Remove whitespace except in pre tags

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I have a replacing regular expression to remove whitespace from a HTML document: /\s\s+/

Is there a way to remove all whitespace except from within pre tags?

eg.

<html>
<head>
	<title>Rawr</title>
</head>
<body>

<pre>
	Some stuff
</pre>

</body>
</html>

To look like this:

<html><head><title>Rawr</title></head><body><pre>
	Some stuff
</pre></body></html>

Is this even possible?

Posted 13-Jan-10 10:53am

fly904

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Rick Shaub · Accepted Answer · 2010-01-13T11:00:00

Solution 1

Can't you do it in two steps? In other words, remove the whitespace and then replace "<pre>" with "<pre>\n" and "</pre>" with "\n</pre>".

Posted 13-Jan-10 11:00am

Rick Shaub

AspDotNetDev · Accepted Answer · 2010-01-16T09:09:00

You can find all whitespace that does not exist after an opening PRE (that isn't followed by a closing PRE) and that does not exist before a closing PRE (that isn't preceeded by an opening PRE). That would require a negative lookahead and a negative lookbehind that themselves contain a negative lookahead and a negative lookbehind. I've never tried combining negative lookaheads/lookbehinds like that, so I'm not sure it would work, but it seems like that would be the way to go. I'll let you figure out the regex, but pseudo-regex would be something like this:

(must not contain a PRE that is not followed by a /PRE)
(?<=(.|\n)*)
whitespace
(?=(.|\n)*)
(must not contain a /PRE that is not preceeded by a PRE)

Here is what a negative lookbehind looks like:

(?<!\<PRE\>)

Here is what a negative lookahead looks like:

(?!\<\/PRE\>)

You'll have to do some testing to play with the nesting, as I am not quite sure how that works.

Check out this reference for more C# regex help.