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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 library provides functions for daemons to handle file with PID.
55 to lock pidfile and detect already running daemons.
59 function opens (or creates) a file specified by
61 argument and locks it with
64 If file can not be locked, PID of already running daemon is returned in
66 argument (if it is not NULL).
67 The function doesn't write process' PID into the file here, so it can be
68 used before fork()ing and exit with proper error message when needed.
72 .Pa /var/run/<progname>.pid
77 function write process' PID into previously opened file.
81 function closes pidfile.
82 It should be used after daemon fork()s to start a child process.
86 function closes and removes pidfile.
90 function return a valid pointer to a pidfh structure on success or
93 If an error does occur,
96 .Rv -std pidfile_write pidfile_close pidfile_remove
98 The following example shows in which order those functions should be used.
101 pid_t otherpid, childpid;
103 pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid);
106 errx(EXIT_FAILURE, "Daemon already running, pid: %d.", otherpid);
107 /* If we cannot create pidfile from other reasons, only warn. */
108 warn("Cannot open or create pidfile");
111 if (daemon(0, 0) == -1) {
112 warn("Cannot daemonize");
124 syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
131 syslog(LOG_INFO, "Child %d started.", childpid);
142 function will fail if:
145 Some process already holds the lock on the given pidfile, which means,
146 daemon is already running.
147 .It Bq Er ENAMETOOLONG
148 Specified pidfile's name is too long.
150 Some process already holds the lock on the given pidfile, but PID read
151 from there is invalid.
156 function may also fail and set
158 for any errors specified for the
166 function will fail if:
169 Inproper function use.
170 Probably called before
176 function may also fail and set
178 for any errors specified for the
186 function may fail and set
188 for any errors specified for the
195 function will fail if:
198 Inproper function use.
199 Probably called not from the process which made
205 function may also fail and set
207 for any errors specified for the
223 functionality is based on ideas from
224 .An John-Mark Gurney Aq jmg@FreeBSD.org .
226 The code and manual page was written by
227 .An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .