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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.
66 and file can not be locked, the function will use it to store a PID of an
67 already running daemon or
69 in case daemon did not write its PID yet.
70 The function does not write process' PID into the file here, so it can be
73 and exit with a proper error message when needed.
78 .Pa /var/run/ Ns Ao Va progname Ac Ns Pa .pid
83 function writes process' PID into a previously opened file.
87 function closes a pidfile.
88 It should be used after daemon
90 to start a child process.
94 function closes and removes a pidfile.
98 function returns a valid pointer to a
100 structure on success, or
107 .Rv -std pidfile_write pidfile_close pidfile_remove
109 The following example shows in which order these functions should be used.
110 Note that it is safe to pass
120 pid_t otherpid, childpid;
122 pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid);
124 if (errno == EEXIST) {
125 errx(EXIT_FAILURE, "Daemon already running, pid: %jd.",
128 /* If we cannot create pidfile from other reasons, only warn. */
129 warn("Cannot open or create pidfile");
132 if (daemon(0, 0) == -1) {
133 warn("Cannot daemonize");
145 syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
152 syslog(LOG_INFO, "Child %jd started.", (intmax_t)childpid);
163 function will fail if:
166 Some process already holds the lock on the given pidfile, meaning that a
167 daemon is already running.
172 the function will use it to store a PID of an already running daemon or
174 in case daemon did not write its PID yet.
175 .It Bq Er ENAMETOOLONG
176 Specified pidfile's name is too long.
178 Some process already holds the lock on the given pidfile, but PID read
179 from there is invalid.
184 function may also fail and set
186 for any errors specified for the
195 function will fail if:
198 Improper function use.
199 Probably called before
205 function may also fail and set
207 for any errors specified for the
216 function may fail and set
218 for any errors specified for the
226 function will fail if:
229 Improper function use.
230 Probably called not from the process which made
236 function may also fail and set
238 for any errors specified for the
255 functionality is based on ideas from
256 .An John-Mark Gurney Aq jmg@FreeBSD.org .
258 The code and manual page was written by
259 .An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .