Question

I have the following sample expression that I’m passing to egrep over a word list:

^([a-z])lu([a-z])\2er$

I’d like to further stipulate that the content of \1 and \2 must be different, e.g. this would match “bluffer” but not “blubber”. Is there a way to build this into the expression itself (so I can get my results right from egrep or something like it), or am I stuck doing this in some real language with regular expression support and manually checking that none of my groups are the same?

Answer 1

You need something more powerful. Regular expressions can’t track state. Sed could probably do what you need.