2008-07-06 15:10:32 +00:00
|
|
|
.\" Copyright (c) 1993 Michael Haardt (michael@moria.de),
|
|
|
|
.\" Fri Apr 2 11:32:09 MET DST 1993
|
2004-11-03 13:51:07 +00:00
|
|
|
.\"
|
|
|
|
.\" This is free documentation; you can redistribute it and/or
|
|
|
|
.\" modify it under the terms of the GNU General Public License as
|
|
|
|
.\" published by the Free Software Foundation; either version 2 of
|
|
|
|
.\" the License, or (at your option) any later version.
|
|
|
|
.\"
|
|
|
|
.\" The GNU General Public License's references to "object code"
|
|
|
|
.\" and "executables" are to be interpreted as the output of any
|
|
|
|
.\" document formatting or typesetting system, including
|
|
|
|
.\" intermediate and printed output.
|
|
|
|
.\"
|
|
|
|
.\" This manual is distributed in the hope that it will be useful,
|
|
|
|
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
|
|
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
|
|
.\" GNU General Public License for more details.
|
|
|
|
.\"
|
|
|
|
.\" You should have received a copy of the GNU General Public
|
|
|
|
.\" License along with this manual; if not, write to the Free
|
|
|
|
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
|
|
|
|
.\" USA.
|
2007-04-12 22:42:49 +00:00
|
|
|
.\"
|
2004-11-03 13:51:07 +00:00
|
|
|
.\" Modified Sat Jul 24 17:00:12 1993 by Rik Faith (faith@cs.unc.edu)
|
2009-02-23 02:39:15 +00:00
|
|
|
.TH NULL 4 2009-02-23 "Linux" "Linux Programmer's Manual"
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH NAME
|
|
|
|
null, zero \- data sink
|
|
|
|
.SH DESCRIPTION
|
2009-02-23 02:39:15 +00:00
|
|
|
Data written to a \fBnull\fP or \fBzero\fP special file is discarded.
|
2004-11-03 13:51:07 +00:00
|
|
|
.PP
|
2009-02-23 02:39:15 +00:00
|
|
|
Reads from the \fBnull\fP special file always return end of file (i.e.,
|
|
|
|
.BR read (2)
|
|
|
|
returns 0), whereas
|
|
|
|
reads from \fBzero\fP always return bytes containing zero (\e0 characters).
|
2004-11-03 13:51:07 +00:00
|
|
|
.LP
|
|
|
|
\fBnull\fP and \fBzero\fP are typically created by:
|
|
|
|
.RS
|
|
|
|
.sp
|
2005-07-06 07:41:37 +00:00
|
|
|
mknod \-m 666 /dev/null c 1 3
|
2004-11-03 13:51:07 +00:00
|
|
|
.br
|
2005-07-06 07:41:37 +00:00
|
|
|
mknod \-m 666 /dev/zero c 1 5
|
2004-11-03 13:51:07 +00:00
|
|
|
.br
|
2005-06-23 14:23:37 +00:00
|
|
|
chown root:root /dev/null /dev/zero
|
2004-11-03 13:51:07 +00:00
|
|
|
.RE
|
|
|
|
.SH FILES
|
|
|
|
.I /dev/null
|
|
|
|
.br
|
|
|
|
.I /dev/zero
|
2007-05-19 04:30:20 +00:00
|
|
|
.SH NOTES
|
|
|
|
If these devices are not writable and readable for all users, many
|
|
|
|
programs will act strangely.
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH "SEE ALSO"
|
|
|
|
.BR chown (1),
|
2006-05-29 04:42:08 +00:00
|
|
|
.BR mknod (1),
|
|
|
|
.BR full (4)
|