Monks

Thnx a lot for all the suggestions!!
Not only do I understand file locking a lot better (also thnx to bart although he confused the -w), but also I learned there is no really other way to prefent multi occurences of the same program without FileLocks.
The script I posted above does not only work on Linux, but it will also produce useful output on Unix (change 'aux' into '-ef').
Because I don't want to use lock-files, I think I will write my own LockFile.pm based on the above script (it will be very basic).

If there is a really good argument agains my approach I will abandon my precious and use FileLocks :)

LuCa