Question

I’m trying to do link rewriting in my mobile application (written in ruby). I would like it to be able to accomplish both of these rewrites with a single regular expression:

m.example.com -> www.example.com
m.subd.example.com -> subd.example.com

The closest I’ve gotten replacing this:

m\.([a-z\.]*)example\.com

with this:

$1example.com

This works for the m.subd.example.com but it fails for m.example.com because of my “www.” exception.

I do this A LOT so i’d like it to be very fast, which is why I am trying to avoid using any code, just a single regex. Is it possible? Is there a fancy feature of regex that I don’t know about?

Answer 1

I am trying to avoid using any code, just a single regex

Regex is code. A more complex regex takes longer to run. You’ll need to write some code or run two regexes.

result = subject.gsub(/m\.([a-z.]*)example\.com/, '\1example.com').gsub(/^example\.com/, 'www.example.com')