Simple, unoptimized example for Linux (which doesn't even require to change the drmcheck.py file):
Code:
find . -type f -print0 | sort -z | xargs -0 -n1 -i sh -c 'echo -n "{}: "; python ~/kindle-touch/drm/drmcheck.py "{}"' | egrep -v '^$' | grep -v "Unknown ebook" > /tmp/list.txt
I don't know how this can be done with the Windows "shell" though.