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regexparenthesesopenrefinegrel

Remove outermost parentheses

I am having problem while removing outermost parentheses from a string using GREL. What i am trying to do is simply remove outermost parentheses and all other parentheses should be kept intact. Below is what i am trying to do using regex -

value.split(/(abc+/)

and below is my sample string that i am trying to parse and desired output.

Foo ( test1 test2 ) => Foo test1 test2
Bar ( test1 t3() test2 ) => Bar test1 t3() test2
Baz ((("Fdsfds"))) => Baz (("Fdsfds"))

I would appreciate any help.

Solution

  • One option could be to use a capturing group and in the replacement use the first capturing group.

    Note that this does not take balanced parenthesis into account.

    It matches the outer parenthesis, then captures in a group what is inside and matches an outer parenthesis again.

    Inside the capturing group is an alternation that matches not () or from an openening till closing parenthesis.

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

    Explanation

    • \( Match outer parenthesis (
    • ( Capture group -\(* Match 0+ times (
      • (?: Non capturing group
        • [^)(]* Match 0+ times not ( or )
        • | Or
        • \([^)]*\) Match from ( till next ) closing parenthesis
      • )* Close non capturing group and repeat 0+ times
      • \)* Match 0+ times a closing parenthesis
    • ) Close capture group
    • \) Match outer closing parenthesis

    Regex demo