MKDIR(2) BSD System Calls Manual MKDIR(2)
mkdir, mkdirat -- make a directory file
mkdir(const char *path, mode_t mode);
mkdirat(int fd, const char *path, mode_t mode);
The directory path is created with the access permissions specified by
mode and restricted by the umask(2) of the calling process.
The directory's owner ID is set to the process's effective user ID. The
directory's group ID is set to that of the parent directory in which it
The mkdirat() function is equivalent to mkdir() except that where path
specifies a relative path, the newly created directory is created rela-
tive to the directory associated with file descriptor fd instead of the
current working directory.
If mkdirat() is passed the special value AT_FDCWD (defined in <fcntl.h>)
in the fd parameter, the current working directory is used and the behav-
ior is identical to a call to mkdir().
Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
mkdir() and mkdirat() will fail and no directory will be created if:
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG] A component of a pathname exceeded NAME_MAX charac-
ters, or an entire pathname (including the terminating
NUL) exceeded PATH_MAX bytes.
[ENOENT] A component of the path prefix does not exist.
[EACCES] Search permission is denied for a component of the
[ELOOP] Too many symbolic links were encountered in translat-
ing the pathname.
[EROFS] The named file resides on a read-only file system.
[EEXIST] The named file exists.
[ENOSPC] The new directory cannot be created because there is
no space left on the file system that will contain the
[ENOSPC] There are no free inodes on the file system on which
the directory is being created.
[EDQUOT] The new directory cannot be created because the user's
quota of disk blocks on the file system that will con-
tain the directory has been exhausted.
[EDQUOT] The user's quota of inodes on the file system on which
the directory is being created has been exhausted.
[EIO] An I/O error occurred while making the directory entry
or allocating the inode.
[EIO] An I/O error occurred while reading from or writing to
the file system.
[EFAULT] path points outside the process's allocated address
Additionally, mkdirat() will fail if:
[EBADF] The path argument specifies a relative path and the fd
argument is neither AT_FDCWD nor a valid file descrip-
[ENOTDIR] The path argument specifies a relative path and the fd
argument is a valid file descriptor but it does not
reference a directory.
[EACCES] The path argument specifies a relative path but search
permission is denied for the directory which the fd
file descriptor references.
chmod(2), stat(2), umask(2)
The mkdir() and mkdirat() functions conform to IEEE Std 1003.1-2008
A mkdir() system call first appeared in Version 1 AT&T UNIX. It was
renamed to makdir() in Version 2 AT&T UNIX. However, it did not exist
from Version 4 AT&T UNIX to 4.1BSD; in those releases, mknod(2) had to be
used. Since mkdir() reappeared in 4.1cBSD, it no longer requires supe-
ruser privileges and it automatically creates the '.' and '..' directory
The mkdirat() system call has been available since OpenBSD 5.0.
BSD January 19, 2015 BSD