my $greatest = 0;
open(CONFIG, "<$config_file") or die $!;
while (my $line = <CONFIG>) {
  my ($login, $pass, $UID, $gid, $name, $home_dir, $shell) = split(':',$line);
  if($UID > $greatest && $UID != 65534){
    $greatest = $UID;
  }
}
close CONFIG;
print "groesste UID: ",$greatest,"\n"