mkdir(2)

NAME
mkdir, mkdirat - create a directory

LIBRARY
Standard C library (libc, -lc)

SYNOPSIS
#include <sys/stat.h>

int mkdir(const char *path, mode_t mode);

#include <fcntl.h>           /* Definition of AT_* constants */
#include <sys/stat.h>

int mkdirat(int dirfd, const char *path, mode_t mode);

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

mkdirat():
    Since glibc 2.10:
        _POSIX_C_SOURCE >= 200809L
    Before glibc 2.10:
        _ATFILE_SOURCE

DESCRIPTION
mkdir() attempts to create a directory named path.

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 VERSIONS 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.

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

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

If path is absolute, then dirfd is ignored.

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

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

ERRORS

EACCES
    The parent directory does not allow write permission to the process, or one of the directories in path did not allow search permission. (See also path_resolution(7).)

EBADF
    (mkdirat()) path is relative but dirfd is neither AT_FDCWD nor a valid file descriptor.

EDQUOT
    The user's quota of disk blocks or inodes on the filesystem has been exhausted.

EEXIST
    path already exists (not necessarily as a directory). This includes the case where path is a symbolic link, dangling or not.

EFAULT
    path points outside your accessible address space.

EINVAL
    The final component ("basename") of the new directory's path is invalid (e.g., it contains characters not permitted by the underlying filesystem).

ELOOP
    Too many symbolic links were encountered in resolving path.

EMLINK
    The number of links to the parent directory would exceed LINK_MAX.

ENAMETOOLONG
    path was too long.

ENOENT
    A directory component in path does not exist or is a dangling symbolic link.

ENOMEM
    Insufficient kernel memory was available.

ENOSPC
    The device containing path has no room for the new directory.

ENOSPC
    The new directory cannot be created because the user's disk quota is exhausted.

ENOTDIR
    A component used as a directory in path is not, in fact, a directory.

ENOTDIR
    (mkdirat()) path is relative and dirfd is a file descriptor referring to a file other than a directory.

EPERM
    The filesystem containing path does not support the creation of directories.

EROFS
    path refers to a file on a read-only filesystem.

EOVERFLOW
    UID or GID mappings (see user_namespaces(7)) have not been configured.

VERSIONS
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 path is relative, glibc constructs a pathname based on the symbolic link in /proc/self/fd that corresponds to the dirfd argument.

STANDARDS
POSIX.1-2024.

HISTORY

mkdir()
    SVr4, BSD, POSIX.1-2001.

mkdirat()
    POSIX.1-2008. Linux 2.6.16, glibc 2.4.

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

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