c# - regular expression for finding 'href' value of a <a> link

Question

I need a regex pattern for finding web page links in HTML.

I first use @"(<a.*?>.*?</a>)" to extract links (<a>), but I can't fetch href from that.

My strings are:

1. <a href="www.example.com/page.php?id=xxxx&name=yyyy" ....></a>
2. <a href="http://www.example.com/page.php?id=xxxx&name=yyyy" ....></a>
3. <a href="https://www.example.com/page.php?id=xxxx&name=yyyy" ....></a>
4. <a href="www.example.com/page.php/404" ....></a>

1, 2 and 3 are valid and I need them, but number 4 is not valid for me (? and = is essential)

---

Thanks everyone, but I don't need parsing <a>. I have a list of links in href="abcdef" format.

I need to fetch href of the links and filter it, my favorite urls must be contain ? and = like page.php?id=5

Thanks!

question from:https://stackoverflow.com/questions/15926142/regular-expression-for-finding-href-value-of-a-a-link

Answer 1

I'd recommend using an HTML parser over a regex, but still here's a regex that will create a capturing group over the value of the href attribute of each links. It will match whether double or single quotes are used.

<as+(?:[^>]*?s+)?href=(["'])(.*?)1

You can view a full explanation of this regex at here.

Snippet playground:

const linkRx = /<as+(?:[^>]*?s+)?href=(["'])(.*?)1/;
const textToMatchInput = document.querySelector('[name=textToMatch]');

document.querySelector('button').addEventListener('click', () => {
  console.log(textToMatchInput.value.match(linkRx));
});

<label>
  Text to match:
  <input type="text" name="textToMatch" value='<a href="google.com"'>
  
  <button>Match</button>
 </label>