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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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MKDIR(3P) POSIX Programmer's Manual MKDIR(3P)
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.
mkdir, mkdirat — make a directory
#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);
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().
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.
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.
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);
None.
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.
None.
chmod(3p), mkdtemp(3p), mknod(3p), umask(3p)
The Base Definitions volume of POSIX.1‐2017, fcntl.h(0p),
sys_stat.h(0p), sys_types.h(0p)
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(3P)
Pages that refer to this page: sys_stat.h(0p), mkdir(1p), pax(1p), chmod(3p), mkdtemp(3p), mknod(3p), rmdir(3p), umask(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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