2 * This code is mainly taken from Doug Potter's page
4 * http://www-theorie.physik.unizh.ch/~dpotter/howto/daemonize
6 * I contacted him 2007-04-16 about the license for the original code,
7 * he replied it is Public Domain. Use the URL above to get the original
8 * Public Domain version if you want it.
10 * This version is LGPL2.1+SLE like the rest of libwebsockets and is
11 * Copyright (c)2006 - 2013 Andy Green <andy@warmcat.com>
18 #include <sys/types.h>
25 #include "private-libwebsockets.h"
28 static char *lock_path;
30 int get_daemonize_pid()
36 child_handler(int signum)
43 case SIGALRM: /* timed out daemonizing */
47 case SIGUSR1: /* positive confirmation we daemonized well */
50 /* Create the lock file as the current user */
52 fd = open(lock_path, O_TRUNC | O_RDWR | O_CREAT, 0640);
55 "unable to create lock file %s, code=%d (%s)\n",
56 lock_path, errno, strerror(errno));
59 len = sprintf(sz, "%u", pid_daemon);
60 sent = write(fd, sz, len);
63 "unable to write pid to lock file %s, code=%d (%s)\n",
64 lock_path, errno, strerror(errno));
71 case SIGCHLD: /* daemonization failed */
77 static void lws_daemon_closing(int sigact)
79 if (getpid() == pid_daemon)
82 lws_free_set_NULL(lock_path);
85 kill(getpid(), SIGKILL);
89 * You just need to call this from your main(), when it
90 * returns you are all set "in the background" decoupled
91 * from the console you were started from.
93 * The process context you called from has been terminated then.
97 lws_daemonize(const char *_lock_path)
104 /* already a daemon */
105 // if (getppid() == 1)
109 fd = open(_lock_path, O_RDONLY);
111 n = read(fd, buf, sizeof(buf));
118 "Daemon already running from pid %d\n", n);
122 "Removing stale lock file %s from dead pid %d\n",
128 n = strlen(_lock_path) + 1;
129 lock_path = lws_malloc(n);
131 fprintf(stderr, "Out of mem in lws_daemonize\n");
134 strcpy(lock_path, _lock_path);
137 /* Trap signals that we expect to receive */
138 signal(SIGCHLD, child_handler); /* died */
139 signal(SIGUSR1, child_handler); /* was happy */
140 signal(SIGALRM, child_handler); /* timeout daemonizing */
142 /* Fork off the parent process */
144 if (pid_daemon < 0) {
145 fprintf(stderr, "unable to fork daemon, code=%d (%s)",
146 errno, strerror(errno));
150 /* If we got a good PID, then we can exit the parent process. */
151 if (pid_daemon > 0) {
154 * Wait for confirmation signal from the child via
155 * SIGCHILD / USR1, or for two seconds to elapse
156 * (SIGALRM). pause() should not return.
161 /* should not be reachable */
165 /* At this point we are executing as the child process */
167 pid_daemon = getpid();
169 /* Cancel certain signals */
170 signal(SIGCHLD, SIG_DFL); /* A child process dies */
171 signal(SIGTSTP, SIG_IGN); /* Various TTY signals */
172 signal(SIGTTOU, SIG_IGN);
173 signal(SIGTTIN, SIG_IGN);
174 signal(SIGHUP, SIG_IGN); /* Ignore hangup signal */
176 /* Change the file mode mask */
179 /* Create a new SID for the child process */
183 "unable to create a new session, code %d (%s)",
184 errno, strerror(errno));
189 * Change the current working directory. This prevents the current
190 * directory from being locked; hence not being able to remove it.
192 if (chdir("/tmp") < 0) {
194 "unable to change directory to %s, code %d (%s)",
195 "/", errno, strerror(errno));
199 /* Redirect standard files to /dev/null */
200 if (!freopen("/dev/null", "r", stdin))
201 fprintf(stderr, "unable to freopen() stdin, code %d (%s)",
202 errno, strerror(errno));
204 if (!freopen("/dev/null", "w", stdout))
205 fprintf(stderr, "unable to freopen() stdout, code %d (%s)",
206 errno, strerror(errno));
208 if (!freopen("/dev/null", "w", stderr))
209 fprintf(stderr, "unable to freopen() stderr, code %d (%s)",
210 errno, strerror(errno));
212 /* Tell the parent process that we are A-okay */
213 kill(parent, SIGUSR1);
215 act.sa_handler = lws_daemon_closing;
216 sigemptyset(&act.sa_mask);
219 sigaction(SIGTERM, &act, NULL);
221 /* return to continue what is now "the daemon" */