Regular Expression to match outer brackets

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)))

I've been trying for hours, mind you my regular expression knowledge isn't what I'd like it to be :-) so any help will be gratefully received.

Answer 1

[^\(]*(\(.*\))[^\)]*

[^\(]* matches everything that isn't an opening bracket at the beginning of the string, (\(.*\)) captures the required substring enclosed in brackets, and [^\)]* matches everything that isn't a closing bracket at the end of the string. Note that this expression does not attempt to match brackets; a simple parser (see dehmann's answer) would be more suitable for that.

Answer 2

(?<=\().*(?=\))

If you want to select text between two matching parentheses, you are out of luck with regular expressions. This is impossible.

This regex just returns the text between the fist opening and the last closing parentheses in your string.

Answer 3

Regular expressions are the wrong tool for the job because you are dealing with nested structures, i.e. recursion.

But there is a simple algorithm to do this, which I described in this answer to a previous question.

Answer 4

try this:

(?<=(?:[^(]|^))(.*)(?=[^)]|$)

group 1

Answer 5

The answer depends on whether you need to match matching sets of brackets, or merely the first open to the last close in the input text.

If you need to match matching nested brackets, then you need something more than regular expressions. - see @dehmann

If it's just first open to last close see @Zach

Decide what you want to happen with:

abc ( 123 ( foobar ) def ) xyz ) ghij

You need to decide what your code needs to match in this case.

Answer 6

I needed to get the innermost brackets... To evaluate them and substitute their results...

((?<=(?:[(]))[^(].*?(?=[)]))

Posting it here so that I an retrive it later if needed...

Answer 7

Check balancing groups, they are done for this.

Answer 8

Here is exactly how you do it:

Somewhere on the top:

using System.Text.RegularExpressions;

Then:

string Pattern = @"\((.*)\)";
Match m = Regex.Match(Input, Pattern);
Console.WriteLine("(" + m.Index + ", " + m.Length + ")" + " ---> " + m.Value);

This will match first opening with the last closing brackets.

So this will take something like "hello(sometext(some more) after text) and more) and some" will return the bold part.
A simple count of how many opening and closing brackets you have puts you one step closer to knowing if they match...