Match text between characters (avoid nesting)

Question

Given:

"abc{defghij{kl}mnopqrst}uvwxyz{aaaaaaaaaa}"

I want to match the text between the characters { and the last } excluding nesting - i.e. the texts {defghij{kl}mnopqrst} and {aaaaaaaaaa}.

Without the nested {kl}, the regex expression \{[^{}]*\} works just fine. But not with the nested {kl}.

Is there a way to do this? If not possible, can I say "match text between { and } where the size of the enclosed text is at least, e.g. 3, characters so that the nested {kl} which contains two characters is not matched? (I'm assuming one level nesting)

Editor: https://www.freeformatter.com/java-regex-tester.html

Thanks,

See https://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags?rq=1 — bmargulies, Dec 08 '18 at 05:05
Java doesn't support the sort of recursing you'd like, unfortunately (in PCRE you could `{(?:(?R)|[^{}])+}`) — CertainPerformance, Dec 08 '18 at 05:27
If you are sure that nested levels wouldn't go more than one then you can safely use this `{(?:{[^{}]*}|[^{}]+)*}`. See live demo here https://regex101.com/r/N13a2K/1 — revo, Dec 08 '18 at 05:37
It works ([see it here](https://ideone.com/dF0mQO)). It just needs a few proper escaping in Java. — revo, Dec 08 '18 at 05:48
Thanks! Please post it as an answer so that I close it as answered. — cmutex, Dec 08 '18 at 05:53
My pleasure but are you sure that nested levels will not go more than that? — revo, Dec 08 '18 at 05:55

score 1 · Accepted Answer · answered Dec 08 '18 at 06:30

In your problem since nesting levels will not reach two, it is possible to solve it with a readable, short regex and that would be:

\{(?:\{[^{}]*}|[^{}]+)*}

In Java you have to escape opening braces, as I did.

Above regex matches an opening brace then looks for either something other than { and } characters (i.e. [^{}]+) or something enclosed in braces {[^{}]*} and repeats this pattern as much as possible then expects to match a closing brace.

See live demo here

Match text between characters (avoid nesting)

1 Answers1