If you can't write a shell script without being sure your variables are set, then don't write it in shell. A MANIFEST is not the right answer. Steam deals with

If you can't write a shell script without being sure your variables are set, then don't write it in shell. A MANIFEST is not the right answer. Steam deals with any number of third-party games which may drop any number of files into these directories. The best way to nuke a directory is 'rm -rf "$DIRECTORY"'. Any amount of "well what if $DIRECTORY points to the wrong place" has nothing to do with the removal operation itself.