# mkdir

## PROLOG



           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



           mkdir, mkdirat — make a directory
    


## SYNOPSIS



           #include <sys/stat.h>
    
           int mkdir(const char *_path_ , mode_t _mode_);
    
           #include <fcntl.h>
    
           int mkdirat(int _fd_ , const char *_path_ , mode_t _mode_);
    


## DESCRIPTION



           The _mkdir_() function shall create a new directory with name _path_.
           The file permission bits of the new directory shall be initialized
           from _mode_.  These file permission bits of the _mode_ argument shall
           be modified by the process' file creation mask.
    
           When bits in _mode_ other than the file permission bits are set, the
           meaning of these additional bits is implementation-defined.
    
           The directory's user ID shall be set to the process' effective
           user ID.  The directory's group ID shall be set to the group ID of
           the parent directory or to the effective group ID of the process.
           Implementations shall provide a way to initialize the directory's
           group ID to the group ID of the parent directory. Implementations
           may, but need not, provide an implementation-defined way to
           initialize the directory's group ID to the effective group ID of
           the calling process.
    
           The newly created directory shall be an empty directory.
    
           If _path_ names a symbolic link, _mkdir_() shall fail and set _errno_ to
           **[EEXIST]**.
    
           Upon successful completion, _mkdir_() shall mark for update the last
           data access, last data modification, and last file status change
           timestamps of the directory. Also, the last data modification and
           last file status change timestamps of the directory that contains
           the new entry shall be marked for update.
    
           The _mkdirat_() function shall be equivalent to the _mkdir_() function
           except in the case where _path_ specifies a relative path. In this
           case the newly created directory is created relative to the
           directory associated with the file descriptor _fd_ instead of the
           current working directory. If the access mode of the open file
           description associated with the file descriptor is not O_SEARCH,
           the function shall check whether directory searches are permitted
           using the current permissions of the directory underlying the file
           descriptor. If the access mode is O_SEARCH, the function shall not
           perform the check.
    
           If _mkdirat_() is passed the special value AT_FDCWD in the _fd_
           parameter, the current working directory shall be used and the
           behavior shall be identical to a call to _mkdir_().
    


## RETURN VALUE



           Upon successful completion, these functions shall return 0.
           Otherwise, these functions shall return -1 and set _errno_ to
           indicate the error. If -1 is returned, no directory shall be
           created.
    


## ERRORS



           These functions shall fail if:
    
           **EACCES** Search permission is denied on a component of the path
                  prefix, or write permission is denied on the parent
                  directory of the directory to be created.
    
           **EEXIST** The named file exists.
    
           **ELOOP** A loop exists in symbolic links encountered during
                  resolution of the _path_ argument.
    
           **EMLINK** The link count of the parent directory would exceed
                  {LINK_MAX}.
    
           **ENAMETOOLONG**
                  The length of a component of a pathname is longer than
                  {NAME_MAX}.
    
           **ENOENT** A component of the path prefix specified by _path_ does not
                  name an existing directory or _path_ is an empty string.
    
           **ENOSPC** The file system does not contain enough space to hold the
                  contents of the new directory or to extend the parent
                  directory of the new directory.
    
           **ENOTDIR**
                  A component of the path prefix names an existing file that
                  is neither a directory nor a symbolic link to a directory.
    
           **EROFS** The parent directory resides on a read-only file system.
    
           In addition, the _mkdirat_() function shall fail if:
    
           **EACCES** The access mode of the open file description associated
                  with _fd_ is not O_SEARCH and the permissions of the
                  directory underlying _fd_ do not permit directory searches.
    
           **EBADF** The _path_ argument does not specify an absolute path and the
                  _fd_ argument is neither AT_FDCWD nor a valid file descriptor
                  open for reading or searching.
    
           **ENOTDIR**
                  The _path_ argument is not an absolute path and _fd_ is a file
                  descriptor associated with a non-directory file.
    
           These functions may fail if:
    
           **ELOOP** More than {SYMLOOP_MAX} symbolic links were encountered
                  during resolution of the _path_ argument.
    
           **ENAMETOOLONG**
                  The length of a pathname exceeds {PATH_MAX}, or pathname
                  resolution of a symbolic link produced an intermediate
                  result with a length that exceeds {PATH_MAX}.
    
           _The following sections are informative._
    


## EXAMPLES



       **Creating a Directory**
           The following example shows how to create a directory named
           **/home/cnd/mod1** , with read/write/search permissions for owner and
           group, and with read/search permissions for others.
    
               #include <sys/types.h>
               #include <sys/stat.h>
    
               int status;
               ...
               status = mkdir("/home/cnd/mod1", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
    


## APPLICATION USAGE



           None.
    


## RATIONALE



           The _mkdir_() function originated in 4.2 BSD and was added to System
           V in Release 3.0.
    
           4.3 BSD detects **[ENAMETOOLONG]**.
    
           The POSIX.1‐1990 standard required that the group ID of a newly
           created directory be set to the group ID of its parent directory
           or to the effective group ID of the creating process. FIPS 151‐2
           required that implementations provide a way to have the group ID
           be set to the group ID of the containing directory, but did not
           prohibit implementations also supporting a way to set the group ID
           to the effective group ID of the creating process.  Conforming
           applications should not assume which group ID will be used. If it
           matters, an application can use _chown_() to set the group ID after
           the directory is created, or determine under what conditions the
           implementation will set the desired group ID.
    
           The purpose of the _mkdirat_() function is to create a directory in
           directories other than the current working directory without
           exposure to race conditions. Any part of the path of a file could
           be changed in parallel to the call to _mkdir_(), resulting in
           unspecified behavior. By opening a file descriptor for the target
           directory and using the _mkdirat_() function it can be guaranteed
           that the newly created directory is located relative to the
           desired directory.
    


## FUTURE DIRECTIONS



           None.
    


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