Question

I have a string I read from a configuration file. Structure of the string is as follows;

(long_string)long_string(long_string)

Any item in brackets, including the brackets themselves, are optional. I have the following regular expression matching the whole string but I could not figure out how to make some parts of the regular expression optional with “?”.

Here are a few valid strings for input

(a)like(1)
like(very long string here)
like

Here is my regexp only matching the first one;

^\((?<short>.*)\)(?<text>.*)\((?<return>.*)\)$

How can I convert my regexp to make brackets optional for a match?

Answer 1

Surround the two sub-patterns with non-matching groups (?:expr) and make them optional:

^(?:\((?<short>.*)\))?(?<text>.*)(?:\((?<return>.*)\))?$

And if possible make the universal expression .* more specific, maybe with [^()]+:

^(?:\((?<short>[^()]+)\))?(?<text>[^()]+)(?:\((?<return>[^()]+)\))?$