man2/mkdir.2

.\" This manpage is Copyright (C) 1992 Drew Eckhardt;
.\"             and Copyright (C) 1993 Michael Haardt
.\"             and Copyright (C) 1993,1994 Ian Jackson
.\"		and Copyright (C) 2006, 2014 Michael Kerrisk
.\"
.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
.\" You may distribute it under the terms of the GNU General
.\" Public License. It comes with NO WARRANTY.
.\" %%%LICENSE_END
.\"
.TH MKDIR 2 2021-03-22 "Linux" "Linux Programmer's Manual"
.SH NAME
mkdir, mkdirat \- create a directory
.SH SYNOPSIS
.nf
.B #include <sys/stat.h>
.\" .B #include <unistd.h>
.PP
.BI "int mkdir(const char *" pathname ", mode_t " mode );
.PP
.BR "#include <fcntl.h>           " "/* Definition of AT_* constants */"
.B #include <sys/stat.h>
.PP
.BI "int mkdirat(int " dirfd ", const char *" pathname ", mode_t " mode );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR mkdirat ():
.nf
    Since glibc 2.10:
        _POSIX_C_SOURCE >= 200809L
    Before glibc 2.10:
        _ATFILE_SOURCE
.fi
.SH DESCRIPTION
.BR mkdir ()
attempts to create a directory named
.IR pathname .
.PP
The argument
.I mode
specifies the mode for the new directory (see
.BR inode (7)).
It is modified by the process's
.I umask
in the usual way: in the absence of a default ACL, the mode of the
created directory is
.RI ( mode " & \(ti" umask " & 0777)."
Whether other
.I mode
bits are honored for the created directory depends on the operating system.
For Linux, see NOTES below.
.PP
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
.RI ( "mount \-o bsdgroups"
or, synonymously
.IR "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.
.PP
If the parent directory has the set-group-ID bit set, then so will the
newly created directory.
.\"
.\"
.SS mkdirat()
The
.BR mkdirat ()
system call operates in exactly the same way as
.BR mkdir (),
except for the differences described here.
.PP
If the pathname given in
.I pathname
is relative, then it is interpreted relative to the directory
referred to by the file descriptor
.I dirfd
(rather than relative to the current working directory of
the calling process, as is done by
.BR mkdir ()
for a relative pathname).
.PP
If
.I pathname
is relative and
.I dirfd
is the special value
.BR AT_FDCWD ,
then
.I pathname
is interpreted relative to the current working
directory of the calling process (like
.BR mkdir ()).
.PP
If
.I pathname
is absolute, then
.I dirfd
is ignored.
.PP
See
.BR openat (2)
for an explanation of the need for
.BR mkdirat ().
.SH RETURN VALUE
.BR mkdir ()
and
.BR mkdirat ()
return zero on success.
On error, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EACCES
The parent directory does not allow write permission to the process,
or one of the directories in
.I pathname
did not allow search permission.
(See also
.BR path_resolution (7).)
.TP
.B EDQUOT
The user's quota of disk blocks or inodes on the filesystem has been
exhausted.
.TP
.B EEXIST
.I pathname
already exists (not necessarily as a directory).
This includes the case where
.I pathname
is a symbolic link, dangling or not.
.TP
.B EFAULT
.IR pathname " points outside your accessible address space."
.TP
.B EINVAL
The final component ("basename") of the new directory's
.I pathname
is invalid
(e.g., it contains characters not permitted by the underlying filesystem).
.TP
.B ELOOP
Too many symbolic links were encountered in resolving
.IR pathname .
.TP
.B EMLINK
The number of links to the parent directory would exceed
.BR LINK_MAX .
.TP
.B ENAMETOOLONG
.IR pathname " was too long."
.TP
.B ENOENT
A directory component in
.I pathname
does not exist or is a dangling symbolic link.
.TP
.B ENOMEM
Insufficient kernel memory was available.
.TP
.B ENOSPC
The device containing
.I pathname
has no room for the new directory.
.TP
.B ENOSPC
The new directory cannot be created because the user's disk quota is
exhausted.
.TP
.B ENOTDIR
A component used as a directory in
.I pathname
is not, in fact, a directory.
.TP
.B EPERM
The filesystem containing
.I pathname
does not support the creation of directories.
.TP
.B EROFS
.I pathname
refers to a file on a read-only filesystem.
.PP
The following additional errors can occur for
.BR mkdirat ():
.TP
.B EBADF
.I dirfd
is not a valid file descriptor.
.TP
.B ENOTDIR
.I pathname
is relative and
.I dirfd
is a file descriptor referring to a file other than a directory.
.SH VERSIONS
.BR mkdirat ()
was added to Linux in kernel 2.6.16;
library support was added to glibc in version 2.4.
.SH CONFORMING TO
.BR mkdir ():
SVr4, BSD, POSIX.1-2001, POSIX.1-2008.
.\" SVr4 documents additional EIO, EMULTIHOP
.PP
.BR mkdirat ():
POSIX.1-2008.
.SH NOTES
Under Linux, apart from the permission bits, the
.B S_ISVTX
.I mode
bit is also honored.
.PP
There are many infelicities in the protocol underlying NFS.
Some of these affect
.BR mkdir ().
.SS Glibc notes
On older kernels where
.BR mkdirat ()
is unavailable, the glibc wrapper function falls back to the use of
.BR mkdir ().
When
.I pathname
is a relative pathname,
glibc constructs a pathname based on the symbolic link in
.IR /proc/self/fd
that corresponds to the
.IR dirfd
argument.
.SH SEE ALSO
.BR mkdir (1),
.BR chmod (2),
.BR chown (2),
.BR mknod (2),
.BR mount (2),
.BR rmdir (2),
.BR stat (2),
.BR umask (2),
.BR unlink (2),
.BR acl (5),
.BR path_resolution (7)