It's a much more generic way of saying it, e.g. you can't use the other way for ls | grep -P "roc_(nightly|weekly).*\.tar\.gz" | xargs rm (forgive me if I

It's a much more generic way of saying it, e.g. you can't use the other way for ls | grep -P "roc_(nightly|weekly).*\.tar\.gz" | xargs rm (forgive me if I got grep -P regex syntax wrong)