Question

I have a bunch of domain names coming in like this:

http://subdomain.example.com (example.com is always example.com, but the subdomain varies).

I need “subdomain”.

Could some kind person who had the patience to learn regex help me out?

Answer 1

/(http:\/\/)?(([^.]+)\.)?domain\.com/

Then $3 (or \3) will contain “subdomain” if one was supplied.

If you want to have the subdomain in the first group, and your
regex engine supports non-capturing groups (shy groups), use
this as suggested by palindrom:

/(?:http:\/\/)?(?:([^.]+)\.)?domain\.com/