sub create_link($) {
  my $filehandle = shift(@_);
  my $max_wartezeit = 3;
  my $fehler = '';
  sysopen ($filehandle, "sysopentest.txt", O_RDWR | O_CREAT, 0600) or $fehler = $!;
  if (!$fehler) {
    my $start = time;
    while(!flock($filehandle,LOCK_EX|LOCK_NB) && time-$start<$max_wartezeit){
      sleep 1;
    }
  $fehler = 'Timeout on flock' if !flock ($filehandle, LOCK_EX | LOCK_NB);
  }
  return $fehler;
}