Turns files name *.001, *.002, *.003 into *.r01, *.r02, *.r03
require 'fileutils' Dir.entries(File.dirname(__FILE__)).each { FileUtils.mv(File.join(File.dirname(__FILE__), entry), File.join(File.dirname(__FILE__), entry.gsub!(/\.(0)(\d+)\z/, '.r\2')), :verbose => true) if entry[/\.(0)(\d+)\z/]}