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35 .Nd "library for PID files handling"
41 .Fn pidfile_open "const char *path" "mode_t mode" "pid_t *pidptr"
43 .Fn pidfile_write "struct pidfh *pfh"
45 .Fn pidfile_close "struct pidfh *pfh"
47 .Fn pidfile_remove "struct pidfh *pfh"
49 .Fn pidfile_fileno "struct pidfh *pfh"
53 family of functions allows daemons to handle PID files.
56 to lock a pidfile and detect already running daemons.
60 function opens (or creates) a file specified by the
62 argument and locks it.
67 and file can not be locked, the function will use it to store a PID of an
68 already running daemon or
70 in case daemon did not write its PID yet.
71 The function does not write process' PID into the file here, so it can be
74 and exit with a proper error message when needed.
79 .Pa /var/run/ Ns Ao Va progname Ac Ns Pa .pid
83 function sets the O_CLOEXEC close-on-exec flag when opening the pidfile.
87 function writes process' PID into a previously opened file.
91 function closes a pidfile.
92 It should be used after daemon
94 to start a child process.
98 function closes and removes a pidfile.
102 function returns the file descriptor for the open pidfile.
106 function returns a valid pointer to a
108 structure on success, or
115 .Rv -std pidfile_write pidfile_close pidfile_remove
119 function returns the low-level file descriptor.
126 is specified, or if the pidfile is no longer open.
128 The following example shows in which order these functions should be used.
129 Note that it is safe to pass
140 pid_t otherpid, childpid;
142 pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid);
144 if (errno == EEXIST) {
145 errx(EXIT_FAILURE, "Daemon already running, pid: %jd.",
148 /* If we cannot create pidfile from other reasons, only warn. */
149 warn("Cannot open or create pidfile");
152 if (daemon(0, 0) == -1) {
153 warn("Cannot daemonize");
165 syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
172 syslog(LOG_INFO, "Child %jd started.", (intmax_t)childpid);
183 function will fail if:
186 Some process already holds the lock on the given pidfile, meaning that a
187 daemon is already running.
192 the function will use it to store a PID of an already running daemon or
194 in case daemon did not write its PID yet.
195 .It Bq Er ENAMETOOLONG
196 Specified pidfile's name is too long.
198 Some process already holds the lock on the given pidfile, but PID read
199 from there is invalid.
204 function may also fail and set
206 for any errors specified for the
215 function will fail if:
218 Improper function use.
219 Probably called before
225 function may also fail and set
227 for any errors specified for the
236 function may fail and set
238 for any errors specified for the
246 function will fail if:
249 Improper function use.
250 Probably called not from the process which made
256 function may also fail and set
258 for any errors specified for the
270 function will fail if:
273 Improper function use.
274 Probably called not from the process which used
285 functionality is based on ideas from
286 .An John-Mark Gurney Aq jmg@FreeBSD.org .
288 The code and manual page was written by
289 .An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .