Question

I have some text that consists of space separated arbitrary-length codes, example:

AA *X IJ XYZ 7F *A OF *B 3C

As a first step, I want to extract all of the codes that are 2 characters where the first character is an asterisk, and the second character is one of 3 different alternatives (let’s say they’re A, B & C). So after this step, in this example I would have as my list of matches *A and *B.

I tried using the following regex

\b(\*[ABC])\b

…but of course, that doesn’t work because the asterisk isn’t considered part of a word. How can I do this in a readable, maintainable manner?

Answer 1

Use a positive lookbehind, and match either the begining of the string or a space character:

(<=^| )(\*[ABC])\b

See it here in action: http://regex101.com/r/wS5qS2

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If all you care about is the capture group, you don’t need the lookbehind. Just keep it out of your capture group:

(?:^| )(\*[ABC])\b