.\" 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

.\"

.\" Modified 1996-08-18 by urs

.\" Modified 2003-04-23 by Michael Kerrisk

.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>

.\"

.TH MKNOD 2 2017-09-15 "Linux" "Linux Programmer's Manual"

.SH NAME

mknod, mknodat \- create a special or ordinary file

.SH SYNOPSIS

.nf

.B #include <sys/types.h>

.B #include <sys/stat.h>

.B #include <fcntl.h>

.B #include <unistd.h>

.PP

.BI "int mknod(const char *" pathname ", mode_t " mode ", dev_t " dev );

.BR "#include <fcntl.h>           " "/* Definition of AT_* constants */"

.B #include <sys/stat.h>

.PP

.BI "int mknodat(int " dirfd ", const char *" pathname ", mode_t " mode \

", dev_t " dev );

.fi

.PP

.in -4n

Feature Test Macro Requirements for glibc (see

.BR feature_test_macros (7)):

.in

.PP

.BR mknod ():

.ad l

.RS 4

_XOPEN_SOURCE\ >=\ 500

.\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED

    || /* Since glibc 2.19: */ _DEFAULT_SOURCE

    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

.RE

.ad

.SH DESCRIPTION

The system call

.BR mknod ()

creates a filesystem node (file, device special file, or

named pipe) named

.IR pathname ,

with attributes specified by

.I mode

and

.IR dev .

.PP

The

.I mode

argument specifies both the file mode to use and the type of node

to be created.

It should be a combination (using bitwise OR) of one of the file types

listed below and zero or more of the file mode bits listed in

.BR inode (7).

.PP

The file mode is modified by the process's

.I umask

in the usual way: in the absence of a default ACL, the permissions of the

created node are

.RI ( mode " & ~" umask ).

.PP

The file type must be one of

.BR S_IFREG ,

.BR S_IFCHR ,

.BR S_IFBLK ,

.BR S_IFIFO ,

or

.B S_IFSOCK

.\" (S_IFSOCK since Linux 1.2.4)

to specify a regular file (which will be created empty), character

special file, block special file, FIFO (named pipe), or UNIX domain socket,

respectively.

(Zero file type is equivalent to type

.BR S_IFREG .)

.PP

If the file type is

.B S_IFCHR

or

.BR S_IFBLK ,

then

.I dev

specifies the major and minor numbers of the newly created device

special file

.RB ( makedev (3)

may be useful to build the value for

.IR dev );

otherwise it is ignored.

.PP

If

.I pathname

already exists, or is a symbolic link, this call fails with an

.B EEXIST

error.

.PP

The newly created node will be owned by the effective user ID of the

process.

If the directory containing the node has the set-group-ID

bit set, or if the filesystem is mounted with BSD group semantics, the

new node will inherit the group ownership from its parent directory;

otherwise it will be owned by the effective group ID of the process.

.\"

.\"

.SS mknodat()

The

.BR mknodat ()

system call operates in exactly the same way as

.BR mknod (),

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 mknod ()

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 mknod ()).

.PP

If

.I pathname

is absolute, then

.I dirfd

is ignored.

.PP

See

.BR openat (2)

for an explanation of the need for

.BR mknodat ().

.SH RETURN VALUE

.BR mknod ()

and

.BR mknodat ()

return zero on success, or \-1 if an error occurred (in which case,

.I errno

is set appropriately).

.SH ERRORS

.TP

.B EACCES

The parent directory does not allow write permission to the process,

or one of the directories in the path prefix of

.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.

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

.I mode

requested creation of something other than a regular file, device

special file, FIFO or socket.

.TP

.B ELOOP

Too many symbolic links were encountered in resolving

.IR pathname .

.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 node.

.TP

.B ENOTDIR

A component used as a directory in

.I pathname

is not, in fact, a directory.

.TP

.B EPERM

.I mode

requested creation of something other than a regular file,

FIFO (named pipe), or UNIX domain socket, and the caller

is not privileged (Linux: does not have the

.B CAP_MKNOD

capability);

.\" For UNIX domain sockets and regular files, EPERM is returned only in

.\" Linux 2.2 and earlier; in Linux 2.4 and later, unprivileged can

.\" use mknod() to make these files.

also returned if the filesystem containing

.I pathname

does not support the type of node requested.

.TP

.B EROFS

.I pathname

refers to a file on a read-only filesystem.

.PP

The following additional errors can occur for

.BR mknodat ():

.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 mknodat ()

was added to Linux in kernel 2.6.16;

library support was added to glibc in version 2.4.

.SH CONFORMING TO

.BR mknod ():

SVr4, 4.4BSD, POSIX.1-2001 (but see below), POSIX.1-2008.

.\" The Linux version differs from the SVr4 version in that it

.\" does not require root permission to create pipes, also in that no

.\" EMULTIHOP, ENOLINK, or EINTR error is documented.

.PP

.BR mknodat ():

POSIX.1-2008.

.SH NOTES

POSIX.1-2001 says: "The only portable use of

.BR mknod ()

is to create a FIFO-special file.

If

.I mode

is not

.B S_IFIFO

or

.I dev

is not 0, the behavior of

.BR mknod ()

is unspecified."

However, nowadays one should never use

.BR mknod ()

for this purpose; one should use

.BR mkfifo (3),

a function especially defined for this purpose.

.PP

Under Linux,

.BR mknod ()

cannot be used to create directories.

One should make directories with

.BR mkdir (2).

.\" and one should make UNIX domain sockets with socket(2) and bind(2).

.PP

There are many infelicities in the protocol underlying NFS.

Some of these affect

.BR mknod ()

and

.BR mknodat ().

.SH SEE ALSO

.BR mknod (1),

.BR chmod (2),

.BR chown (2),

.BR fcntl (2),

.BR mkdir (2),

.BR mount (2),

.BR socket (2),

.BR stat (2),

.BR umask (2),

.BR unlink (2),

.BR makedev (3),

.BR mkfifo (3),

.BR acl (5)

.BR path_resolution (7)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.