Combining Regex 'in between' AND 'do not contain'

Question

I've tried to combine two Regex with AND but failed at the attempt.

Pick up anything between '[[' and (']]' or '|') in direct succession :

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

Doesn't contain 'http' :

^(?:(?!http).)*$

My best try was

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

Following https://stackoverflow.com/a/870506 but it is not working.

My goal is to get all the intenal links in a dokuwiki page typically : 'my_page', 'my_other_page', but not 'http://your_page' in :

[[my_page]]

[[my_other_page|this is my other page]]

[[http://your_page|this is your page]]

Try `\[\[(?!https?:\/\/)[^][|]*(?:\|[^][]*)?]]`, see [this regex demo](https://regex101.com/r/uEyJAP/1). — Wiktor Stribiżew, Mar 24 '21 at 22:36
Can you just apply one regex after the next in your code? Sometimes that's easier than coming up with a Super RegEx... — xdhmoore, Mar 24 '21 at 22:41
Thanks but I need to get rid of the brackets as well I want to match 'my_page' and 'my_other_page' only. — FractalCitta, Mar 24 '21 at 22:41
Yes I thought about that : applying another regex afterward. but the first result would be store in an array and so I would have to do loop to all the results and check them, a bit more ugly, but I can do that. — FractalCitta, Mar 24 '21 at 22:43
Is it OK for http to exist outside the delimiters? eg `[[my_other_page|foo http bar]]` should match `my_other_page`? Does matching input always start/end with delimiters? — Bohemian, Mar 24 '21 at 22:47
To @Bohemian, yes it is ok. In dokuwiki all external link start by http in between '[[' and (']]' or '|') . If there is no http it means it is an internal link. So [[my_other_page|foo http bar]] should match my_other_page. — FractalCitta, Mar 24 '21 at 22:52

score 1 · Answer 1 · answered Mar 24 '21 at 22:54

Then use

(?<=\[\[)(?!https?:\/\/)[^][|]+
(?<=\[\[)(?!https?:\/\/)[^][|]+(?=(?:\|[^][]*)?]])

See the regex demo

Details:

(?<=\[\[) - a positive lookbehind that matches a location immediately preceded with [[
(?!https?:\/\/) - a negative lookahead that cancels the match if there is http:// or https:// immediately to the right of the current location
[^][|]+ - one or more chars other than ], [ and |
(?=(?:\|[^][]*)?]]) - a positve lookahead that requires the following sequence of patterns immediately to the right of the current location:
- (?:\|[^][]*)? - an optional occrurrence of a | and then any zero or more chars other than [ and ]
- ]] - a ]] string.

NOTE: Depending on the regex flavor, you may need to escape ] or/and [ chars in the character class, i.e. [^][] => [^\][] (JavaScript RegExp) or [^\]\[] (Java, Ruby).

The fourth bird · Accepted Answer · 2021-03-24T23:53:49.790

As an alternative, you could make use of a SKIP FAIL approach:

\[\[https?:\/\/(*SKIP)(*FAIL)|\[\[\K[^][|]+

The pattern matches:

\[\[https?:\/\/ Match [[https:// with optional s
(*SKIP)(*FAIL) Consument the characters that you want to avoid
| Or
\[\[\K Match [[ and forget what is matched so far
[^][|]+ Match 1+ times any char except ] [ or |

Regex demo

$strings = [
    "[[my_page]]",
    "[[my_other_page|this is my other page]]",
    "[[http://your_page|this is your page]]",
];

$re = '/\[\[https?:\/\/(*SKIP)(*FAIL)|\[\[\K[^][|]+/';

foreach ($strings as $s){
    if (preg_match($re, $s, $matches)) {
        var_dump($matches[0]);
    }    
}

Output

string(7) "my_page"
string(13) "my_other_page"

To verify the optional part with | and the closing ]] you can use a negative lookahead

\[\[https?:\/\/(*SKIP)(*FAIL)|\[\[\K[^][|]+(?=(?:\|[^][]*)?]])

Regex demo

Or if the last part can also contain ] or [

\[\[https?:\/\/(*SKIP)(*FAIL)|\[\[\K[^][|]+(?=(?:\|.*?)?]])

Regex demo

score 0 · Answer 3 · answered Mar 24 '21 at 22:48

0

Here is the Regex Pattern with some adjustments to Wiktor Stribiżew's answer in the comment section. By using lookahead and lookbehind, you can deselect the brackets.

(?<=\[\[)(?!https?:\/\/)[^][|]*(?:\|[^][]*)?(?=]])

answered Mar 24 '21 at 22:48

1

Almost perfect thank you very much. It just grabs '| this is my other page' and I would like to not have it. The goal is to have only the first part of what follows '[[' and not what is after '|' if there is one. I have to admit that I don't understand much about all of this regex, but thank you so much – FractalCitta Mar 24 '21 at 22:56

Combining Regex 'in between' AND 'do not contain'

3 Answers3