First of all thanks for your fast reply.

Unfortunately the programs output I'm interested in is only available as a file. And this file doesn't have a fixed size.

lsof and subsequent grep would help over NFS, but I wanted to code portable. So I decided not to use this possibility.

I think your idea to check the file size regularly is very good although not 100% sure. I will try this.

Thanks again!

 to.b