How to tame a mess of unnamed (and unextension named) files from Usenet, on a Synology NAS. Requires SABnzbd installed.

make-par.bash

# For every file in a given directory
for x in *
do
  if [ "`file $x |cut -d' ' -f 2-`" == "Parity Archive Volume Set" ] # If the file is determined to be a PAR file
  then
    # Print the filename and file type again as a confirmation
    file $x
    mv $x ${x}.par2 # Rename it to have a .par2 extension
  fi
done

# For every now par2 file; scan every file that it might apply to, and (-p) delete PAR files after successful or non-necessary recovery
for x in *.par2 ; do /volume1/\@appstore/sabnzbd/bin/par2repair -p $x * ; done