• 0

Regex c# remove white space but not inside <pre> and </pre>


Question

Hi all

 

I am trying to write some regex to remove all white space from html.

 

but the regex i am currently using doesn't factor in that in the pre tags there maybe opening "<" and closing ">" tags

 

This matches everything inside the pre tags

 

(<)\s*?(pre\b[^>]*?)(>)([\s\S]*?)(<)\s*(/\s*?pre\s*?)(>)

 

e.g.

(009)156 (010) (0)<pre> <test> edehofo<w<dieoj >  ></pre>     yuui u    ji 

will match 

<pre> <test> edehofo<w<dieoj >  ></pre>

 

and 

(?<=\s)\s+(?![^<>]*</pre>)

 

eg will almost work but does not work if there is an "<" or ">" in the mark up.

 

space[     ]spaces <pre>[          ]spaces</pre>space[      ]spaces 

 

will result in 

space[ ]spaces <pre>[ ]spaces</pre>space[ ]spaces 

 

but if there is a "<" or ">" in the pre tags then it will not work.

 

Could anyone help me

 

 

 

 

 

 

 

 

 

 

10 answers to this question

Recommended Posts

  • 0

A warning: http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags

 

A solution: http://stackoverflow.com/questions/8762993/remove-white-space-from-entire-html-but-inside-pre-with-regular-expressions (same as your regex)

 

Just be careful with regex and HTML, parsing it to a C# object and then outputting it without whitespace is probably a better way to do this (likely to be slower though).

 

You shouldn't include < or > in <pre>, they should be escaped to &lt; and &gt;

  • 0

Thanks, but I've already been to those sites and a lot of others trying to find an solution.

 

From that its highlighted that I maybe able to do it in to step then...

 

1. encode all html with in pre tags

2. then use (?<=\s)\s+(?![^<>]*</pre>) to remove white space.

 

I am finding it hard to now find regex which will encode html with in a pre tag.

I love cats and dogs but dogs > than cats

<spaces>       <spaces>
<pre>
    1 > 0  = ?

    <code>       dedw</code>
</pre>

should be 

I love cats and dogs but > than cats <spaces> <spaces>
<pre>
    1  &gt; 0 = ?
    &glt;code&gt;       dedw &gt;/code &gt;
</pre>

It would be easier if i had some regex which basically ignored everything between a given tag.

 

I am doing my own research and trying to find the answer... but thought i would clarify what I am trying to do.

 

Thanks if you can help me find a solution

  • 0

Hi Eric

 

I'm trying to do it for c#

 

Basically I can get what i want if I can strip out white-space but not between two sets of chars

 

e.g.  <pre> anything </pre> or <code> anything </code>

 

seems more challenging that i thought it would be.

 

 (?<=\s)\s+(?![^<>]*</pre>)  is awesome but if i could get it to basically ignore everything inside of a given tag

 

My understanding of how to get the right syntax for regex is limited.

 

Match everything but not between tag(pre or code) and remove white space.

 

any help with getting this to work would be so awesome.

  • 0

How about the following: http://snipd.net/parsing-xhtml-into-a-dom-tree-in-c

You avoid using regex as you simply parse then print the HTML instead.

 

 

You might also want to re-read my first link, which points out that you cannot parse arbitrary (X)HTML using a regex. It is not possible as regex is not powerful enough to parse (X)HTML. (Parsing a limited subset is possible)

  • 0

to anyone who is good with regex please help

 

(?<=\s)\s+(?![^[<p]+?[e>])

 

cant not get this to work but must be close?

 

to: Lant

 

Sorry but i don't need to parse the HTML... i am not trying to validate it or read it really... 

 

I am wanting to remove white space but only when outside of a given tag like say <pre> or <code>

 

It has been working fine with (?<=\s)\s+(?![^<>]*</pre>)  until i hit a new requirement which.... is that the <pre> tag can contain < or >

 

which this regex does not support. One suggestion was to replace < and > with their HTML versions &lt; and &gt;

 

but again i would need to have something which only applied this on html with in tag the <pre> tag and I would need to do it in c#

 

seems easier to just get the regex to ignore things between tags some how...

 

Thanks

  • 0

If you don't mind doing the replace in C#, you can use capture groups with this pattern.

(?:\<pre\>)(.*)(?:\<\/pre\>)

It should capture everything between the pre tags and the value of the capture can then be string.Replaced on. I am working on a Regex replace version so you can use RegexOptions.Compiled. This regex was tested with CaseInsensitive and SingleLine (despite it being multi-line, using that to adjust how it handles .*)

 

1cKDh7e.png

 

 

so for example:

 

private static Regex preBlockMatch = new Regex(@"(?:\<pre\>)(.*)(?:\<\/pre\>)", RegexOptions.Compiled | RegexOptions.Singleline | RegexOptions.IgnoreCase);

 

(code block)

string newValue = preBlockMatch.Captures[0].Value.Replace("<", "&lt;");

(code block)

 

obviously room for some enhancement but it gets you started

  • 0

Thought I would share what I got working......

 

Also thanks!!! to Squirrelington for the regex for the between stuff

 public class MinifiedStream : MemoryStream
        {
            private readonly Stream _output;
            public MinifiedStream(Stream stream)
            {
                _output = stream;
            }

            private static readonly Regex Whitespace = new Regex(@"(?<=\s)\s+(?![^<pre>]*</pre>)",RegexOptions.Compiled);

            private static readonly Regex PreBlockMatch = new Regex(@"(?:\<pre\>)(.*)(?:\<\/pre\>)", RegexOptions.Compiled | RegexOptions.Singleline | RegexOptions.IgnoreCase);

            Dictionary<string, string> result = new Dictionary<string, string>();

            public override void Write(byte[] buffer, int offset, int count)
            {
                var html = Encoding.UTF8.GetString(buffer);

                //------------------------------------
                var matches = PreBlockMatch.Matches(html);
                int loopcount = 1;
                foreach (Match match in matches)
                {
                    var token = Guid.NewGuid().ToString() + "_"+ loopcount;
                    html = html.Replace(match.Value, token);
                    result.Add(token, match.Value);
                    loopcount ++;
                }
                //------------------------------------



                html = Whitespace.Replace(html, string.Empty);
                html = html.Trim();

                //-----------------------------------
                foreach (var match in result)
                {
                    html = html.Replace(match.Key, match.Value);
                }

                //-----------------------------------

                _output.Write(Encoding.UTF8.GetBytes(html), offset, Encoding.UTF8.GetByteCount(html));
            }
        }

But still feels as if you should be able to create a straight regex version.

 

if anyone can help me improve that would be awesome

  • 0

I agree that there should be a way to get it exclusively in regex but I am only really good at matching things, I don't have a lot of experience in replacement syntax. I know you can do $1 for the first group, $2 for 2nd or ${name} for named groups but how to modify the contents of those groups in the replacement is beyond me atm. Maybe someone with more experience will be able to chime in. :) Glad it is working thus far though. \o/

 

btw the regex I gave you, I probably went a little too crazy with the non-capture groups. I think at the time I was trying some funky magic to try and capture parts of it for replacement purposes but ended up with that.

<pre>(.*)</pre>

would probably be fine as well. lol

This topic is now closed to further replies.
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Posts

    • Free Download Manager 6.28.1.6321 by Razvan Serea Free Download Manager is a powerful, easy-to-use and absolutely free download accelerator and manager. FDM accelerates downloads by splitting files into sections and then downloading them simultaneously. As a result download speed increases up to 600%, or even more! FDM can also resume broken downloads so you needn`t start downloading from the beginning after casual interruption. FDM lets you download files and whole web sites from any remote server via HTTP, HTTPS and FTP. You can also download files using BitTorrent protocol. In addition, Free Download Manager allows you to: adjust traffic usage; to organize and schedule downloads; download video from video sites; download whole web sites with HTML Spider; operate the program remotely, via the internet, and more! Free Download Manager is compatible with the most popular browsers Google Chrome, Firefox, Microsoft Edge, Internet Explorer and Safari. Free Download Manager 6.28.1.6321 changelog: Improved add-ons support. Improved M3U support. Fixed: crash bug in BitTorrent module. Fixed: minor bugs. Windows: a bit improved installer. Windows: Firefox bug workaround. Android: Qt updated to 6.9.1. Download: Free Download Manager (64-bit) | 45.8 MB (Freeware) Links: Home Page | Linux, Mac, Android | MS Store | Screenshot Get alerted to all of our Software updates on Twitter at @NeowinSoftware
    • Tariffs have nothing to do with this pricing. It was always intended to be slightly more expensive then the S25+
    • Hello, The static link still downloads 10.3.2040.0 from May 22, 2025. The 10.3.2412.0 version can be downloaded directly from emclient.com/dist/v10.3.2412/setup.msi. Regards, Aryeh Goretsky
    • Hello, Yes, and yes. More specifically, there are lots of features in Windows that I do not use--I cannot recall the last time I needed to run EUDCEDIT.EXE or ODBCAD32.EXE on a computer I own, but I'm sure that for some people they are useful, and for a smaller set of people they might even be indispensable. I don't begrudge Microsoft for including them as part of the standard Windows installation nor the people who need such tools; sometimes it is convenient to have some little utility or feature readily available. One thing I do begrudge is Microsoft's over-reliance on its own telemetry, and perhaps surpisingly on the flip side, customers who disable it. Collecting telemetry is generally a good thing, if it is done for good reasons and does not include any customer PII. However, how you interpret that telemetry is even more important, as that can lead to all sorts of disastrous decisions. On the customer side of things, telemetry is your "vote:" it's how you tell companies what features you use in the program, and lets them prioritize things appropriately. One glaring example is Windows 8, which shipped with the full-screen Start Screen because Microsoft's telemetry told them the average Windows user pressed the Windows key to bring up the Start Menu less than once a day. I have often wondered how many "power users" of previous versions of Windows (XP, Vista, and 7) that relied on the Start Menu disabled the telemetry that would have told Microsoft a difference story about its usage. More recently, I came across a young lady who had a problem with a third-party sync program on her computer running Windows 7. An update for the utility removed Windows 7 compatibility, and broke her backup process. Now, support for Windows 7 ended over 5 years ago in 2020, but there are ISVs who still support their software on it, but decisions about stuff like that are made, in part, by knowing what percentage of your customer base is on what operating system version. When I asked about that, she mentioned she had specifically disabled the telemetry from the sync program to its developers, which was optional to begin with. What made things even worse was that this was an open source utility, and its authors had a very clear, well-designed and scoped policy on the telemetry they collected, the pains they went through to avoid collecting any PII, and even other ancillary risks involving information disclosure (like just using of the software) because of the network connection made for the checks. Yet, she took herself out of telling the project maintainers "Hey, I use your software and I'm running Windows 7" by disabling the telemetry checks, which could have let them know they needed to continue supporting it. In a sense, sending telemetry is just like voting: Individually, you may not think it matters much, but it is often the basis for very important decisions. Regards, Aryeh Goretsky
    • Hello, My thoughts on this are mixed. Microsoft has hosted malicious code in the Microsoft Update Catalog where third party device drivers are stored; I wrote about one such incident about fifteen years ago, so if there are any other old malicious drivers floating around in the catalog, this will be a good step towards preventing any infestations from reoccurring. Another thing, which surprisingly is not mentioned in Microsoft's announcement, is that this helps protect against BYOVD (Bring Your Own Vulnerable Driver) attacks, where malware either comes with or downloads an older device drivers with vulnerabilities in it that can be exploited to gain access to kernel memory. Removing all those old device drivers from the Windows Update Catalog, potentially with all sorts of undisclosed vulnerabilities in them, means an attacker can no longer leisurely count on being able to download them from Microsoft's servers--something that may go unnoticed or ignored by security analysts. This makes the adversary attack a little more noisy, since they have to either include the device driver with the rest of their initial payload or download it from a third-party site at some point prior to beginning their BYOVD attack. On the other hand, it means that people who are looking for a specific version of an older device driver for whatever legitimate reasons, like compatibility, performance or stability, may end up going to dodgy third-party sites in search of older drivers, which increases the risk of exposure to everything from nuisance advertisements and unwanted software to actual malicious code. As for me, I have keeping copies of all the device drivers, firmware updates, etc. I have downloaded over the years, some dating back to DOS and Windows 3.x era, not just for hardware I won, but popular things like unified chipset and video card drivers, just in case I ever needed it. It might seem silly to collect such a thing, but the hardware drivers, firmware updates, and documentation are just about 2 TB in size. From my perspective, it is an inexpensive form of insurance, especially given that disk space is always getting cheaper over time. Regards, Aryeh Goretsky
  • Recent Achievements

    • Contributor
      GravityDead went up a rank
      Contributor
    • Week One Done
      BlakeBringer earned a badge
      Week One Done
    • Week One Done
      Helen Shafer earned a badge
      Week One Done
    • First Post
      emptyother earned a badge
      First Post
    • Week One Done
      Crunchy6 earned a badge
      Week One Done
  • Popular Contributors

    1. 1
      +primortal
      660
    2. 2
      ATLien_0
      266
    3. 3
      Michael Scrip
      235
    4. 4
      Steven P.
      164
    5. 5
      +FloatingFatMan
      149
  • Tell a friend

    Love Neowin? Tell a friend!