Ubuntu Manpage: This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

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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

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.

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(3POSIX)