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 pidfile.
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.
121 is specified, or if the pidfile is no longer open.
123 The following example shows in which order these functions should be used.
124 Note that it is safe to pass
135 pid_t otherpid, childpid;
137 pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid);
139 if (errno == EEXIST) {
140 errx(EXIT_FAILURE, "Daemon already running, pid: %jd.",
143 /* If we cannot create pidfile from other reasons, only warn. */
144 warn("Cannot open or create pidfile");
147 if (daemon(0, 0) == -1) {
148 warn("Cannot daemonize");
160 syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
167 syslog(LOG_INFO, "Child %jd started.", (intmax_t)childpid);
178 function will fail if:
181 Some process already holds the lock on the given pidfile, meaning that a
182 daemon is already running.
183 .It Bq Er ENAMETOOLONG
184 Specified pidfile's name is too long.
186 Some process already holds the lock on the given pidfile, but PID read
187 from there is invalid.
189 Some process already holds the lock on the given pidfile, but the file
191 Most likely, the existing daemon is writing new PID into
197 function may also fail and set
199 for any errors specified for the
208 function will fail if:
211 Improper function use.
212 Probably called before
218 function may also fail and set
220 for any errors specified for the
229 function may fail and set
231 for any errors specified for the
239 function will fail if:
242 Improper function use.
243 Probably called not from the process which made
249 function may also fail and set
251 for any errors specified for the
263 function will fail if:
266 Improper function use.
267 Probably called not from the process which used
278 functionality is based on ideas from
279 .An John-Mark Gurney Aq jmg@FreeBSD.org .
281 The code and manual page was written by
282 .An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .