mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-29 12:03:03 +00:00
113 lines
3.4 KiB
Groff
113 lines
3.4 KiB
Groff
.\" Copyright (c) 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)daemon.3 8.1 (Berkeley) 6/9/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd June 9, 1993
|
|
.Dt DAEMON 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm daemon
|
|
.Nd run in the background
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In stdlib.h
|
|
.Ft int
|
|
.Fn daemon "int nochdir" "int noclose"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn daemon
|
|
function is for programs wishing to detach themselves from the
|
|
controlling terminal and run in the background as system daemons.
|
|
.Pp
|
|
Unless the argument
|
|
.Fa nochdir
|
|
is non-zero,
|
|
.Fn daemon
|
|
changes the current working directory to the root
|
|
.Pq Pa / .
|
|
.Pp
|
|
Unless the argument
|
|
.Fa noclose
|
|
is non-zero,
|
|
.Fn daemon
|
|
will redirect standard input, standard output, and standard error to
|
|
.Pa /dev/null .
|
|
.Sh RETURN VALUES
|
|
.Rv -std daemon
|
|
.Sh ERRORS
|
|
The
|
|
.Fn daemon
|
|
function may fail and set
|
|
.Va errno
|
|
for any of the errors specified for the library functions
|
|
.Xr fork 2
|
|
and
|
|
.Xr setsid 2 .
|
|
.Sh SEE ALSO
|
|
.Xr fork 2 ,
|
|
.Xr setsid 2 ,
|
|
.Xr sigaction 2
|
|
.Sh HISTORY
|
|
The
|
|
.Fn daemon
|
|
function first appeared in
|
|
.Bx 4.4 .
|
|
.Sh CAVEATS
|
|
Unless the
|
|
.Fa noclose
|
|
argument is non-zero,
|
|
.Fn daemon
|
|
will close the first three file descriptors and redirect them to
|
|
.Pa /dev/null .
|
|
Normally, these correspond to standard input, standard output, and
|
|
standard error.
|
|
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.
|
|
Programs using
|
|
.Fn daemon
|
|
should therefore either call
|
|
.Fn daemon
|
|
before opening any files or sockets, or verify that any file
|
|
descriptors obtained have values greater than 2.
|
|
.Pp
|
|
The
|
|
.Fn daemon
|
|
function temporarily ignores
|
|
.Dv SIGHUP
|
|
while calling
|
|
.Xr setsid 2
|
|
to prevent a parent session group leader's calls to
|
|
.Xr fork 2
|
|
and then
|
|
.Xr _exit 2
|
|
from prematurely terminating the child process.
|