regex - Regular expression to match balanced parentheses

Question

I need a regular expression to select all the text between two outer brackets.

Example: some text(text here(possible text)text(possible text(more text)))end text

Result: (text here(possible text)text(possible text(more text)))

Answer 1

I want to add this answer for quickreference. Feel free to update.

---

.NET Regex using balancing groups.

((?>((?<c>)|[^()]+|)(?<-c>))*(?(c)(?!)))

Where c is used as the depth counter.

Demo at Regexstorm.com

• Stack Overflow: Using RegEx to balance match parenthesis
• Wes' Puzzling Blog: Matching Balanced Constructs with .NET Regular Expressions
• Greg Reinacker's Weblog: Nested Constructs in Regular Expressions

---

PCRE using a recursive pattern.

((?:[^)(]+|(?R))*+)

Demo at regex101; Or without alternation:

((?:[^)(]*(?R)?)*+)

Demo at regex101; Or unrolled for performance:

([^)(]*+(?:(?R)[^)(]*)*+)

Demo at regex101; The pattern is pasted at (?R) which represents (?0).

Perl, PHP, Notepad++, R: perl=TRUE, Python: Regex package with (?V1) for Perl behaviour.

---

Ruby using subexpression calls.

With Ruby 2.0 g<0> can be used to call full pattern.

((?>[^)(]+|g<0>)*)

Demo at Rubular; Ruby 1.9 only supports capturing group recursion:

(((?>[^)(]+|g<1>)*))

Demo at Rubular  (atomic grouping since Ruby 1.9.3)

---

JavaScript  API :: XRegExp.matchRecursive

XRegExp.matchRecursive(str, '\(', '\)', 'g');

JS, Java and other regex flavors without recursion up to 2 levels of nesting:

((?:[^)(]+|((?:[^)(]+|([^)(]*))*))*)

Demo at regex101. Deeper nesting needs to be added to pattern.
To fail faster on unbalanced parenthesis drop the + quantifier.

---

Java: An interesting idea using forward references by @jaytea.

---

_{Reference - What does this regex mean?}

• rexegg.com - Recursive Regular Expressions
• Regular-Expressions.info - Regular Expression Recursion