regex matching links without tag

Question

(http([s]?):\/\/?)(([a-zA-Z0-9]+(\.?))+)([a-zA-Z0-9]+((\.[a-zA-Z]{2,5}){1,2})((\/[a-zA-Z0-9\?&=_\-\~:/?#[\]@!\$&'()\*\+,;]*)*)((\.[a-zA-Z]{2,5}){0,2}))

This is my regex which is working well for matching the links in the string. But I don't want it to select every link. If a link has "> before it, or </a> after it, that link shouldn't be mathced. How can it be done?

These should be matched:

adasdas http://www.stackoverflow.com asdasas
adasdasahttp://www.stackoverflow.com/something asdas

These should NOT be matched:

adasdas<a href="somelink">           http://www.stackoverflow.com     </a>asdasas
adasdasa<a href="somelink">http://www.stackoverflow.com/something</a> asdas

Why do I need this?: I want every link to be clickable even if it isn't between anchor tags.

Could you provide some samples where the regex should pass and where not — hex494D49, Jul 09 '14 at 11:03
See also [PHP Regular expression to match keyword outside HTML tag — mario, Jul 09 '14 at 11:08
regex is not ideal for HTML parsing. U should check out a DOM parser. (http://stackoverflow.com/questions/4330545/php-html-dom-parser) — DarkBee, Jul 09 '14 at 11:08
As a note, you are missing a number of characters that can be used in valid URLs. See [this question](http://stackoverflow.com/questions/1547899/which-characters-make-a-url-invalid) for more information on valid characters. — Matthew Champion, Jul 09 '14 at 11:11
what about urls in `src=` attributes eg `img` and `script`. i really do think you need to use a propper parser, then remove all ``s from the tree and then run the regex over the `textContent` — Valerij, Jul 09 '14 at 11:15
Do you need the original string in any way? What about `strip_tags` and the scan? — hank, Jul 09 '14 at 11:18
Try this, just tested `[^href="](http([s]?):\/\/?)(([a-zA-Z0-9]+(\.?))+)([a-zA-Z0-9]+((\.[a-zA-Z]{2,5}){1,2})((\/[a-zA-Z0-9\?&=_\-\~:\/?#[\]@!\$&'()\*\+,;]*)*)((\.[a-zA-Z]{2,5}){0,2}))[^<\/a]` If this works for you than I'll paste it as an answer :) — hex494D49, Jul 09 '14 at 11:41
@Wellenbrecher According to the above this `stackoverflow.com` shouldn't be matched. Have you checked my regex? — hex494D49, Jul 09 '14 at 11:54

score 15 · Accepted Answer · edited May 23 '17 at 12:26

15

With all the disclaimers about using regex to parse html, if you want to use regex for this task, this will work:

$regex="~<a.*?</a>(*SKIP)(*F)|http://\S+~";

See the demo.

This problem is a classic case of the technique explained in this question to "regex-match a pattern, excluding..."

The left side of the alternation | matches complete <a ...tags </a> then deliberately fails, after which the engine skips to the next position in the string. The right side matches the urls, and we know they are the right ones because they were not matched by the expression on the left.

The url regex I put on the right and can be refined, just use whatever suits your needs.

Reference

edited May 23 '17 at 12:26

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answered Jul 09 '14 at 12:28

zx81

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Added my own pattern to the end of yours (`(*SKIP)(*F)|`), and it worked! Thanks. – Wellenbrecher Jul 09 '14 at 12:43
15 mins ago, my reputation score wasn't enough to vote up. But now it is 19 and I voted up. Thanks again. – Wellenbrecher Jul 09 '14 at 13:09
1

@zx81 what means (*SKIP)(*F) here? – ozahorulia Jul 20 '16 at 20:46
How to make this regex compatible with Java/Apex, initially it gives Invalid string literal error, I was able to get rid of the error by escaping some characters, but it doesn't work anymore then, any help? – Aditya Vijay Jan 22 '20 at 07:51

sMyles · Answer 2 · 2022-02-02T01:16:57.197

Here's some PHP code I combined (from answers on here) for a function to do this for emails and URLs:

function replace_links( $content ){
    $content = preg_replace('"<a[^>]+>.+?</a>(*SKIP)(*FAIL)|\b(?:https?)://\S+"', '<a href="$0">$0</a>', $content);
    $content = preg_replace('"<a[^>]+>.+?</a>(*SKIP)(*FAIL)|\b(\S+@\S+\.\S+)\S+"', '<a href="mailto:$0">$0</a>', $content);
    return $content;
}

Demo: https://glot.io/snippets/g6nwd6amyo

Most Updated: https://gist.github.com/tripflex/0cc930c2afe5f4c73f2aed61cedf95d0

score 1 · Answer 3 · edited May 23 '17 at 11:54

1

You need to add lookarounds to your regex c.f.:

edited May 23 '17 at 11:54

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answered Jul 09 '14 at 11:18

Valerij

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regex matching links without tag

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