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

The comment by hvd is quite appropriate, and this just provides an example. In SQL, for instance, I think it would be clearer to do:

where val like 'abc%123%xyz' and
      val not like 'abc%abc%' and
      val not like '%xyz%xyz'

I imagine something quite similar is simple to do in other environments.