regex, extract string NOT between two brackets

Question

OK regex question , how to extract a character NOT between two characters, in this case brackets.

I have a string such as: word1 | {word2 | word3 } | word 4

Answer 1

Depends on the language/implementation you're using, but...

\|(?![^{]*})

This matches a pipe that is not followed by a } except in the case that a { comes first.

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The (?! ... ) is known as a negative lookahead assertion. This is easier to understand if we start with a positive lookahead assertion:

\|(?=[^{]*})

The above only matches a pipe that is followed by a } without encountering a { first. When you negate that by replacing the = with a !, the match is now only successful if there's no way for the positive case to be true (also known as the complement).