Imagine I have a string like this:
c x c x A c x c x c B c x c x
And I want to find any "c" character that is between "A" and "B". So in this example I need to get 3 matches.
I know that I can use lookahead and lookbehind tokens. So I used this regex:
(?<=A).*c.*(?=B)
But it gets all the sting between A and B: c x c x c as one result.
And if I remove the .* parts, there will be no match at all.
I made an example here. so you can see the results.
There are two common scenarios here: 1) the A and B are different single character strings, 2) A and B are different mutlicharacter strings.
Scenario 1
You may use negated character classes:
(?:\G(?!^)|A)[^AB]*?\Kc(?=[^AB]*B)
See this regex demo. Details:
(?:\G(?!^)|A) - A or end of the previous successful match[^AB]*? - any zero or more chars other than A and B, as few as possible\K - match reset operator that discards all text matched so far in the overall memory match bufferc - a c char/string(?=[^AB]*B) - that must be followed with zero or more chars other than A and B and then B char immediately to the right of the current location.Scenario 2
If A and B are placeholders for multichar strings, say, ABC and BCE and the c is some pattern like c\d+ (to match c and one or more digits after it) use
(?s)(?:\G(?!^)|ABC)(?:(?!ABC).)*?\Kc\d+(?=.*?BCE)
See this regex demo. Details:
(?s) - a DOTALL modifier that makes the regex engine match any char with .(?:\G(?!^)|ABC) - ABC or end of the previous successful match(?:(?!ABC).)*? - any char, 0 or more times, that does not start an ABC char sequence\K - match reset operatorc\d+ - c and one or more digits(?=.*?BCE) - any zero or more chars, as few as possible, followed with BCE.