Every now and then I want to rename files in a folder according to a pattern. Mostly it is to hook up audio books in my iPod. Then I have to rename all the files with .m4a extension to .m4b (and don’t ask me why apple did choose this idiotic solution).
This is easily done with a dos command in windows (ren *.m4a *.m4b). But when you want to change file names according to a pattern it gets trickier. I stumbled across this sometimes when I want to rename digital photos and such.