <https://www.gnu.org/gethelp/> COPYRIGHT top Copyright 2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO top wdiff(1), cmp(1), diff3(1), sdiff(1), patch(1) The full documentation for diff is maintained as a Texinfo manual. If the info and diff programs are properly installed at your site, the command info diff should give you access to the complete manual. COLOPHON top This page is part of the diffutils (GNU diff utilities) project. Information about the project can be found at http://savannah.gnu.org/projects/diffutils/. If you have a bug report for this manual page, send it to bug-diffutils@gnu.org. This page was obtained from the project's upstream Git repository git://git.savannah.gnu.org/diffutils.git on 2023-12-22. (At that time, the date of the most recent commit that was found in the repository was 2023-09-20.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org diffutils 3.10.207-774b December 2023 DIFF(1) Pages that refer to this page: cmp(1), diff3(1), gendiff(1), grep(1), patch(1), quilt(1), sdiff(1), suffixes(7) HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. Task: Compare each .xml file under the current directory with a file of the same name in "/destination/dir/2" Bash Command:<START>find . -name *.xml -exec diff {} /destination/dir/2/{} \;<END>