MKDIR(3)                   POSIX Programmer's Manual                  MKDIR(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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 aa 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.

SEE ALSO
       chmod(), mkdtemp(), mknod(), umask()

       The Base Definitions volume of POSIX.1-2017, <fcntl.h>, <sys_stat.h>,
       <sys_types.h>

COPYRIGHT
       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                             MKDIR(3)
