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.\"	@(#)daemon.3	8.1 (Berkeley) 6/9/93
.\" Added mentioning of glibc weirdness wrt unistd.h. 5/11/98, Al Viro
.TH DAEMON 3 2013-10-28 "GNU" "Linux Programmer's Manual"
.SH NAME
daemon \- run in the background
.SH SYNOPSIS
.B #include <unistd.h>
.sp
.BI "int daemon(int " nochdir ", int " noclose );
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR daemon ():
_BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE\ <\ 500)
.SH DESCRIPTION
The
.BR daemon ()
function is for programs wishing to detach themselves from the
controlling terminal and run in the background as system daemons.
.PP
If
.I nochdir
is zero,
.BR daemon ()
changes the calling process's current working directory
to the root directory ("/");
otherwise, the current working directory is left unchanged.
.PP
If
.I noclose
is zero,
.BR daemon ()
redirects standard input, standard output and standard error
to
.IR /dev/null ;
otherwise, no changes are made to these file descriptors.
.SH RETURN VALUE
(This function forks, and if the
.BR fork (2)
succeeds, the parent calls
.\" not .IR in order not to underline _
.BR _exit (2),
so that further errors are seen by the child only.)
On success
.BR daemon ()
returns zero.
If an error occurs,
.BR daemon ()
returns \-1 and sets
.I errno
to any of the errors specified for the
.BR fork (2)
and
.BR setsid (2).
.SH ATTRIBUTES
.SS Multithreading (see pthreads(7))
The
.BR daemon ()
function is thread-safe.
.SH CONFORMING TO
Not in POSIX.1-2001.
A similar function appears on the BSDs.
The
.BR daemon ()
function first appeared in 4.4BSD.
.SH NOTES
The glibc implementation can also return \-1 when
.I /dev/null
exists but is not a character device with the expected
major and minor numbers.
In this case,
.I errno
need not be set.
.SH SEE ALSO
.BR fork (2),
.BR setsid (2)
.SH COLOPHON
This page is part of release 3.74 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
\%http://www.kernel.org/doc/man\-pages/.