I would probably do find -name '*.txt' -exec bash -c 'mv -nv "$0" "${0/.txt/.bak}"' {} \; That's not at all user-friendly, but these are supposed to be pro

I would probably do find -name '*.txt' -exec bash -c 'mv -nv "$0" "${0/.txt/.bak}"' {} \; That's not at all user-friendly, but these are supposed to be programmer tools... If you want user-friendly file operations on UNIX command line, use midnight commander. It can do mass rename, etc.