Regular Expression to find a string included between two characters while EXCLUDING the delimiters

Easy done:

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

Technically that's using lookaheads and lookbehinds. See Lookahead and Lookbehind Zero-Width Assertions. The pattern consists of:

• is preceded by a [ that is not captured (lookbehind);
• a non-greedy captured group. It's non-greedy to stop at the first ]; and
• is followed by a ] that is not captured (lookahead).

Alternatively you can just capture what's between the square brackets:

\[(.*?)\]

and return the first captured group instead of the entire match.

If you are using JavaScript, the solution provided by cletus, (?<=\[)(.*?)(?=\]) won't work because JavaScript doesn't support the lookbehind operator.

Edit: actually, now (ES2018) it's possible to use the lookbehind operator. Just add / to define the regex string, like this:

var regex = /(?<=\[)(.*?)(?=\])/;

Old answer:

Solution:

var regex = /\[(.*?)\]/;
var strToMatch = "This is a test string [more or less]";
var matched = regex.exec(strToMatch);

It will return:

["[more or less]", "more or less"]

So, what you need is the second value. Use:

var matched = regex.exec(strToMatch)[1];

To return:

"more or less"

You just need to 'capture' the bit between the brackets.

\[(.*?)\]

To capture you put it inside parentheses. You do not say which language this is using. In Perl for example, you would access this using the $1 variable.

my $string ='This is the match [more or less]';
$string =~ /\[(.*?)\]/;
print "match:$1\n";

Other languages will have different mechanisms. C#, for example, uses the Match collection class, I believe.

[^\[] Match any character that is not [.

+ Match 1 or more of the anything that is not [. Creates groups of these matches.

(?=\]) Positive lookahead ]. Matches a group ending with ] without including it in the result.

Done.

[^\[]+(?=\])

Proof.

http://regexr.com/3gobr

Similar to the solution proposed by null. But the additional \] is not required. As an additional note, it appears \ is not required to escape the [ after the ^. For readability, I would leave it in.

Does not work in the situation in which the delimiters are identical. "more or less" for example.