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mkdir(2) System Calls Manual mkdir(2)


mkdir, mkdirat - create a directory


Standard C library (libc, -lc)


#include <sys/stat.h>
int mkdir(const char *pathname, mode_t mode);
#include <fcntl.h>           /* Definition of AT_* constants */
#include <sys/stat.h>
int mkdirat(int dirfd, const char *pathname, mode_t mode);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):


Since glibc 2.10:
_POSIX_C_SOURCE >= 200809L
Before glibc 2.10:


mkdir() attempts to create a directory named pathname.

The argument mode specifies the mode for the new directory (see inode(7)). It is modified by the process's umask in the usual way: in the absence of a default ACL, the mode of the created directory is (mode & ~umask & 0777). Whether other mode bits are honored for the created directory depends on the operating system. For Linux, see NOTES below.

The newly created directory will be owned by the effective user ID of the process. If the directory containing the file has the set-group-ID bit set, or if the filesystem is mounted with BSD group semantics (mount -o bsdgroups or, synonymously mount -o grpid), the new directory will inherit the group ownership from its parent; otherwise it will be owned by the effective group ID of the process.

If the parent directory has the set-group-ID bit set, then so will the newly created directory.


The mkdirat() system call operates in exactly the same way as mkdir(), except for the differences described here.

If the pathname given in pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor dirfd (rather than relative to the current working directory of the calling process, as is done by mkdir() for a relative pathname).

If pathname is relative and dirfd is the special value AT_FDCWD, then pathname is interpreted relative to the current working directory of the calling process (like mkdir()).

If pathname is absolute, then dirfd is ignored.

See openat(2) for an explanation of the need for mkdirat().


mkdir() and mkdirat() return zero on success. On error, -1 is returned and errno is set to indicate the error.


The parent directory does not allow write permission to the process, or one of the directories in pathname did not allow search permission. (See also path_resolution(7).)
(mkdirat()) pathname is relative but dirfd is neither AT_FDCWD nor a valid file descriptor.
The user's quota of disk blocks or inodes on the filesystem has been exhausted.
pathname already exists (not necessarily as a directory). This includes the case where pathname is a symbolic link, dangling or not.
pathname points outside your accessible address space.
The final component ("basename") of the new directory's pathname is invalid (e.g., it contains characters not permitted by the underlying filesystem).
Too many symbolic links were encountered in resolving pathname.
The number of links to the parent directory would exceed LINK_MAX.
pathname was too long.
A directory component in pathname does not exist or is a dangling symbolic link.
Insufficient kernel memory was available.
The device containing pathname has no room for the new directory.
The new directory cannot be created because the user's disk quota is exhausted.
A component used as a directory in pathname is not, in fact, a directory.
(mkdirat()) pathname is relative and dirfd is a file descriptor referring to a file other than a directory.
The filesystem containing pathname does not support the creation of directories.
pathname refers to a file on a read-only filesystem.


Under Linux, apart from the permission bits, the S_ISVTX mode bit is also honored.

glibc notes

On older kernels where mkdirat() is unavailable, the glibc wrapper function falls back to the use of mkdir(). When pathname is a relative pathname, glibc constructs a pathname based on the symbolic link in /proc/self/fd that corresponds to the dirfd argument.




SVr4, BSD, POSIX.1-2001.
Linux 2.6.16, glibc 2.4.


There are many infelicities in the protocol underlying NFS. Some of these affect mkdir().


mkdir(1), chmod(2), chown(2), mknod(2), mount(2), rmdir(2), stat(2), umask(2), unlink(2), acl(5), path_resolution(7)

2024-05-02 Linux man-pages (unreleased)