neulab/tldr huggingface dataset:
MTR_OPTIONS This environment variable allows one to specify options, as if they were passed on the command line.  It is parsed before reading the actual command line options, so that options specified in MTR_OPTIONS are overridden by command-line options.
MTR_OPTIONS="-4 -c 1" mtr -6 localhost
would send one probe (because of -c 1) towards ::1 (because of -6, which overrides the -4 passed in MTR_OPTIONS).
MTR_PACKET A path to the mtr-packet executable, to be used for sending and receiving network probes.  If MTR_PACKET is unset, the PATH will be used to search for an mtr-packet executable.
DISPLAY Specifies an X11 server for the GTK+ frontend.
mtr can be controlled while it is running with the following keys: ?|h     help p       pause (SPACE to resume) d       switching display mode e       toggle MPLS information on/off n       toggle DNS on/off r       reset all counters o str   set the columns to display, default str='LRS N BAWV' j       toggle latency(LS NABWV)/jitter(DR AGJMXI) stats c <n>   report cycle n, default n=infinite i <n>   set the ping interval to n seconds, default n=1 f <n>   set the initial time-to-live(ttl), default n=1 m <n>   set the max time-to-live, default n= # of hops s <n>   set the packet size to n or random(n<0) b <c>   set ping bit pattern to c(0..255) or random(c<0) Q <t>   set ping packet's TOS to t u       switch between ICMP ECHO and UDP datagrams y       switching IP info z       toggle ASN info on/off q       exit
Some modern routers give a lower priority to ICMP ECHO packets than to other network traffic.  Consequently, the reliability of these routers reported by mtr will be significantly lower than the actual reliability of these routers.
For the latest version, see the mtr web page at ⟨http://www.bitwizard.nl/ mtr/⟩
For patches, bug reports, or feature requests, please open an issue on GitHub at: ⟨https://github.com/traviscross/mtr⟩.
mtr-packet(8), traceroute(8), ping(8), socket(7), TCP/IP Illustrated (Stevens, ISBN 0201633469).
PO4A-UPDATEPO(1)       User Contributed Perl Documentation      PO4A-UPDATEPO(1)
po4a-updatepo - update the translation (in PO format) of documentation
po4a-updatepo -f fmt (-m master.docE)+ (-p XX.po)+
(XX.po are the outputs, all others are inputs)
The po4a-updatepo script is in charge of updating PO files to make them reflect the changes made to the original documentation file. For that, it converts the documentation file to a POT file, and call msgmerge(1) on this new POT and on the provided PO files.
It is possible to give more than one PO file (if you want to update several languages at once), and several documentation files (if you want to store the translations of several documents in the same PO file).
If the master document has non-ASCII characters, it will convert the PO files to UTF-8 (if they weren't already), in order to allow non-standard characters in a culture independent way.
-m, --master File(s) containing the master document to translate.
-M, --master-charset Charset of the files containing the document to translate. Note that all files must have the same charset.
-p, --po PO file(s) to update. If these files do not exist, they are created by po4a-updatepo.
-o, --option Extra option(s) to pass to the format plugin and other po4a internal module.  Specify each option in the 'name=value' format. See the documentation of each plugin for more information about the valid options and their meanings.
--msgmerge-opt options Extra options for msgmerge.
po4a-gettextize(1), po4a-normalize(1), po4a-translate(1), po4a(7)
gh-gist - Manage gists
gh gist <command> [flags]
Work with GitHub gists.
gh(1), gh-gist-clone(1), gh-gist-create(1), gh-gist-delete(1), gh-gist- edit(1), gh-gist-list(1), gh-gist-view(1)
HOSTNAMECTL(1)                     hostnamectl                    HOSTNAMECTL(1)
hostnamectl - Control the system hostname
hostnamectl [OPTIONS...] {COMMAND}
hostnamectl may be used to query and change the system hostname and related settings.
systemd-hostnamed.service(8) and this tool distinguish three different hostnames: the high-level "pretty" hostname which might include all kinds of special characters (e.g. "Lennart's Laptop"), the "static" hostname which is the user-configured hostname (e.g. "lennarts-laptop"), and the transient hostname which is a fallback value received from network configuration (e.g. "node12345678"). If a static hostname is set to a valid value, then the transient hostname is not used.
Note that the pretty hostname has little restrictions on the characters and length used, while the static and transient hostnames are limited to the usually accepted characters of Internet domain names, and 64 characters at maximum (the latter being a Linux limitation).
Use systemd-firstboot(1) to initialize the system hostname for mounted (but not booted) system images.
status Show system hostname and related information. If no command is specified, this is the implied default.
hostname [NAME] If no argument is given, print the system hostname. If an optional argument NAME is provided then the command changes the system hostname to NAME. By default, this will alter the pretty, the static, and the transient hostname alike; however, if one or more of --static, --transient, --pretty are used, only the selected hostnames are changed. If the pretty hostname is being set, and static or transient are being set as well, the specified hostname will be simplified in regards to the character set used before the latter are updated. This is done by removing special characters and spaces. This ensures that the pretty and the static hostname are always closely related while still following the validity rules of the specific name. This simplification of the hostname string is not done if only the transient and/or static hostnames are set, and the pretty hostname is left untouched.
The static and transient hostnames must each be either a single DNS label (a string composed of 7-bit ASCII lower-case characters and no spaces or dots, limited to the format allowed for DNS domain name labels), or a sequence of such labels separated by single dots that forms a valid DNS FQDN. The hostname must be at most 64 characters, which is a Linux limitation (DNS allows longer names).
icon-name [NAME] If no argument is given, print the icon name of the system. If an optional argument NAME is provided then the command changes the icon name to NAME. The icon name is used by some graphical applications to visualize this host. The icon name should follow the Icon Naming Specification[1].
chassis [TYPE] If no argument is given, print the chassis type. If an optional argument TYPE is provided then the command changes the chassis type to TYPE. The chassis type is used by some graphical applications to visualize the host or alter user interaction. Currently, the following chassis types are defined: "desktop", "laptop", "convertible", "server", "tablet", "handset", "watch", "embedded", as well as the special chassis types "vm" and "container" for virtualized systems that lack an immediate physical chassis.
deployment [ENVIRONMENT] If no argument is given, print the deployment environment. If an optional argument ENVIRONMENT is provided then the command changes the deployment environment to ENVIRONMENT. Argument ENVIRONMENT must be a single word without any control characters. One of the following is suggested: "development", "integration", "staging", "production".
location [LOCATION] If no argument is given, print the location string for the system. If an optional argument LOCATION is provided then the command changes the location string for the system to LOCATION. Argument LOCATION should be a human-friendly, free-form string describing the physical location of the system, if it is known and applicable. This may be as generic as "Berlin, Germany" or as specific as "Left Rack, 2nd Shelf".
--static, --transient, --pretty If status is invoked (or no explicit command is given) and one of these switches is specified, hostnamectl will print out just this selected hostname.
If used with set-hostname, only the selected hostname(s) will be updated. When more than one of these switches are specified, all the specified hostnames will be updated.
--json=MODE Shows output formatted as JSON. Expects one of "short" (for the shortest possible output without any redundant whitespace or line breaks), "pretty" (for a pretty version of the same, with indentation and line breaks) or "off" (to turn off JSON output, the default).
systemd(1), hostname(1), hostname(5), machine-info(5), systemctl(1), systemd-hostnamed.service(8), systemd-firstboot(1)
1. Icon Naming Specification http://standards.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html
LRUNZIP.1(1)           User Contributed Perl Documentation          LRUNZIP.1(1)
lrunzip - Uncompress LRZ files
lrunzip [options] FILE [... FILE]
lrunzip is identical to "lrzip -d" used to decompress files.
lrzip.conf(5), lrzip(1), lrzcat(1), lrztar(1), lrzuntar(1), lrz(1), bzip2(1), gzip(1), lzop(1), rzip(1), zip(1)
APKTOOL(1)                        User Commands                       APKTOOL(1)
apktool - tool for reverse engineering Android apk files
usage: apktool
-advance,--advanced prints advance information.
-version,--version prints the version then exits
usage: apktool if|install-framework [options] <framework.apk>
-p,--frame-path <dir> Stores framework files into <dir>.
-t,--tag <tag> Tag frameworks using <tag>.
usage: apktool d[ecode] [options] <file_apk>
-f,--force Force delete destination directory.
-o,--output <dir> The name of folder that gets written. Default is apk.out
-p,--frame-path <dir> Uses framework files located in <dir>.
-r,--no-res Do not decode resources.
-s,--no-src Do not decode sources.
-t,--frame-tag <tag> Uses framework files tagged by <tag>.
usage: apktool b[uild] [options] <app_path>
-f,--force-all Skip changes detection and build all files.
-o,--output <dir> The name of apk that gets written. Default is dist/name.apk
For additional info, see: http://ibotpeaches.github.io/Apktool/ For smali/baksmali info, see: http://code.google.com/p/smali/
STRACE(1)                    General Commands Manual                   STRACE(1)
strace - trace system calls and signals
strace [-ACdffhikqqrtttTvVwxxyyzZ] [-I n] [-b execve] [-e expr]... [-O overhead] [-S sortby] [-U columns] [-a column] [-o file] [-s strsize] [-X format] [-P path]... [-p pid]... [--seccomp-bpf] { -p pid | [-DDD] [-E var[=val]]... [-u username] command [args] }
strace -c [-dfwzZ] [-I n] [-b execve] [-e expr]... [-O overhead] [-S sortby] [-U columns] [-P path]... [-p pid]... [--seccomp-bpf] { -p pid | [-DDD] [-E var[=val]]... [-u username] command [args] }
In the simplest case strace runs the specified command until it exits. It intercepts and records the system calls which are called by a process and the signals which are received by a process.  The name of each system call, its arguments and its return value are printed on standard error or to the file specified with the -o option.
strace is a useful diagnostic, instructional, and debugging tool.  System administrators, diagnosticians and trouble-shooters will find it invaluable for solving problems with programs for which the source is not readily available since they do not need to be recompiled in order to trace them.  Students, hackers and the overly-curious will find that a great deal can be learned about a system and its system calls by tracing even ordinary programs.  And programmers will find that since system calls and signals are events that happen at the user/kernel interface, a close examination of this boundary is very useful for bug isolation, sanity checking and attempting to capture race conditions.
Each line in the trace contains the system call name, followed by its arguments in parentheses and its return value.  An example from stracing the command "cat /dev/null" is:
open("/dev/null", O_RDONLY) = 3
Errors (typically a return value of -1) have the errno symbol and error string appended.
open("/foo/bar", O_RDONLY) = -1 ENOENT (No such file or directory)
Signals are printed as signal symbol and decoded siginfo structure.  An excerpt from stracing and interrupting the command "sleep 666" is:
sigsuspend([] <unfinished ...> --- SIGINT {si_signo=SIGINT, si_code=SI_USER, si_pid=...} --- +++ killed by SIGINT +++
If a system call is being executed and meanwhile another one is being called from a different thread/process then strace will try to preserve the order of those events and mark the ongoing call as being unfinished. When the call returns it will be marked as resumed.
[pid 28772] select(4, [3], NULL, NULL, NULL <unfinished ...> [pid 28779] clock_gettime(CLOCK_REALTIME, {1130322148, 939977000}) = 0 [pid 28772] <... select resumed> )      = 1 (in [3])
Interruption of a (restartable) system call by a signal delivery is processed differently as kernel terminates the system call and also arranges its immediate reexecution after the signal handler completes.
read(0, 0x7ffff72cf5cf, 1)              = ? ERESTARTSYS (To be restarted) --- SIGALRM ... --- rt_sigreturn(0xe)                       = 0 read(0, "", 1)                          = 0
Arguments are printed in symbolic form with passion.  This example shows the shell performing ">>xyzzy" output redirection:
open("xyzzy", O_WRONLY|O_APPEND|O_CREAT, 0666) = 3
Here, the second and the third argument of open(2) are decoded by breaking down the flag argument into its three bitwise-OR constituents and printing the mode value in octal by tradition.  Where the traditional or native usage differs from ANSI or POSIX, the latter forms are preferred.  In some cases, strace output is proven to be more readable than the source.
Structure pointers are dereferenced and the members are displayed as appropriate.  In most cases, arguments are formatted in the most C-like fashion possible.  For example, the essence of the command "ls -l /dev/null" is captured as:
lstat("/dev/null", {st_mode=S_IFCHR|0666, st_rdev=makedev(0x1, 0x3), ...}) = 0
Notice how the 'struct stat' argument is dereferenced and how each member is displayed symbolically.  In particular, observe how the st_mode member is carefully decoded into a bitwise-OR of symbolic and numeric values. Also notice in this example that the first argument to lstat(2) is an input to the system call and the second argument is an output.  Since output arguments are not modified if the system call fails, arguments may not always be dereferenced.  For example, retrying the "ls -l" example with a non-existent file produces the following line:
lstat("/foo/bar", 0xb004) = -1 ENOENT (No such file or directory)
In this case the porch light is on but nobody is home.
Syscalls unknown to strace are printed raw, with the unknown system call number printed in hexadecimal form and prefixed with "syscall_":
syscall_0xbad(0x1, 0x2, 0x3, 0x4, 0x5, 0x6) = -1 ENOSYS (Function not implemented)
Character pointers are dereferenced and printed as C strings.  Non- printing characters in strings are normally represented by ordinary C escape codes.  Only the first strsize (32 by default) bytes of strings are printed; longer strings have an ellipsis appended following the closing quote.  Here is a line from "ls -l" where the getpwuid(3) library routine is reading the password file:
read(3, "root::0:0:System Administrator:/"..., 1024) = 422
While structures are annotated using curly braces, simple pointers and arrays are printed using square brackets with commas separating elements. Here is an example from the command id(1) on a system with supplementary group ids:
getgroups(32, [100, 0]) = 2
On the other hand, bit-sets are also shown using square brackets, but set elements are separated only by a space.  Here is the shell, preparing to execute an external command:
sigprocmask(SIG_BLOCK, [CHLD TTOU], []) = 0
Here, the second argument is a bit-set of two signals, SIGCHLD and SIGTTOU.  In some cases, the bit-set is so full that printing out the unset elements is more valuable.  In that case, the bit-set is prefixed by a tilde like this:
sigprocmask(SIG_UNBLOCK, ~[], NULL) = 0
Here, the second argument represents the full set of all signals.
General -e expr     A qualifying expression which modifies which events to trace or how to trace them.  The format of the expression is:
[qualifier=][!]value[,value]...
where qualifier is one of trace (or t), abbrev (or a), verbose (or v), raw (or x), signal (or signals or s), read (or reads or r), write (or writes or w), fault, inject, status, quiet (or silent or silence or q), decode-fds (or decode-fd), decode-pids (or decode-pid), or kvm, and value is a qualifier-dependent symbol or number.  The default qualifier is trace.  Using an exclamation mark negates the set of values.  For example, -e open means literally -e trace=open which in turn means trace only the open system call.  By contrast, -e trace=!open means to trace every system call except open.  In addition, the special values all and none have the obvious meanings.
Note that some shells use the exclamation point for history expansion even inside quoted arguments.  If so, you must escape the exclamation point with a backslash.
Startup -E var=val --env=var=val Run command with var=val in its list of environment variables.
-E var --env=var   Remove var from the inherited list of environment variables before passing it on to the command.
-p pid --attach=pid Attach to the process with the process ID pid and begin tracing.  The trace may be terminated at any time by a keyboard interrupt signal (CTRL-C).  strace will respond by detaching itself from the traced process(es) leaving it (them) to continue running.  Multiple -p options can be used to attach to many processes in addition to command (which is optional if at least one -p option is given).  Multiple process IDs, separated by either comma (“,”), space (“ ”), tab, or newline character, can be provided as an argument to a single -p option, so, for example, -p "$(pidof PROG)" and -p "$(pgrep PROG)" syntaxes are supported.
-u username --user=username Run command with the user ID, group ID, and supplementary groups of username.  This option is only useful when running as root and enables the correct execution of setuid and/or setgid binaries.  Unless this option is used setuid and setgid programs are executed without effective privileges.
Tracing -b syscall --detach-on=syscall If specified syscall is reached, detach from traced process. Currently, only execve(2) syscall is supported.  This option is useful if you want to trace multi-threaded process and therefore require -f, but don't want to trace its (potentially very complex) children.
-D --daemonize --daemonize=grandchild Run tracer process as a grandchild, not as the parent of the tracee.  This reduces the visible effect of strace by keeping the tracee a direct child of the calling process.
-DD --daemonize=pgroup --daemonize=pgrp Run tracer process as tracee's grandchild in a separate process group.  In addition to reduction of the visible effect of strace, it also avoids killing of strace with kill(2) issued to the whole process group.
-DDD --daemonize=session Run tracer process as tracee's grandchild in a separate session ("true daemonisation").  In addition to reduction of the visible effect of strace, it also avoids killing of strace upon session termination.
-f --follow-forks Trace child processes as they are created by currently traced processes as a result of the fork(2), vfork(2) and clone(2) system calls.  Note that -p PID -f will attach all threads of process PID if it is multi-threaded, not only thread with thread_id = PID.
--output-separately If the --output=filename option is in effect, each processes trace is written to filename.pid where pid is the numeric process id of each process.
-ff --follow-forks --output-separately Combine the effects of --follow-forks and --output-separately options.  This is incompatible with -c, since no per-process counts are kept.
One might want to consider using strace-log-merge(1) to obtain a combined strace log view.
-I interruptible --interruptible=interruptible When strace can be interrupted by signals (such as pressing CTRL-C).
1, anywhere    no signals are blocked; 2, waiting     fatal signals are blocked while decoding syscall (default); 3, never       fatal signals are always blocked (default if -o FILE PROG); 4, never_tstp  fatal signals and SIGTSTP (CTRL-Z) are always blocked (useful to make strace -o FILE PROG not stop on CTRL-Z, default if -D).
Filtering -e trace=syscall_set --trace=syscall_set Trace only the specified set of system calls.  syscall_set is defined as [!]value[,value], and value can be one of the following:
syscall      Trace specific syscall, specified by its name (but see NOTES).
?value       Question mark before the syscall qualification allows suppression of error in case no syscalls matched the qualification provided.
/regex       Trace only those system calls that match the regex.  You can use POSIX Extended Regular Expression syntax (see regex(7)).
syscall@64   Trace syscall only for the 64-bit personality.
syscall@32   Trace syscall only for the 32-bit personality.
syscall@x32  Trace syscall only for the 32-on-64-bit personality.
%file file         Trace all system calls which take a file name as an argument.  You can think of this as an abbreviation for -e trace=open,stat,chmod,unlink,...  which is useful to seeing what files the process is referencing.  Furthermore, using the abbreviation will ensure that you don't accidentally forget to include a call like lstat(2) in the list.  Betchya woulda forgot that one.  The syntax without a preceding percent sign ("-e trace=file") is deprecated.
%process process      Trace system calls associated with process lifecycle (creation, exec, termination).  The syntax without a preceding percent sign ("-e trace=process") is deprecated.
%net %network network      Trace all the network related system calls.  The syntax without a preceding percent sign ("-e trace=network") is deprecated.
%signal signal       Trace all signal related system calls.  The syntax without a preceding percent sign ("-e trace=signal") is deprecated.
%ipc ipc          Trace all IPC related system calls.  The syntax without a preceding percent sign ("-e trace=ipc") is deprecated.
%desc desc         Trace all file descriptor related system calls. The syntax without a preceding percent sign ("-e trace=desc") is deprecated.
%memory memory       Trace all memory mapping related system calls. The syntax without a preceding percent sign ("-e trace=memory") is deprecated.
%creds       Trace system calls that read or modify user and group identifiers or capability sets.
%stat        Trace stat syscall variants.
%lstat       Trace lstat syscall variants.
%fstat       Trace fstat, fstatat, and statx syscall variants.
%%stat       Trace syscalls used for requesting file status (stat, lstat, fstat, fstatat, statx, and their variants).
%statfs      Trace statfs, statfs64, statvfs, osf_statfs, and osf_statfs64 system calls.  The same effect can be achieved with -e trace=/^(.*_)?statv?fs regular expression.
%fstatfs     Trace fstatfs, fstatfs64, fstatvfs, osf_fstatfs, and osf_fstatfs64 system calls.  The same effect can be achieved with -e trace=/fstatv?fs regular expression.
%%statfs     Trace syscalls related to file system statistics (statfs-like, fstatfs-like, and ustat).  The same effect can be achieved with -e trace=/statv?fs|fsstat|ustat regular expression.
%clock       Trace system calls that read or modify system clocks.
%pure        Trace syscalls that always succeed and have no arguments.  Currently, this list includes arc_gettls(2), getdtablesize(2), getegid(2), getegid32(2), geteuid(2), geteuid32(2), getgid(2), getgid32(2), getpagesize(2), getpgrp(2), getpid(2), getppid(2), get_thread_area(2) (on architectures other than x86), gettid(2), get_tls(2), getuid(2), getuid32(2), getxgid(2), getxpid(2), getxuid(2), kern_features(2), and metag_get_tls(2) syscalls.
The -c option is useful for determining which system calls might be useful to trace.  For example, trace=open,close,read,write means to only trace those four system calls.  Be careful when making inferences about the user/kernel boundary if only a subset of system calls are being monitored.  The default is trace=all.
-e signal=set --signal=set Trace only the specified subset of signals.  The default is signal=all.  For example, signal=!SIGIO (or signal=!io) causes SIGIO signals not to be traced.
-e status=set --status=set Print only system calls with the specified return status. The default is status=all.  When using the status qualifier, because strace waits for system calls to return before deciding whether they should be printed or not, the traditional order of events may not be preserved anymore.  If two system calls are executed by concurrent threads, strace will first print both the entry and exit of the first system call to exit, regardless of their respective entry time.  The entry and exit of the second system call to exit will be printed afterwards.  Here is an example when select(2) is called, but a different thread calls clock_gettime(2) before select(2) finishes:
[pid 28779] 1130322148.939977 clock_gettime(CLOCK_REALTIME, {1130322148, 939977000}) = 0 [pid 28772] 1130322148.438139 select(4, [3], NULL, NULL, NULL) = 1 (in [3])
set can include the following elements:
successful   Trace system calls that returned without an error code.  The -z option has the effect of status=successful. failed       Trace system calls that returned with an error code.  The -Z option has the effect of status=failed. unfinished   Trace system calls that did not return.  This might happen, for example, due to an execve call in a neighbour thread. unavailable  Trace system calls that returned but strace failed to fetch the error status. detached     Trace system calls for which strace detached before the return.
-P path --trace-path=path Trace only system calls accessing path.  Multiple -P options can be used to specify several paths.
-z --successful-only Print only syscalls that returned without an error code.
-Z --failed-only Print only syscalls that returned with an error code.
Output format -a column --columns=column Align return values in a specific column (default column 40).
-e abbrev=syscall_set --abbrev=syscall_set Abbreviate the output from printing each member of large structures.  The syntax of the syscall_set specification is the same as in the -e trace option.  The default is abbrev=all.  The -v option has the effect of abbrev=none.
-e verbose=syscall_set --verbose=syscall_set Dereference structures for the specified set of system calls. The syntax of the syscall_set specification is the same as in the -e trace option.  The default is verbose=all.
-e raw=syscall_set --raw=syscall_set Print raw, undecoded arguments for the specified set of system calls.  The syntax of the syscall_set specification is the same as in the -e trace option.  This option has the effect of causing all arguments to be printed in hexadecimal. This is mostly useful if you don't trust the decoding or you need to know the actual numeric value of an argument.  See also -X raw option.
-e read=set --read=set  Perform a full hexadecimal and ASCII dump of all the data read from file descriptors listed in the specified set.  For example, to see all input activity on file descriptors 3 and 5 use -e read=3,5.  Note that this is independent from the normal tracing of the read(2) system call which is controlled by the option -e trace=read.
-e write=set --write=set Perform a full hexadecimal and ASCII dump of all the data written to file descriptors listed in the specified set.  For example, to see all output activity on file descriptors 3 and 5 use -e write=3,5.  Note that this is independent from the normal tracing of the write(2) system call which is controlled by the option -e trace=write.
-e quiet=set --quiet=set --silent=set --silence=set Suppress various information messages.  The default is quiet=none.  set can include the following elements:
attach           Suppress messages about attaching and detaching ("[ Process NNNN attached ]", "[ Process NNNN detached ]"). exit             Suppress messages about process exits ("+++ exited with SSS +++"). path-resolution  Suppress messages about resolution of paths provided via the -P option ("Requested path "..." resolved into "...""). personality      Suppress messages about process personality changes ("[ Process PID=NNNN runs in PPP mode. ]"). thread-execve superseded       Suppress messages about process being superseded by execve(2) in another thread ("+++ superseded by execve in pid NNNN +++").
-e decode-fds=set --decode-fds=set Decode various information associated with file descriptors. The default is decode-fds=none.  set can include the following elements:
path    Print file paths.  Also enables printing of tracee's current working directory when AT_FDCWD constant is used. socket  Print socket protocol-specific information, dev     Print character/block device numbers. pidfd   Print PIDs associated with pidfd file descriptors.
-e decode-pids=set --decode-pids=set Decode various information associated with process IDs (and also thread IDs, process group IDs, and session IDs).  The default is decode-pids=none.  set can include the following elements:
comm    Print command names associated with thread or process IDs. pidns   Print thread, process, process group, and session IDs in strace's PID namespace if the tracee is in a different PID namespace.
-e kvm=vcpu --kvm=vcpu  Print the exit reason of kvm vcpu.  Requires Linux kernel version 4.16.0 or higher.
-i --instruction-pointer Print the instruction pointer at the time of the system call.
-n --syscall-number Print the syscall number.
-k --stack-traces Print the execution stack trace of the traced processes after each system call.
-o filename --output=filename Write the trace output to the file filename rather than to stderr.  filename.pid form is used if -ff option is supplied. If the argument begins with '|' or '!', the rest of the argument is treated as a command and all output is piped to it.  This is convenient for piping the debugging output to a program without affecting the redirections of executed programs.  The latter is not compatible with -ff option currently.
-A --output-append-mode Open the file provided in the -o option in append mode.
-q --quiet --quiet=attach,personality Suppress messages about attaching, detaching, and personality changes.  This happens automatically when output is redirected to a file and the command is run directly instead of attaching.
-qq --quiet=attach,personality,exit Suppress messages attaching, detaching, personality changes, and about process exit status.
-qqq --quiet=all Suppress all suppressible messages (please refer to the -e quiet option description for the full list of suppressible messages).
-r --relative-timestamps[=precision] Print a relative timestamp upon entry to each system call. This records the time difference between the beginning of successive system calls.  precision can be one of s (for seconds), ms (milliseconds), us (microseconds), or ns (nanoseconds), and allows setting the precision of time value being printed.  Default is us (microseconds).  Note that since -r option uses the monotonic clock time for measuring time difference and not the wall clock time, its measurements can differ from the difference in time reported by the -t option.
-s strsize --string-limit=strsize Specify the maximum string size to print (the default is 32). Note that filenames are not considered strings and are always printed in full.
--absolute-timestamps[=[[format:]format],[[precision:]precision]] --timestamps[=[[format:]format],[[precision:]precision]] Prefix each line of the trace with the wall clock time in the specified format with the specified precision.  format can be one of the following:
none          No time stamp is printed.  Can be used to override the previous setting. time          Wall clock time (strftime(3) format string is %T). unix          Number of seconds since the epoch (strftime(3) format string is %s).
precision can be one of s (for seconds), ms (milliseconds), us (microseconds), or ns (nanoseconds).  Default arguments for the option are format:time,precision:s.
-t --absolute-timestamps Prefix each line of the trace with the wall clock time.
-tt --absolute-timestamps=precision:us If given twice, the time printed will include the microseconds.
-ttt --absolute-timestamps=format:unix,precision:us If given thrice, the time printed will include the microseconds and the leading portion will be printed as the number of seconds since the epoch.
-T --syscall-times[=precision] Show the time spent in system calls.  This records the time difference between the beginning and the end of each system call.  precision can be one of s (for seconds), ms (milliseconds), us (microseconds), or ns (nanoseconds), and allows setting the precision of time value being printed. Default is us (microseconds).
-v --no-abbrev Print unabbreviated versions of environment, stat, termios, etc.  calls.  These structures are very common in calls and so the default behavior displays a reasonable subset of structure members.  Use this option to get all of the gory details.
--strings-in-hex[=option] Control usage of escape sequences with hexadecimal numbers in the printed strings.  Normally (when no --strings-in-hex or -x option is supplied), escape sequences are used to print non-printable and non-ASCII characters (that is, characters with a character code less than 32 or greater than 127), or to disambiguate the output (so, for quotes and other characters that encase the printed string, for example, angle brackets, in case of file descriptor path output); for the former use case, unless it is a white space character that has a symbolic escape sequence defined in the C standard (that is, “\t” for a horizontal tab, “\n” for a newline, “\v” for a vertical tab, “\f” for a form feed page break, and “\r” for a carriage return) are printed using escape sequences with numbers that correspond to their byte values, with octal number format being the default.  option can be one of the following:
none             Hexadecimal numbers are not used in the output at all.  When there is a need to emit an escape sequence, octal numbers are used. non-ascii-chars  Hexadecimal numbers are used instead of octal in the escape sequences. non-ascii        Strings that contain non-ASCII characters are printed using escape sequences with hexadecimal numbers. all              All strings are printed using escape sequences with hexadecimal numbers.
When the option is supplied without an argument, all is assumed.
-x --strings-in-hex=non-ascii Print all non-ASCII strings in hexadecimal string format.
-xx --strings-in-hex[=all] Print all strings in hexadecimal string format.
-X format --const-print-style=format Set the format for printing of named constants and flags. Supported format values are:
raw       Raw number output, without decoding. abbrev    Output a named constant or a set of flags instead of the raw number if they are found.  This is the default strace behaviour. verbose   Output both the raw value and the decoded string (as a comment).
-y --decode-fds --decode-fds=path Print paths associated with file descriptor arguments and with the AT_FDCWD constant.
-yy --decode-fds=all Print all available information associated with file descriptors: protocol-specific information associated with socket file descriptors, block/character device number associated with device file descriptors, and PIDs associated with pidfd file descriptors.
--pidns-translation --decode-pids=pidns If strace and tracee are in different PID namespaces, print PIDs in strace's namespace, too.
-Y --decode-pids=comm Print command names for PIDs.
Statistics -c --summary-only Count time, calls, and errors for each system call and report a summary on program exit, suppressing the regular output. This attempts to show system time (CPU time spent running in the kernel) independent of wall clock time.  If -c is used with -f, only aggregate totals for all traced processes are kept.
-C --summary   Like -c but also print regular output while processes are running.
-O overhead --summary-syscall-overhead=overhead Set the overhead for tracing system calls to overhead.  This is useful for overriding the default heuristic for guessing how much time is spent in mere measuring when timing system calls using the -c option.  The accuracy of the heuristic can be gauged by timing a given program run without tracing (using time(1)) and comparing the accumulated system call time to the total produced using -c.
The format of overhead specification is described in section Time specification format description.
-S sortby --summary-sort-by=sortby Sort the output of the histogram printed by the -c option by the specified criterion.  Legal values are time (or time-percent or time-total or total-time), min-time (or shortest or time-min), max-time (or longest or time-max), avg-time (or time-avg), calls (or count), errors (or error), name (or syscall or syscall-name), and nothing (or none); default is time.
-U columns --summary-columns=columns Configure a set (and order) of columns being shown in the call summary.  The columns argument is a comma-separated list with items being one of the following:
time-percent (or time)              Percentage of cumulative time consumed by a specific system call. total-time (or time-total)          Total system (or wall clock, if -w option is provided) time consumed by a specific system call. min-time (or shortest or time-min)  Minimum observed call duration. max-time (or longest or time-max)   Maximum observed call duration. avg-time (or time-avg)              Average call duration. calls (or count)                    Call count. errors (or error)                   Error count. name (or syscall or syscall-name)   Syscall name.
The default value is time-percent,total-time,avg-time,calls,errors,name.  If the name field is not supplied explicitly, it is added as the last column.
-w --summary-wall-clock Summarise the time difference between the beginning and end of each system call.  The default is to summarise the system time.
Tampering -e inject=syscall_set[:error=errno|:retval=value][:signal=sig][:syscall=syscall][:delay_enter=delay][:delay_exit=delay][:poke_enter=@argN=DATAN,@argM=DATAM...][:poke_exit=@argN=DATAN,@argM=DATAM...][:when=expr] --inject=syscall_set[:error=errno|:retval=value][:signal=sig][:syscall=syscall][:delay_enter=delay][:delay_exit=delay][:poke_enter=@argN=DATAN,@argM=DATAM...][:poke_exit=@argN=DATAN,@argM=DATAM...][:when=expr] Perform syscall tampering for the specified set of syscalls. The syntax of the syscall_set specification is the same as in the -e trace option.
At least one of error, retval, signal, delay_enter, delay_exit, poke_enter, or poke_exit options has to be specified.  error and retval are mutually exclusive.
If :error=errno option is specified, a fault is injected into a syscall invocation: the syscall number is replaced by -1 which corresponds to an invalid syscall (unless a syscall is specified with :syscall= option), and the error code is specified using a symbolic errno value like ENOSYS or a numeric value within 1..4095 range.
If :retval=value option is specified, success injection is performed: the syscall number is replaced by -1, but a bogus success value is returned to the callee.
If :signal=sig option is specified with either a symbolic value like SIGSEGV or a numeric value within 1..SIGRTMAX range, that signal is delivered on entering every syscall specified by the set.
If :delay_enter=delay or :delay_exit=delay options are specified, delay injection is performed: the tracee is delayed by time period specified by delay on entering or exiting the syscall, respectively.  The format of delay specification is described in section Time specification format description.
If :poke_enter=@argN=DATAN,@argM=DATAM...  or :poke_exit=@argN=DATAN,@argM=DATAM... options are specified, tracee's memory at locations, pointed to by system call arguments argN and argM (going from arg1 to arg7) is overwritten by data DATAN and DATAM (specified in hexadecimal format; for example :poke_enter=@arg1=0000DEAD0000BEEF). :poke_enter modifies memory on syscall enter, and :poke_exit - on exit.
If :signal=sig option is specified without :error=errno, :retval=value or :delay_{enter,exit}=usecs options, then only a signal sig is delivered without a syscall fault or delay injection.  Conversely, :error=errno or :retval=value option without :delay_enter=delay, :delay_exit=delay or :signal=sig options injects a fault without delivering a signal or injecting a delay, etc.
If :signal=sig option is specified together with :error=errno or :retval=value, then both injection of a fault or success and signal delivery are performed.
if :syscall=syscall option is specified, the corresponding syscall with no side effects is injected instead of -1. Currently, only "pure" (see -e trace=%pure description) syscalls can be specified there.
Unless a :when=expr subexpression is specified, an injection is being made into every invocation of each syscall from the set.
The format of the subexpression is:
first[..last][+[step]]
Number first stands for the first invocation number in the range, number last stands for the last invocation number in the range, and step stands for the step between two consecutive invocations.  The following combinations are useful:
first             For every syscall from the set, perform an injection for the syscall invocation number first only. first..last       For every syscall from the set, perform an injection for the syscall invocation number first and all subsequent invocations until the invocation number last (inclusive). first+            For every syscall from the set, perform injections for the syscall invocation number first and all subsequent invocations. first..last+      For every syscall from the set, perform injections for the syscall invocation number first and all subsequent invocations until the invocation number last (inclusive). first+step        For every syscall from the set, perform injections for syscall invocations number first, first+step, first+step+step, and so on. first..last+step  Same as the previous, but consider only syscall invocations with numbers up to last (inclusive).
For example, to fail each third and subsequent chdir syscalls with ENOENT, use -e inject=chdir:error=ENOENT:when=3+.
The valid range for numbers first and step is 1..65535, and for number last is 1..65534.
An injection expression can contain only one error= or retval= specification, and only one signal= specification. If an injection expression contains multiple when= specifications, the last one takes precedence.
Accounting of syscalls that are subject to injection is done per syscall and per tracee.
Specification of syscall injection can be combined with other syscall filtering options, for example, -P /dev/urandom -e inject=file:error=ENOENT.
-e fault=syscall_set[:error=errno][:when=expr] --fault=syscall_set[:error=errno][:when=expr] Perform syscall fault injection for the specified set of syscalls.
This is equivalent to more generic -e inject= expression with default value of errno option set to ENOSYS.
Miscellaneous -d --debug     Show some debugging output of strace itself on the standard error.
-F          This option is deprecated.  It is retained for backward compatibility only and may be removed in future releases. Usage of multiple instances of -F option is still equivalent to a single -f, and it is ignored at all if used along with one or more instances of -f option.
-h --help      Print the help summary.
--seccomp-bpf Try to enable use of seccomp-bpf (see seccomp(2)) to have ptrace(2)-stops only when system calls that are being traced occur in the traced processes.  This option has no effect unless -f/--follow-forks is also specified.  --seccomp-bpf is also not applicable to processes attached using -p/--attach option.  An attempt to enable system calls filtering using seccomp-bpf may fail for various reasons, e.g. there are too many system calls to filter, the seccomp API is not available, or strace itself is being traced.  In cases when seccomp-bpf filter setup failed, strace proceeds as usual and stops traced processes on every system call.
-V --version   Print the version number of strace.
Time specification format description Time values can be specified as a decimal floating point number (in a format accepted by strtod(3)), optionally followed by one of the following suffices that specify the unit of time: s (seconds), ms (milliseconds), us (microseconds), or ns (nanoseconds).  If no suffix is specified, the value is interpreted as microseconds.
The described format is used for -O, -e inject=delay_enter, and -e inject=delay_exit options.
When command exits, strace exits with the same exit status.  If command is terminated by a signal, strace terminates itself with the same signal, so that strace can be used as a wrapper process transparent to the invoking parent process.  Note that parent-child relationship (signal stop notifications, getppid(2) value, etc) between traced process and its parent are not preserved unless -D is used.
When using -p without a command, the exit status of strace is zero unless no processes has been attached or there was an unexpected error in doing the tracing.
If strace is installed setuid to root then the invoking user will be able to attach to and trace processes owned by any user.  In addition setuid and setgid programs will be executed and traced with the correct effective privileges.  Since only users trusted with full root privileges should be allowed to do these things, it only makes sense to install strace as setuid to root when the users who can execute it are restricted to those users who have this trust.  For example, it makes sense to install a special version of strace with mode 'rwsr-xr--', user root and group trace, where members of the trace group are trusted users.  If you do use this feature, please remember to install a regular non-setuid version of strace for ordinary users to use.
On some architectures, strace supports decoding of syscalls for processes that use different ABI rather than the one strace uses.  Specifically, in addition to decoding native ABI, strace can decode the following ABIs on the following architectures:
┌───────────────────┬─────────────────────────┐ │Architecture       │ ABIs supported          │ ├───────────────────┼─────────────────────────┤ │x86_64             │ i386, x32 [1]; i386 [2] │ ├───────────────────┼─────────────────────────┤ │AArch64            │ ARM 32-bit EABI         │ ├───────────────────┼─────────────────────────┤ │PowerPC 64-bit [3] │ PowerPC 32-bit          │ ├───────────────────┼─────────────────────────┤ │s390x              │ s390                    │ ├───────────────────┼─────────────────────────┤ │SPARC 64-bit       │ SPARC 32-bit            │ ├───────────────────┼─────────────────────────┤ │TILE 64-bit        │ TILE 32-bit             │ └───────────────────┴─────────────────────────┘ [1]  When strace is built as an x86_64 application [2]  When strace is built as an x32 application [3]  Big endian only
This support is optional and relies on ability to generate and parse structure definitions during the build time.  Please refer to the output of the strace -V command in order to figure out what support is available in your strace build ("non-native" refers to an ABI that differs from the ABI strace has):
m32-mpers      strace can trace and properly decode non-native 32-bit binaries. no-m32-mpers   strace can trace, but cannot properly decode non-native 32-bit binaries. mx32-mpers     strace can trace and properly decode non-native 32-on-64-bit binaries. no-mx32-mpers  strace can trace, but cannot properly decode non-native 32-on-64-bit binaries.
If the output contains neither m32-mpers nor no-m32-mpers, then decoding of non-native 32-bit binaries is not implemented at all or not applicable.
Likewise, if the output contains neither mx32-mpers nor no-mx32-mpers, then decoding of non-native 32-on-64-bit binaries is not implemented at all or not applicable.
It is a pity that so much tracing clutter is produced by systems employing shared libraries.
It is instructive to think about system call inputs and outputs as data- flow across the user/kernel boundary.  Because user-space and kernel- space are separate and address-protected, it is sometimes possible to make deductive inferences about process behavior using inputs and outputs as propositions.