Regex replace urls with tag

Question

In html need replace url to tag

Only http://google3.com:1139 and http://google6.com:1139

<div>
  <a href="http://google1.com:1139" target="_blank">http://google2.com:1139</a> 
  http://google3.com:1139
</div>
<div>
  <a href="http://google4.com:1139" target="_blank">http://google5.com:1139</a>
  http://google6.com:1139
</div>

Must be

<div>
  <a href="http://google1.com:1139" target="_blank">http://google2.com:1139</a> 
  <a href="http://google3.com:1139" target="_blank">http://google3.com:1139</a> 
</div>
<div>
  <a href="http://google4.com:1139" target="_blank">http://google5.com:1139</a>
  <a href="http://google6.com:1139" target="_blank">http://google6.com:1139</a> 
</div>

I found solution

        var result = Regex.Replace("<div><a href=\"http://google1.com:1139\" target=\"_blank\">http://google2.com:1139</a>http://google3.com:1139</div><div><a href=\"http://google4.com:1139\" target=\"_blank\">http://google5.com:1139</a>http://google6.com:1139</div>", 
                                   @"((?<!href=['""]?)(http|ftp|https):\/\/[\w\-_]+(\.[\w\-_]+)+([\w\-\.,@?^=%&amp;:/~\+#]*[\w\-\@?^=%&amp;/~\+#])?)",
                                   "<a target='_blank' href='$1'>$1</a>");

But need replace

started with http but now with href="http (found)
not ended with

</a>

or skip between

<a ... </a>

Maybe you need simpler expression? [Like This](https://regex101.com/r/f1fbC5/1) — CommonSense, Mar 10 '17 at 11:32
@CommonSense May be. I need replace http://google3.com:1139 and http://google6.com:1139 to template $1 — Alexandr Sulimov, Mar 10 '17 at 11:39
If it is only these two, why not simply use `string.replace("http://google3.com:1139","http://google3.com:1139");`? And same for google6... — Fildor, Mar 10 '17 at 11:45
If it only shall be done when it occurs as child of
better use XML parsing and XPath than Regex. — Fildor, Mar 10 '17 at 11:47
After edit: I'd use XPath to get all Text-Children of divs, then check the Text Value if it matches your urls and if so replace the textnode with a new anchor node accordingly. Maybe have a look into **Linq to XML**. — Fildor, Mar 10 '17 at 11:53

score 1 · Accepted Answer · answered Mar 10 '17 at 11:48

I take it the requirements may be rephrased as follows:

everything between <a and </a> should be left intact (this includes href attribute values)
any URLs of the given pattern outside the <a and </a> should be wrapped in anchor tags.

This may be achieved by searching two patterns, <a.*?</a> and <some URL>, as alternatives. Then replace the match by itself if the first pattern is found and by a wrapped URL if the second pattern found:

Regex.Replace(html,
    @"<a.*?</a>|(?:https?|ftp)://[\w_.-]+:\d+",
    m => m.Value.StartsWith("<") 
        ? m.Value
        : string.Format("<a target='_blank' href='{0}'>{0}</a>", m.Value));

Demo: https://ideone.com/Jq1s8y

P.S.

I simplified the URL regex for the sake of conciseness. The real application may require more extended pattern.

Regex replace urls with tag

1 Answers1