建立守護進程的簡單樣本

int daemonise ()
{
  int nullfd;
  pid_t pid;
  if ((nullfd = open ("/dev/null", O_WRONLY, 0)) == -1)
    {
      return -1;
    }
  if ((pid = fork ()) < 0)
    {
      return -1;
    }
  else if (pid != 0)
    {
      close (nullfd);
      exit (0);                 // parent goes bye-bye
    }
  // child continues
  dup2 (nullfd, STDIN_FILENO);  // stdin
  dup2 (nullfd, STDOUT_FILENO); // stdout
  dup2 (nullfd, STDERR_FILENO); // stderr
  close (nullfd);

  setsid ();                    // become session leader
  chdir ("/");                  // change working directory
  umask (0);                    // clear our file mode creation mask
  return 0;
}