Kedves Szabolcs,
First of all, with the CERN version of FLUKA you can call the post processing programs directly, as their folder is included in your $PATH. ($FLUPRO/flutil/ is the obsolete location of these programs)
Unfortunately you can’t pass arguments to these scripts, but it is possible to create a text file (input_file) containing the fort files you want to process and the name of the desired output file (without the extension). For example:
run001_fort.21
run002_fort.21
run003_fort.21
output_filename
Then you can feed this file to the post processing programs via the standard Linux pipes:
usbsuw < input_file
I hope this helps.
Üdv.:
Dávid