how to find a regex pattern inside a regex pattern

Question

I have some text like the following:

between [... between (...)] and (...) as ...

with the regex

between\s+(.+?)\s+and\s+(.+?)\s+as

I am trying to capture what are inside two pairs of parentheses, i.e., the contents bounded by between and and. However I am stuck in that it always returns content in the square brackets and the second pair of parentheses.

EDIT:

for example if the text is:

between foo whatever between bar and dummy as

I want the regex to extract 'bar' and 'dummy', not 'foo whatever between bar' and 'dummy'

Regular expressions can't easily deal with nested structures, you need a recursive descent parser. — Barmar
– Barmar, Commented Apr 10, 2018 at 21:13
@Barmar is it possible to use negative look ahead ? I cannot make it work though. — Sheng
– Sheng, Commented Apr 10, 2018 at 21:27
No, negative lookahead won't help. I assume you allow arbitrary levels of nesting. — Barmar
– Barmar, Commented Apr 10, 2018 at 21:28

revo · Accepted Answer · 2018-04-10 21:47:04Z

3

Prepend your regex with .* or use a negative lookahead:

between(?!.*between\b)\s+(.+?)\s+and\s+(.+?)\s+as

Live demo

edited Apr 10, 2018 at 21:47

answered Apr 10, 2018 at 21:28

revo

49k15 gold badges84 silver badges123 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

asdf Over a year ago

This doesn't match the word dummy

revo Over a year ago

Please check live demo. It does. @asdf

Aran-Fey Over a year ago

Eh, I'm not a fan of that lookahead. If the word "between" appears anywhere later in the string, your regex won't match anything. Like in between x and y as between -> no match. You should rewrite that to (?:(?!between\b).)*.

asdf Over a year ago

@revo, yes it does if the word as is prepended which it was not in the post, but it appears that is the context

Aran-Fey Over a year ago

Is it? I think it's about making the text matched by the first group as short as possible. If that's what the question is about, why would you suggest prepending .*? That does something completely different than your lookahead.

|

asdf · Accepted Answer · 2018-04-10 21:28:21Z

0

In the case of your specific problem, you need to match the whitespace leading up to the between in question (which seems to be the limiting factor). I was able to achieve the results with the following:

^.+(\s)between\s(.+?)\sand\s(.+?)$

answered Apr 10, 2018 at 21:28

asdf

3,0872 gold badges24 silver badges43 bronze badges

Comments

Mohammed Elhag · Accepted Answer · 2018-04-10 21:51:27Z

0

Try this :

between\s([^\s]+)\sand\s([^\s]+)

https://regex101.com/r/Vjkr0h/5

answered Apr 10, 2018 at 21:51

Mohammed Elhag

4,3201 gold badge12 silver badges19 bronze badges

Collectives™ on Stack Overflow

how to find a regex pattern inside a regex pattern

3 Answers 3

8 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

8 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related