1 .\" Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
13 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
14 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
17 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 .Nd "library for PID files handling"
42 .Fn pidfile_open "const char *path" "mode_t mode" "pid_t *pidptr"
44 .Fn pidfile_write "struct pidfh *pfh"
46 .Fn pidfile_close "struct pidfh *pfh"
48 .Fn pidfile_remove "struct pidfh *pfh"
50 .Fn pidfile_fileno "struct pidfh *pfh"
54 family of functions allows daemons to handle PID files.
57 to lock a pidfile and detect already running daemons.
61 function opens (or creates) a file specified by the
63 argument and locks it.
64 If a file can not be locked, a PID of an already running daemon is returned in
67 argument (if it is not
69 The function does not write process' PID into the file here, so it can be
72 and exit with a proper error message when needed.
77 .Pa /var/run/ Ns Ao Va progname Ac Ns Pa .pid
82 function writes process' PID into a previously opened file.
86 function closes a pidfile.
87 It should be used after daemon
89 to start a child process.
93 function closes and removes a pidfile.
97 function returns the file descriptor for the open pid file.
101 function returns a valid pointer to a
103 structure on success, or
110 .Rv -std pidfile_write pidfile_close pidfile_remove
114 function returns the low-level file descriptor.
115 It returns -1 and sets
119 is specified, or if the pidfile is no longer open.
121 The following example shows in which order these functions should be used.
122 Note that it is safe to pass
133 pid_t otherpid, childpid;
135 pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid);
137 if (errno == EEXIST) {
138 errx(EXIT_FAILURE, "Daemon already running, pid: %jd.",
141 /* If we cannot create pidfile from other reasons, only warn. */
142 warn("Cannot open or create pidfile");
145 if (daemon(0, 0) == -1) {
146 warn("Cannot daemonize");
158 syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
165 syslog(LOG_INFO, "Child %jd started.", (intmax_t)childpid);
176 function will fail if:
179 Some process already holds the lock on the given pidfile, meaning that a
180 daemon is already running.
181 .It Bq Er ENAMETOOLONG
182 Specified pidfile's name is too long.
184 Some process already holds the lock on the given pidfile, but PID read
185 from there is invalid.
187 Some process already holds the lock on the given pidfile, but the file
189 Most likely, the existing daemon is writing new PID into
195 function may also fail and set
197 for any errors specified for the
206 function will fail if:
209 Improper function use.
210 Probably called before
216 function may also fail and set
218 for any errors specified for the
227 function may fail and set
229 for any errors specified for the
237 function will fail if:
240 Improper function use.
241 Probably called not from the process which made
247 function may also fail and set
249 for any errors specified for the
261 function will fail if:
264 Improper function use.
265 Probably called not from the process which used
276 functionality is based on ideas from
277 .An John-Mark Gurney Aq jmg@FreeBSD.org .
279 The code and manual page was written by
280 .An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .