text: /*
   * This code is mainly taken from Doug Potter's page
   *
   * http://www-theorie.physik.unizh.ch/~dpotter/howto/daemonize
   *
   * I contacted him 2007-04-16 about the license for the original code,
   * he replied it is Public Domain.  Use the URL above to get the original
   * Public Domain version if you want it.
   *
   * This version is LGPL2.1+SLE like the rest of libwebsockets and is
   * Copyright (c)2006 - 2013 Andy Green <andy@warmcat.com>
   *
   *
   * You're much better advised to use systemd to daemonize stuff without needing
   * this kind of support in the app itself.
   */
  
  #include <stdlib.h>
  #include <string.h>
  #include <stdio.h>
  #include <signal.h>
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <fcntl.h>
  #include <limits.h>
  #include <unistd.h>
  #include <errno.h>
  
  #include "private-lib-core.h"
  
  pid_t pid_daemon;
  static char *lock_path;
  
  pid_t get_daemonize_pid()
  {
  	return pid_daemon;
  }
  
  static void
  child_handler(int signum)
  {
  	int len, sent, fd;
  	char sz[20];
  
  	switch (signum) {
  
  	case SIGALRM: /* timed out daemonizing */
  		exit(0);
  		break;
  
  	case SIGUSR1: /* positive confirmation we daemonized well */
  
  		if (!lock_path)
  			exit(0);
  
  		/* Create the lock file as the current user */
  
  		fd = lws_open(lock_path, O_TRUNC | O_RDWR | O_CREAT, 0640);
  		if (fd < 0) {
  			fprintf(stderr,
  			   "unable to create lock file %s, code=%d (%s)\n",
  				lock_path, errno, strerror(errno));
  			exit(0);
  		}
  		len = sprintf(sz, "%u", (unsigned int)pid_daemon);
  		sent = write(fd, sz, len);
  		if (sent != len)
  			fprintf(stderr,
  			  "unable to write pid to lock file %s, code=%d (%s)\n",
  					     lock_path, errno, strerror(errno));
  
  		close(fd);
  
  		exit(0);
  		//!!(sent == len));
  
  	case SIGCHLD: /* daemonization failed */
  		exit(0);
  		break;
  	}
  }
  
  static void lws_daemon_closing(int sigact)
  {
  	if (getpid() == pid_daemon)
  		if (lock_path) {
  			unlink(lock_path);
  			lws_free_set_NULL(lock_path);
  		}
  
  	kill(getpid(), SIGKILL);
  }
  
  /*
   * You just need to call this from your main(), when it
   * returns you are all set "in the background" decoupled
   * from the console you were started from.
   *
   * The process context you called from has been terminated then.
   */
  
  LWS_VISIBLE int
  lws_daemonize(const char *_lock_path)
  {
  	struct sigaction act;
  	pid_t sid, parent;
  
  	/* already a daemon */
  //	if (getppid() == 1)
  //		return 1;
  
  	if (_lock_path) {
  		int n;
  
  		int fd = lws_open(_lock_path, O_RDONLY);
  		if (fd >= 0) {
  			char buf[10];
  
  			n = read(fd, buf, sizeof(buf));
  			close(fd);
  			if (n) {
  				int ret;
  				n = atoi(buf);
  				ret = kill(n, 0);
  				if (ret >= 0) {
  					fprintf(stderr,
  					     "Daemon already running pid %d\n",
  					     n);
  					exit(1);
  				}
  				fprintf(stderr,
  				    "Removing stale lock %s from dead pid %d\n",
  							_lock_path, n);
  				unlink(lock_path);
  			}
  		}
  
  		n = strlen(_lock_path) + 1;
  		lock_path = lws_malloc(n, "daemonize lock");
  		if (!lock_path) {
  			fprintf(stderr, "Out of mem in lws_daemonize\n");
  			return 1;
  		}
  		strcpy(lock_path, _lock_path);
  	}
  
  	/* Trap signals that we expect to receive */
  	signal(SIGCHLD, child_handler);	/* died */
  	signal(SIGUSR1, child_handler); /* was happy */
  	signal(SIGALRM, child_handler); /* timeout daemonizing */
  
  	/* Fork off the parent process */
  	pid_daemon = fork();
  	if ((int)pid_daemon < 0) {
  		fprintf(stderr, "unable to fork daemon, code=%d (%s)",
  		    errno, strerror(errno));
  		exit(9);
  	}
  
          /* If we got a good PID, then we can exit the parent process. */
  	if (pid_daemon > 0) {
  
                 /*
                  * Wait for confirmation signal from the child via
                  * SIGCHILD / USR1, or for two seconds to elapse
                  * (SIGALRM).  pause() should not return.
                  */
                 alarm(2);
  
                 pause();
                 /* should not be reachable */
                 exit(1);
         }
  
  	/* At this point we are executing as the child process */
  	parent = getppid();
  	pid_daemon = getpid();
  
  	/* Cancel certain signals */
  	signal(SIGCHLD, SIG_DFL); /* A child process dies */
  	signal(SIGTSTP, SIG_IGN); /* Various TTY signals */
  	signal(SIGTTOU, SIG_IGN);
  	signal(SIGTTIN, SIG_IGN);
  	signal(SIGHUP, SIG_IGN); /* Ignore hangup signal */
  
  	/* Change the file mode mask */
  	umask(0);
  
  	/* Create a new SID for the child process */
  	sid = setsid();
  	if (sid < 0) {
  		fprintf(stderr,
  			"unable to create a new session, code %d (%s)",
  			errno, strerror(errno));
  		exit(2);
  	}
  
  	/*
  	 * Change the current working directory.  This prevents the current
  	 * directory from being locked; hence not being able to remove it.
  	 */
  	if (chdir("/tmp") < 0) {
  		fprintf(stderr,
  			"unable to change directory to %s, code %d (%s)",
  			"/", errno, strerror(errno));
  		exit(3);
  	}
  
  	/* Redirect standard files to /dev/null */
  	if (!freopen("/dev/null", "r", stdin))
  		fprintf(stderr, "unable to freopen() stdin, code %d (%s)",
  						       errno, strerror(errno));
  
  	if (!freopen("/dev/null", "w", stdout))
  		fprintf(stderr, "unable to freopen() stdout, code %d (%s)",
  						       errno, strerror(errno));
  
  	if (!freopen("/dev/null", "w", stderr))
  		fprintf(stderr, "unable to freopen() stderr, code %d (%s)",
  						       errno, strerror(errno));
  
  	/* Tell the parent process that we are A-okay */
  	kill(parent, SIGUSR1);
  
  	act.sa_handler = lws_daemon_closing;
  	sigemptyset(&act.sa_mask);
  	act.sa_flags = 0;
  
  	sigaction(SIGTERM, &act, NULL);
  
  	/* return to continue what is now "the daemon" */
  
  	return 0;
  }
  
  