Regular expressions: Ensuring b doesn't come between a and c

Question

Here\'s something I\'m trying to do with regular expressions, and I can\'t figure out how. I have a big file, and strings abc, 123 and xyz

Answer 1

Using PCRE a solution would be:

This using m flag. If you want to check only from start and end of a line add ^ and $ at beginning and end respectively

abc(?!.*(abc|xyz).*123).*123(?!.*(abc|xyz).*xyz).*xyz

Debuggex Demo