Re: Clipping ALL Occurrences of a Regex in an HTML File?

From: Chris Devers (cdevers_at_pobox.com)
Date: 02/09/05 

Date: Wed, 9 Feb 2005 15:03:28 -0500 (EST)
To: Dan Armstrong <ddarmstrong@gmail.com>

On Wed, 9 Feb 2005, Dan Armstrong wrote:

> I'm using a regular expression to extract text from an html file.

Why?

Regular expressions are really bad at analyzing complex, frequently
malformed data like HTML. Your request is an example of that: you're
matching on a very specific <font> tag, but what if the tag is
different? Legit HTML can have the tar attributes in different order, so
that tags like these are all functionally identical:

    <FONT SIZE=2 COLOR="#0000FF">
    <FONT COLOR="#0000FF" SIZE=2>
    <font size="2" color="#0000FF">
    <font size="2" color="#00F">

These would all need separate expressions, or an over-complex expression
to capture them all at once. It's painful and there's a vast number of
such quirks to account for.

Why bother fighting it this way?

You're *much* better off if you attack the problem with a proper parser,
such as HTML::Parser, HTML::SimpleParse, or HTML::TokeParser::Simple:

    <http://cpan.uwinnipeg.ca/dist/HTML-Parser>
    <http://cpan.uwinnipeg.ca/dist/HTML-SimpleParse>
    <http://cpan.uwinnipeg.ca/dist/HTML-TokeParser-Simple>

Each of these may have some small learning curve, but once you get going
with it, analyzing data like HTML gets *much* easier to do.

The path you're on now really isn't worth bothering with. Use a parser. 

-- 
Chris Devers

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