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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 relative to directory file descriptor

SYNOPSIS

       #include <sys/stat.h>

       int mkdir(const char *path, mode_t mode);
       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 file descriptor was opened without O_SEARCH, the function shall
       check whether directory searches are  permitted  using  the  current  permissions  of  the
       directory underlying the file descriptor. If the file descriptor was opened with 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:

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.

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2013 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/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 .