Yup, -i is very very useful, though I prefer to always call it as -i.bak (=> do the edit in place and make a backup of the original file as "filename.original.b

Yup, -i is very very useful, though I prefer to always call it as -i.bak (=> do the edit in place and make a backup of the original file as "filename.original.bak"), in case I do something hideously wrong. For what it's worth (you may know this but maybe not everyone does), Ruby also provides the -i flag.