|File: [cvs.NetBSD.org] / src / lib / libc / gen / daemon.3 (download)
Revision 1.13, Tue Oct 1 16:07:01 2002 UTC (16 years, 2 months ago) by wiz
CVS Tags: nathanw_sa_before_merge, nathanw_sa_base, fvdl_fs64_base
Changes since 1.12: +8 -10
New sentence, new line; -1 -> \-1; simplify mdoc in one place.
.\" $NetBSD: daemon.3,v 1.13 2002/10/01 16:07:01 wiz Exp $
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.\" @(#)daemon.3 8.1 (Berkeley) 6/9/93
.Dd September 3, 1999
.Dt DAEMON 3
.Nd run in the background
.Fd #include \*[Lt]stdlib.h\*[Gt]
.Fn daemon "int nochdir" "int noclose"
function is for programs wishing to detach themselves from the
controlling terminal and run in the background as system daemons.
Unless the argument
changes the current working directory to the root
.Pq Pa / .
Unless the argument
will redirect standard input, standard output and standard error
.Pa /dev/null .
.Sh RETURN VALUES
On return 0 indicates success with \-1 indicating error.
may fail and set
for any of the errors specified for the library functions
.Xr fork 2
.Xr setsid 2 .
.Sh SEE ALSO
.Xr fork 2 ,
.Xr setsid 2
function first appeared in
.Bx 4.4 .
argument is non-zero,
will close the first three file descriptors and redirect them to
.Pa /dev/null .
Normally, these correspond to standard input, standard output and
However, if any of those file descriptors refer to something else they
will still be closed, resulting in incorrect behavior of the calling program.
This can happen if any of standard input, standard output or standard error
have been closed before the program was run.
should therefore make sure to either call
before opening any files or sockets or, alternately, verifying that
any file descriptors obtained have a value greater than 2.
as part of its tty detachment mechanism.
Consequently the process id changes when
can not be reliably waited upon until
has been invoked.