.\" Copyright Andries Brouwer, Ragnar Hojland Espinosa and A. Wik, 1998.
.\"
.\" This file may be copied under the conditions described
.\" in the LDP GENERAL PUBLIC LICENSE, Version 1, September 1998
.\" that should have been distributed together with this file.
.\"
.TH MKNOD 1 1998-11 "GNU fileutils 4.0"
.SH NAME
mknod \- make block or character special files
.SH SYNOPSIS
.BI "mknod [" options "] " name " {bc} " "major minor"
.br
.BI "mknod [" options "] " name " p"
.sp
GNU options (shortest form):
.BI "[\-m " mode "] [\-\-help] [\-\-version] [\-\-]"
.SH DESCRIPTION
.B mknod
creates a FIFO (named pipe), character special file, or block special
file with the specified
.IR name .
.PP
A special file is a triple (boolean, integer, integer)
stored in the filesystem.
The boolean chooses between character special file and
block special file. The two integers are the major and minor
device number.
.PP
Thus, a special file takes almost no place on disk, and is used
only for communication with the operating system, not for data
storage. Often special files refer to hardware devices (disk, tape, tty,
printer) or to operating system services (/dev/null, /dev/random).
.PP
Block special files usually are disk-like devices
(where data can be accessed given a block number,
and e.g. it is meaningful to have a block cache).
All other devices are character special files.
(Long ago the distinction was a different one: I/O to
a character special file would be unbuffered, to a block
special file buffered.)
.PP
The
.B mknod
command is what creates files of this type.
.PP
The argument following
.I name
specifies the type of file to make:
.RS
.TP
.B p
for a FIFO
.TP
.B b
for a block (buffered) special file
.TP
.B c
for a character (unbuffered) special file
.RE
.PP
The GNU version of
.B mknod
allows
.B u
(`unbuffered') as a synonym for
.BR c .
.PP
When making a block or character special file, the major and minor
device numbers must be given after the file type (in decimal, or
in octal with leading 0; the GNU version also allows hexadecimal
with leading 0x).
By default, the mode of created files is 0666 (`a+rw') minus the bits
set in the umask.
.SH OPTIONS
.TP
.BI "\-m " mode ", \-\-mode=" mode
Set the mode of created files to
.IR mode ,
which can be symbolic as in
.BR chmod (1)
and then uses the default mode as the point of departure.
.SH "GNU STANDARD OPTIONS"
.TP
.B "\-\-help"
Print a usage message on standard output and exit successfully.
.TP
.B "\-\-version"
Print version information on standard output, then exit successfully.
.TP
.B "\-\-"
Terminate option list.
.SH "CONFORMING TO"
POSIX does not describe this command as it is nonportable,
and recommends using
.BR mkfifo (1)
to make FIFOs.
SVID has a command
.I /etc/mknod
with the above syntax, but without the mode option.
.SH NOTES
On a Linux system (version 1.3.22 or newer) the file
.I /usr/src/linux/Documentation/devices.txt
contains a list of devices with device name, type, major and minor number.
.LP
The present page describes
.B mknod
as found in the fileutils-4.0 package;
other versions may differ slightly.
.SH "SEE ALSO"
.BR chmod (1),
.BR mkfifo (1),
.BR mknod (2)