minix/lib/libutil/pidfile.3

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.\" $NetBSD: pidfile.3,v 1.12 2010/05/05 22:05:31 wiz Exp $
.\"
.\" Copyright (c) 1999 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Jason R. Thorpe.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" 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
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.Dd May 4, 2010
.Dt PIDFILE 3
.Os
.Sh NAME
.Nm pidfile
.Nd write a daemon pid file
.Sh LIBRARY
.Lb libutil
.Sh SYNOPSIS
.In util.h
.Ft int
.Fn pidfile "const char *basename"
.Sh DESCRIPTION
.Fn pidfile
writes a file containing the process ID of the program to the
.Pa /var/run
directory.
The file name has the form
.Pa /var/run/basename.pid .
If the
.Ar basename
argument is
.Dv NULL ,
.Fn pidfile
will determine the program name and use that instead.
.Pp
The pid file can be used as a quick reference if
the process needs to be sent a signal.
When the program exits, the pid file will be removed automatically, unless
the program receives a fatal signal.
.Pp
Note that only the first invocation of
.Fn pidfile
causes a pid file to be written; subsequent invocations have no effect
unless a new
.Ar basename
is supplied.
If called with a new
.Ar basename ,
.Fn pidfile
will remove the old pid file and write the new one.
.Sh RETURN VALUES
.Fn pidfile
returns 0 on success and -1 on failure.
.Sh SEE ALSO
.Xr atexit 3
.Sh HISTORY
The
.Fn pidfile
function call appeared in
.Nx 1.5 .
.Sh BUGS
.Fn pidfile
uses
.Xr atexit 3
to ensure the pidfile is unlinked at program exit.
However, programs that use the
.Xr _exit 2
function (for example, in signal handlers)
will not trigger this behaviour.