I have two problems, one of them is a regex

Question

I am updating some code that I didn't write and part of it is a regex as follows:

\[url(?:\s*)\]www\.(.*?)\[/url(?:\s*)\]

I understand that .*? does a non-greedy match of everything in the second register.

What does ?:\s* in the first and third registers do?

Update: As requested, language is C# on .NET 3.5

Answer 1

The syntax (?:) is a way of putting parentheses around a subexpression without separately extracting that part of the string.

The author wanted to match the (.*?) part in the middle, and didn't want the spaces at the beginning or the end from getting in the way. Now you can use \1 or $1 (or whatever the appropriate method is in your particular language) to refer to the domain name, instead of the first chunk of spaces at the beginning of the string