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I need to extract with -o1 a group that is matched in lines that do not contain a string.

If I use -v pcregrep does not match any groups - which is reasonable: I'm asking to group-match something in patterns that I'm excluding.

How can I deal with that?

Thanks in advance for any help.

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Assuming I've understood your need correctly, if your match command takes the form pcregrep -o1 '(match)', the corresponding regex that would report a match only if another string is not matched is pcregrep -o1 '^(?!.*donotmatch).*(match)'. Look up negative lookahead expressions in the PCRE documentation. Also notice the .* in front of the (match); this is needed due the anchoring of the negative looking ahead expression to the start of the line via the ^

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  • Thanks @iruvar, would it be the same regex as (?<!.*donotmatch).*(match).*(?!.*donotmatch) ? Commented Jun 22, 2019 at 23:19
  • @AntonMariaPrati, non-fixed length lookbehind assertions don't work. (?<!.*donotmatch) is not valid regex Commented Jun 22, 2019 at 23:25

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