Re: Stripping HTML tags

[Philippe Lhoste <PhiLho@...>]

Florian Berger wrote:
> I thought that stripping HTML tags was easy until I saw something like 
> this:
> <a href="http://www.example.com"; alt="> example"> example </a>

I believe this is not correct HTML code, even by old pre-XHTML 
standards. It should be alt="&gt; example".
I am not sure this is valid XML, although I believe XML is more strict 
on encoding & and < than on >.

Of course, the problem is that browsers are quite tolerant on this kind 
of error (IMHO, there should have been stricter to start with, the Web 
would be much more clean...), so are likely to find these constructs in 
real pages.

> My code was:
> local s = '<a href="http://www.example.com"; alt="> example"> example </a>'
> s = string.gsub(s, '<.->', ' ')
> print(string.gsub(s, '<.->', ' '))
>
> -> example"> example
>
>
> I have seen some examples using PHP and regular expressions. Programming 
> in Lua 20.1 says that Lua cannot do all what POSIX implementation does 
> (http://www.lua.org/pil/20.1.html). Can this be done in Lua? All that come 
> to my mind are captures but I'm not sure if they help at all.  Of course 
> my example works in most of the cases, but it would be nice to have it 
> work even better.

Note there is a PCRE wrapper for Lua, if you need more powerful RegExp.
If, of course, you are not stuck with standard Lua.

Looking at other answers, I don't think an XML parser would do the job. 
Regular HTML isn't even XML compliant, so an XML parser would complain 
about unclosed tags like <br> or <p>.

A full tokeniser/parser could be a solution, perhaps too costly for your 
need... HTML isn't really easy to parse, even more if you have to be as 
tolerant to errors as the browsers are... (like the above, accepting -- 
in comments, raw & in text, etc.).

--
Philippe Lhoste
--  (near) Paris -- France
--  http://Phi.Lho.free.fr
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