1.\" $OpenBSD: pidfile.3,v 1.7 2013/06/05 03:40:26 tedu Exp $ 2.\" $NetBSD: pidfile.3,v 1.2 2001/04/12 22:34:31 sommerfeld Exp $ 3.\" 4.\" Copyright (c) 1999 The NetBSD Foundation, Inc. 5.\" All rights reserved. 6.\" 7.\" This code is derived from software contributed to The NetBSD Foundation 8.\" by Jason R. Thorpe. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29.\" POSSIBILITY OF SUCH DAMAGE. 30.\" 31.Dd $Mdocdate: June 5 2013 $ 32.Dt PIDFILE 3 33.Os 34.Sh NAME 35.Nm pidfile 36.Nd write a daemon pid file 37.Sh SYNOPSIS 38.In util.h 39.Ft int 40.Fn pidfile "const char *basename" 41.Sh DESCRIPTION 42.Fn pidfile 43writes a file containing the process ID of the program to the 44.Pa /var/run 45directory. 46The file name has the form 47.Pa /var/run/basename.pid . 48If the 49.Ar basename 50argument is NULL, 51.Nm 52will determine the program name and use that instead. 53.Pp 54The pid file can be used as a quick reference if 55the process needs to be sent a signal. 56When the program exits, the pid file will be removed automatically, 57unless the program receives a fatal signal. 58.Sh RETURN VALUES 59.Fn pidfile 60returns 0 on success and -1 on failure. 61.Sh SEE ALSO 62.Xr atexit 3 63.Sh HISTORY 64The 65.Nm 66function call appeared in 67.Ox 3.0 . 68.Sh CAVEATS 69If 70.Fn pidfile 71is called multiple times with different 72.Ar basename , 73only the last pidfile will be removed upon exit. 74.Pp 75.Fn pidfile 76uses 77.Fn atexit 78to ensure the pidfile is unlinked at program exit. 79However, programs that use the 80.Fn _exit 81function (for example, in signal handlers) 82will not trigger this behaviour. 83