Thanks again, Kenosis. Yes, indeed. Entering the third option without brackets, does create a text file, but without any results(?) The files, I am looking for, however do exist in the directory. So they should be found.
Hmm.. If I get the two arrays (@ds and @dirFile) in my script listed, I can see that grep /$line/ should find the matching elements in the second array. But @results keeps beeing empty. The funny thing is: if I define @ds writing some of the wanted IDs directly into the script @ds = ("I C 7702", "I C 7710");
the script works perfectly. But I want the array filled by reading a long list of IDs from a text file. Any idea what is going wrong?