Question

I am trying to construct a regex to extract a domain given a url.

for:

http://www.abc.google.com/
http://abc.google.com/
https://www.abc.google.com/
http://abc.google.com/

should give:

abc.google.com

Answer 1

URI.parse('http://www.abc.google.com/').host
#=> "www.abc.google.com"

Not a regex, but probably more robust then anything we come up with here.

URI.parse('http://www.abc.google.com/').host.gsub(/^www\./, '')

If you want to remove the www. as well this will work without raising any errors if the www. is not there.