man1/mknod.1

   1 .\" Copyright Andries Brouwer, Ragnar Hojland Espinosa and A. Wik, 1998.
   2 .\"
   3 .\" This file may be copied under the conditions described
   4 .\" in the LDP GENERAL PUBLIC LICENSE, Version 1, September 1998
   5 .\" that should have been distributed together with this file.
   6 .\"
   7 .TH MKNOD 1 1998-11 "GNU fileutils 4.0"
   8 .SH NAME
   9 mknod \- make block or character special files
  10 .SH SYNOPSIS
  11 .BI "mknod [" options "] " name " {bc} " "major minor"
  12 .br
  13 .BI "mknod [" options "] " name " p"
  14 .sp
  15 GNU options (shortest form):
  16 .BI "[\-m " mode "] [\-\-help] [\-\-version] [\-\-]"
  17 .SH DESCRIPTION
  18 .B mknod
  19 creates a FIFO (named pipe), character special file, or block special
  20 file with the specified
  21 .IR name .
  22 .PP
  23 A special file is a triple (boolean, integer, integer)
  24 stored in the filesystem.
  25 The boolean chooses between character special file and
  26 block special file. The two integers are the major and minor
  27 device number.
  28 .PP
  29 Thus, a special file takes almost no place on disk, and is used
  30 only for communication with the operating system, not for data
  31 storage. Often special files refer to hardware devices (disk, tape, tty,
  32 printer) or to operating system services (/dev/null, /dev/random).
  33 .PP
  34 Block special files usually are disk-like devices
  35 (where data can be accessed given a block number,
  36 and e.g. it is meaningful to have a block cache).
  37 All other devices are character special files.
  38 (Long ago the distinction was a different one: I/O to
  39 a character special file would be unbuffered, to a block
  40 special file buffered.)
  41 .PP
  42 The
  43 .B mknod
  44 command is what creates files of this type.
  45 .PP
  46 The argument following
  47 .I name
  48 specifies the type of file to make:
  49 .RS
  50 .TP
  51 .B p
  52 for a FIFO
  53 .TP
  54 .B b
  55 for a block (buffered) special file
  56 .TP
  57 .B c
  58 for a character (unbuffered) special file
  59 .RE
  60 .PP
  61 The GNU version of
  62 .B mknod
  63 allows
  64 .B u
  65 (`unbuffered') as a synonym for
  66 .BR c .
  67 .PP
  68 When making a block or character special file, the major and minor
  69 device numbers must be given after the file type (in decimal, or
  70 in octal with leading 0; the GNU version also allows hexadecimal
  71 with leading 0x).
  72 By default, the mode of created files is 0666 (`a+rw') minus the bits
  73 set in the umask.
  74 .SH OPTIONS
  75 .TP
  76 .BI "\-m " mode ", \-\-mode=" mode
  77 Set the mode of created files to
  78 .IR mode ,
  79 which can be symbolic as in
  80 .BR chmod (1)
  81 and then uses the default mode as the point of departure.
  82 .SH "GNU STANDARD OPTIONS"
  83 .TP
  84 .B "\-\-help"
  85 Print a usage message on standard output and exit successfully.
  86 .TP
  87 .B "\-\-version"
  88 Print version information on standard output, then exit successfully.
  89 .TP
  90 .B "\-\-"
  91 Terminate option list.
  92 .SH "CONFORMING TO"
  93 POSIX does not describe this command as it is nonportable,
  94 and recommends using
  95 .BR mkfifo (1)
  96 to make FIFOs.
  97 SVID has a command
  98 .I /etc/mknod
  99 with the above syntax, but without the mode option.
 100 .SH NOTES
 101 On a Linux system (version 1.3.22 or newer) the file
 102 .I /usr/src/linux/Documentation/devices.tex
 103 contains a list of devices with device name, type, major and minor number.
 104 .LP
 105 The present page describes
 106 .B mknod
 107 as found in the fileutils-4.0 package;
 108 other versions may differ slightly.
 109 .SH "SEE ALSO"
 110 .BR chmod (1),
 111 .BR mkfifo (1),
 112 .BR mknod (2)