.\"	$OpenBSD: mkdir.2,v 1.18 2017/03/23 18:40:01 millert Exp $
.\"	$NetBSD: mkdir.2,v 1.8 1995/02/27 12:34:22 cgd Exp $
.\"
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.\"     @(#)mkdir.2	8.2 (Berkeley) 12/11/93
.\"
.Dd $Mdocdate: March 23 2017 $
.Dt MKDIR 2
.Os
.Sh NAME
.Nm mkdir ,
.Nm mkdirat
.Nd make a directory file
.Sh SYNOPSIS
.In sys/stat.h
.Ft int
.Fn mkdir "const char *path" "mode_t mode"
.In sys/stat.h
.In fcntl.h
.Ft int
.Fn mkdirat "int fd" "const char *path" "mode_t mode"
.Sh DESCRIPTION
The directory
.Fa path
is created with the access permissions specified by
.Fa mode
and restricted by the
.Xr umask 2
of the calling process.
.Pp
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 is created.
.Pp
The
.Fn mkdirat
function is equivalent to
.Fn mkdir
except that where
.Fa path
specifies a relative path,
the newly created directory is created relative to
the directory associated with file descriptor
.Fa fd
instead of the current working directory.
.Pp
If
.Fn mkdirat
is passed the special value
.Dv AT_FDCWD
(defined in
.In fcntl.h )
in the
.Fa fd
parameter, the current working directory is used
and the behavior is identical to a call to
.Fn mkdir .
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
.Fn mkdir
and
.Fn mkdirat
will fail and no directory will be created if:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded
.Dv NAME_MAX
characters, or an entire pathname (including the terminating NUL)
exceeded
.Dv PATH_MAX
bytes.
.It Bq Er ENOENT
A component of the path prefix does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix,
or write permission is denied
on the parent directory of the directory to be created.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EROFS
The named file resides on a read-only file system.
.It Bq Er EEXIST
The named file exists.
.It Bq Er ENOSPC
The new directory cannot be created because there is no space left
on the file system that will contain the directory.
.It Bq Er ENOSPC
There are no free inodes on the file system on which the
directory is being created.
.It Bq Er EDQUOT
The new directory cannot be created because the user's
quota of disk blocks on the file system that will
contain the directory has been exhausted.
.It Bq Er EDQUOT
The user's quota of inodes on the file system on
which the directory is being created has been exhausted.
.It Bq Er EIO
An I/O error occurred while making the directory entry or allocating the inode.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.It Bq Er EFAULT
.Fa path
points outside the process's allocated address space.
.El
.Pp
Additionally,
.Fn mkdirat
will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa path
argument specifies a relative path and the
.Fa fd
argument is neither
.Dv AT_FDCWD
nor a valid file descriptor.
.It Bq Er ENOTDIR
The
.Fa path
argument specifies a relative path and the
.Fa fd
argument is a valid file descriptor but it does not reference a directory.
.It Bq Er EACCES
The
.Fa path
argument specifies a relative path but search permission is denied
for the directory which the
.Fa fd
file descriptor references.
.El
.Sh SEE ALSO
.Xr chmod 2 ,
.Xr stat 2 ,
.Xr umask 2
.Sh STANDARDS
The
.Fn mkdir
and
.Fn mkdirat
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
A
.Fn mkdir
system call first appeared in
.At v1 .
It was renamed to
.Fn makdir
in
.At v2 .
However, it did not exist from
.At v4
to
.Bx 4.1 ;
in those releases,
.Xr mknod 2
had to be used.
Since
.Fn mkdir
reappeared in
.Bx 4.1c ,
it no longer requires superuser privileges and it automatically creates the
.Sq \&.
and
.Sq \&..
directory entries.
.Pp
The
.Fn mkdirat
system call has been available since
.Ox 5.0 .