regex - How to exclude text between boundaries? -



regex - How to exclude text between boundaries? -

i'm trying understand why illustration regex not work way i'd to:

test-text: filename: test myfile 123 .txt pattern: (?<=filename:.*?myfile)(.*?)(?=.txt) expected result: 123

i know lookahead/behind not ideal here, it's learning purpose trying understand.

so why .*?myfile not work? if remove it, pattern matches test myfile 123. want filename:, exclude myfile, , take after , bewteen lastly .txt statement. missing here?

due complexities of regex matching, variable-length lookbehind pattern not supported. should error message effect. limitation of perl's regex engine.

there similar feature allows this: \k discards left final match. pattern work expect to:

/filename:.*?myfile\k(.*?)(?=.txt)/

it not same true lookbehind, however, in doesn't allow overlapping matches.

incidentally, 3rd similar question have posted. based on info have given, right reply still "don't utilize look-arounds this". if there reason want utilize them, should explain can give improve help.

regex

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