Regex: optional group

Question

I want to split a string like this:

abc//def//ghi

into a part before and after the first occurrence of //:

a: abc
b: //def//ghi

I'm currently using this regex:

(?<a>.*?)(?<b>//.*)

Which works fine so far.

However, sometimes the // is missing in the source string and obviously the regex fails to match. How is it possible to make the second group optional?

An input like abc should be matched to:

a: abc
b: (empty)

I tried (?<a>.*?)(?<b>//.*)? but that left me with lots of NULL results in Expresso so I guess it's the wrong idea.

Answer 1

Try a ^ at the begining of your expression to match the begining of the string and a $ at the end to match the end of the string (this will make the ungreedy match work).

^(?<a>.*?)(?<b>//.*)?$