How to negate specific word in regex? [duplicate]

A great way to do this is to use negative lookahead:

^(?!.*bar).*$

The negative lookahead construct is the pair of parentheses, with the opening parenthesis followed by a question mark and an exclamation point. Inside the lookahead [is any regex pattern].

Unless performance is of utmost concern, it's often easier just to run your results through a second pass, skipping those that match the words you want to negate.

Regular expressions usually mean you're doing scripting or some sort of low-performance task anyway, so find a solution that is easy to read, easy to understand and easy to maintain.

You could either use a negative look-ahead or look-behind:

^(?!.*?bar).*
^(.(?<!bar))*?$

Or use just basics:

^(?:[^b]+|b(?:$|[^a]|a(?:$|[^r])))*$

These all match anything that does not contain bar.

Solution:

^(?!.*STRING1|.*STRING2|.*STRING3).*$

xxxxxx OK

xxxSTRING1xxx KO (is whether it is desired)

xxxSTRING2xxx KO (is whether it is desired)

xxxSTRING3xxx KO (is whether it is desired)

The following regex will do what you want (as long as negative lookbehinds and lookaheads are supported), matching things properly; the only problem is that it matches individual characters (i.e. each match is a single character rather than all characters between two consecutive "bar"s), possibly resulting in a potential for high overhead if you're working with very long strings.

b(?!ar)|(?<!b)a|a(?!r)|(?<!ba)r|[^bar]