1MKDIR(3P)                  POSIX Programmer's Manual                 MKDIR(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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11

NAME

13       mkdir, mkdirat — make a directory relative to directory file descriptor
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SYNOPSIS

16       #include <sys/stat.h>
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18       int mkdir(const char *path, mode_t mode);
19       int mkdirat(int fd, const char *path, mode_t mode);
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DESCRIPTION

22       The mkdir() function shall create a new directory with name path.   The
23       file  permission  bits  of  the new directory shall be initialized from
24       mode.  These file permission bits of the mode argument shall  be  modi‐
25       fied by the process' file creation mask.
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27       When  bits  in  mode  other  than the file permission bits are set, the
28       meaning of these additional bits is implementation-defined.
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30       The directory's user ID shall be set to the process' effective user ID.
31       The  directory's  group  ID  shall be set to the group ID of the parent
32       directory or to the effective group ID of the process.  Implementations
33       shall provide a way to initialize the directory's group ID to the group
34       ID of the parent directory. Implementations may, but need not,  provide
35       an implementation-defined way to initialize the directory's group ID to
36       the effective group ID of the calling process.
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38       The newly created directory shall be an empty directory.
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40       If path names a symbolic link, mkdir() shall  fail  and  set  errno  to
41       [EEXIST].
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43       Upon successful completion, mkdir() shall mark for update the last data
44       access, last data modification, and last file status change  timestamps
45       of the directory. Also, the last data modification and last file status
46       change timestamps of the directory that contains the new entry shall be
47       marked for update.
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49       The  mkdirat()  function  shall  be  equivalent to the mkdir() function
50       except in the case where path specifies a relative path. In  this  case
51       the  newly created directory is created relative to the directory asso‐
52       ciated with the file descriptor  fd  instead  of  the  current  working
53       directory.  If  the  file  descriptor  was opened without O_SEARCH, the
54       function shall check whether directory searches are permitted using the
55       current permissions of the directory underlying the file descriptor. If
56       the file descriptor was opened with O_SEARCH, the  function  shall  not
57       perform the check.
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59       If  mkdirat() is passed the special value AT_FDCWD in the fd parameter,
60       the current working directory shall be used and the behavior  shall  be
61       identical to a call to mkdir().
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RETURN VALUE

64       Upon successful completion, these functions shall return 0.  Otherwise,
65       these functions shall return −1 and set errno to indicate the error. If
66       −1 is returned, no directory shall be created.
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ERRORS

69       These functions shall fail if:
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71       EACCES Search  permission  is denied on a component of the path prefix,
72              or write permission is denied on the  parent  directory  of  the
73              directory to be created.
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75       EEXIST The named file exists.
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77       ELOOP  A loop exists in symbolic links encountered during resolution of
78              the path argument.
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80       EMLINK The link count of the parent directory would exceed {LINK_MAX}.
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82       ENAMETOOLONG
83              The  length  of  a  component  of  a  pathname  is  longer  than
84              {NAME_MAX}.
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86       ENOENT A  component  of the path prefix specified by path does not name
87              an existing directory or path is an empty string.
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89       ENOSPC The file system does not contain enough space to hold  the  con‐
90              tents  of the new directory or to extend the parent directory of
91              the new directory.
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93       ENOTDIR
94              A component of the path prefix names an existing  file  that  is
95              neither a directory nor a symbolic link to a directory.
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97       EROFS  The parent directory resides on a read-only file system.
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99       In addition, the mkdirat() function shall fail if:
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101       EBADF  The  path  argument does not specify an absolute path and the fd
102              argument is neither AT_FDCWD nor a valid  file  descriptor  open
103              for reading or searching.
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105       ENOTDIR
106              The  path  argument  is  not  an  absolute path and fd is a file
107              descriptor associated with a non-directory file.
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109       These functions may fail if:
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111       ELOOP  More than {SYMLOOP_MAX} symbolic links were  encountered  during
112              resolution of the path argument.
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114       ENAMETOOLONG
115              The length of a pathname exceeds {PATH_MAX}, or pathname resolu‐
116              tion of a symbolic link produced an intermediate result  with  a
117              length that exceeds {PATH_MAX}.
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119       The following sections are informative.
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EXAMPLES

122   Creating a Directory
123       The   following   example   shows  how  to  create  a  directory  named
124       /home/cnd/mod1, with read/write/search permissions for owner and group,
125       and with read/search permissions for others.
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127           #include <sys/types.h>
128           #include <sys/stat.h>
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130           int status;
131           ...
132           status = mkdir("/home/cnd/mod1", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
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APPLICATION USAGE

135       None.
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RATIONALE

138       The mkdir() function originated in 4.2 BSD and was added to System V in
139       Release 3.0.
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141       4.3 BSD detects [ENAMETOOLONG].
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143       The POSIX.1‐1990 standard required that the group ID of a newly created
144       directory  be  set  to  the  group ID of its parent directory or to the
145       effective group ID of the creating process. FIPS  151‐2  required  that
146       implementations  provide a way to have the group ID be set to the group
147       ID of the containing directory, but did  not  prohibit  implementations
148       also  supporting a way to set the group ID to the effective group ID of
149       the creating process.  Conforming applications should not assume  which
150       group ID will be used. If it matters, an application can use chown() to
151       set the group ID after the directory is  created,  or  determine  under
152       what conditions the implementation will set the desired group ID.
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154       The  purpose  of  the  mkdirat()  function  is to create a directory in
155       directories other than the current working directory  without  exposure
156       to  race conditions. Any part of the path of a file could be changed in
157       parallel to the call to mkdir(), resulting in unspecified behavior.  By
158       opening  a file descriptor for the target directory and using the mkdi‐
159       rat() function it can be guaranteed that the newly created directory is
160       located relative to the desired directory.
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FUTURE DIRECTIONS

163       None.
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SEE ALSO

166       chmod(), mkdtemp(), mknod(), umask()
167
168       The    Base   Definitions   volume   of   POSIX.1‐2008,   <sys_stat.h>,
169       <sys_types.h>
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172       Portions of this text are reprinted and reproduced in  electronic  form
173       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
174       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
175       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
176       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
177       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
178       event of any discrepancy between this version and the original IEEE and
179       The  Open Group Standard, the original IEEE and The Open Group Standard
180       is the referee document. The original Standard can be  obtained  online
181       at http://www.unix.org/online.html .
182
183       Any  typographical  or  formatting  errors that appear in this page are
184       most likely to have been introduced during the conversion of the source
185       files  to  man page format. To report such errors, see https://www.ker
186       nel.org/doc/man-pages/reporting_bugs.html .
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190IEEE/The Open Group                  2013                            MKDIR(3P)
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