Question

Is it possible to use a regex to create a pattern that matches fragments that do NOT contain a certain string?

This magic regex would take this input and examine whats between the parenthesis:
(foo bar) (barfoo) (zab) (foozab) and only return zab because it doesn’t contain foo between the parenthesis.

Is this possible, or should I just capture everything between parenthesis and use a langauge function to exclude them?

Answer 1

Depending on the engine, you can use a lookahead assertion.

\(((?:(?!foo)[^)])+)\)

That regex will match a parenthesized string where the characters inside the string do not ever match the sub-expression “foo” (which in this case is just a string).

Here it is in expanded form:

\(          # match the opening (
  (         # capture the text inside the parens
   (?:      # we need another group, but don't capture it
    (?!foo) # fail if the sub-expression "foo" matches at this point
    [^)]    # match a non-paren character
   )+       # repeat that group
  )         # end the capture
\)          # end the parens