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33 .Nd "library for PID files handling"
39 .Fn pidfile_open "const char *path" "mode_t mode" "pid_t *pidptr"
41 .Fn pidfile_write "struct pidfh *pfh"
43 .Fn pidfile_close "struct pidfh *pfh"
45 .Fn pidfile_remove "struct pidfh *pfh"
47 .Fn pidfile_fileno "struct pidfh *pfh"
51 family of functions allows daemons to handle PID files.
54 to lock a pidfile and detect already running daemons.
58 function opens (or creates) a file specified by the
60 argument and locks it.
65 and file can not be locked, the function will use it to store a PID of an
66 already running daemon or
68 in case daemon did not write its PID yet.
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
81 function sets the O_CLOEXEC close-on-exec flag when opening the pidfile.
85 function writes process' PID into a previously opened file.
86 The file is truncated before write, so calling the
88 function multiple times is supported.
92 function closes a pidfile.
93 It should be used after daemon
95 to start a child process.
99 function closes and removes a pidfile.
103 function returns the file descriptor for the open pidfile.
107 function returns a valid pointer to a
109 structure on success, or
116 .Rv -std pidfile_write pidfile_close pidfile_remove
120 function returns the low-level file descriptor.
127 is specified, or if the pidfile is no longer open.
129 The following example shows in which order these functions should be used.
130 Note that it is safe to pass
141 pid_t otherpid, childpid;
143 pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid);
145 if (errno == EEXIST) {
146 errx(EXIT_FAILURE, "Daemon already running, pid: %jd.",
149 /* If we cannot create pidfile from other reasons, only warn. */
150 warn("Cannot open or create pidfile");
152 * Even though pfh is NULL we can continue, as the other pidfile_*
153 * function can handle such situation by doing nothing except setting
158 if (daemon(0, 0) == -1) {
159 warn("Cannot daemonize");
171 syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
178 syslog(LOG_INFO, "Child %jd started.", (intmax_t)childpid);
189 function will fail if:
192 Some process already holds the lock on the given pidfile, meaning that a
193 daemon is already running.
198 the function will use it to store a PID of an already running daemon or
200 in case daemon did not write its PID yet.
201 .It Bq Er ENAMETOOLONG
202 Specified pidfile's name is too long.
204 Some process already holds the lock on the given pidfile, but PID read
205 from there is invalid.
210 function may also fail and set
212 for any errors specified for the
221 function will fail if:
224 Improper function use.
225 Probably called before
231 function may also fail and set
233 for any errors specified for the
242 function may fail and set
244 for any errors specified for the
252 function will fail if:
255 Improper function use.
256 Probably called not from the process which made
262 function may also fail and set
264 for any errors specified for the
276 function will fail if:
279 Improper function use.
280 Probably called not from the process which used
300 functionality is based on ideas from
301 .An John-Mark Gurney Aq Mt jmg@FreeBSD.org .
303 The code and manual page was written by
304 .An Pawel Jakub Dawidek Aq Mt pjd@FreeBSD.org .