man4/null.4

.\" Copyright (c) 1993 Michael Haardt (michael@moria.de),
.\"     Fri Apr  2 11:32:09 MET DST 1993
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.\" Modified Sat Jul 24 17:00:12 1993 by Rik Faith (faith@cs.unc.edu)
.TH NULL 4 2009-02-23 "Linux" "Linux Programmer's Manual"
.SH NAME
null, zero \- data sink
.SH DESCRIPTION
Data written to a \fBnull\fP or \fBzero\fP special file is discarded.
.PP
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).
.LP
\fBnull\fP and \fBzero\fP are typically created by:
.RS
.sp
mknod \-m 666 /dev/null c 1 3
.br
mknod \-m 666 /dev/zero c 1 5
.br
chown root:root /dev/null /dev/zero
.RE
.SH FILES
.I /dev/null
.br
.I /dev/zero
.SH NOTES
If these devices are not writable and readable for all users, many
programs will act strangely.
.SH "SEE ALSO"
.BR chown (1),
.BR mknod (1),
.BR full (4)