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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"
52 family of functions allows daemons to handle PID files.
55 to lock a pidfile and detect already running daemons.
59 function opens (or creates) a file specified by the
61 argument and locks it with the
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 a valid pointer to a
99 structure on success, or
105 .Rv -std pidfile_write pidfile_close pidfile_remove
107 The following example shows in which order these functions should be used.
108 Note that it is safe to pass
118 pid_t otherpid, childpid;
120 pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid);
122 if (errno == EEXIST) {
123 errx(EXIT_FAILURE, "Daemon already running, pid: %jd.",
126 /* If we cannot create pidfile from other reasons, only warn. */
127 warn("Cannot open or create pidfile");
130 if (daemon(0, 0) == -1) {
131 warn("Cannot daemonize");
143 syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
150 syslog(LOG_INFO, "Child %jd started.", (intmax_t)childpid);
161 function will fail if:
164 Some process already holds the lock on the given pidfile, meaning that a
165 daemon is already running.
166 .It Bq Er ENAMETOOLONG
167 Specified pidfile's name is too long.
169 Some process already holds the lock on the given pidfile, but PID read
170 from there is invalid.
172 Some process already holds the lock on the given pidfile, but the file
174 Most likely, the existing daemon is writing new PID into
180 function may also fail and set
182 for any errors specified for the
191 function will fail if:
194 Improper function use.
195 Probably called before
201 function may also fail and set
203 for any errors specified for the
212 function may fail and set
214 for any errors specified for the
222 function will fail if:
225 Improper function use.
226 Probably called not from the process which made
232 function may also fail and set
234 for any errors specified for the
250 functionality is based on ideas from
251 .An John-Mark Gurney Aq jmg@FreeBSD.org .
253 The code and manual page was written by
254 .An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .