sub Daemonize {
  return if ($^O eq 'MSWin32');
  chdir '/'                 or die "Can't chdir to /: $!";
  umask 0;
  open STDIN, '/dev/null'   or die "Can't read /dev/null: $!";
  open STDOUT, '>/dev/null' or die "Can't write to '>/dev/null': $!";
  open STDERR, '>/dev/null' or die "Can't write to /dev/null: $!";
  defined(my $pid = fork)   or die "Can't fork: $!";
  exit if $pid;
  setsid                    or die "Can't start a new session: $!";
  if (-e '/www/run/update_selena.pid') {
    die "Process is running"
  }
  open PID, '>/www/run/update_selena.pid' or die "Can't write pid: $!";
  print PID $$;
  close PID;
}