20.4.1. HTML::Parser

$p = HTML::Parser->new( );

The constructor takes no arguments.

The parser object takes methods that read in HTML from a string or a file. The string-reading method can take data in several smaller chunks if the HTML is too big. Each chunk of HTML will be appended to the object, and the eof method indicates the end of the document. These basic methods are described below.

When the parse or parse_file method is called, it parses the incoming HTML with a few internal methods. In HTML::Parser, these methods are defined, but empty. Additional HTML parsing classes (included in the HTML modules or ones you write yourself) override these methods for their own purposes. For example:

package HTML::MyParser;
require HTML::Parser;
@ISA=qw(HTML::MyParser);

sub start {
     your subroutine defined here
     }

The following list shows the internal methods contained in HTML::Parser.

comment(comment)

end(tag, origtext)

start(tag, $attr, attrseq, origtext)

20.4.2. HTML::TokeParser

As we said, you should use a subclassed HTML parser if you want a better interface to HTML parsing features than what HTML::Parser gives you. HTML::TokeParser by Gisle Aas is one such example. While HTML::TokeParser is actually a subclass of HTML::PullParser, it can help you do many useful things, such as link extraction and HTML checking.

In short, HTML::TokeParser breaks an HTML document into tokens, attributes, and content, in which the HTML <a href="http://url">link</a> would break down as:

token: a
    attrib: href
content: http://url
content: link
token /a

For example, you can use HTML::TokeParser to extract links from a string that contains HTML:

#!/usr/local/bin/perl -w

require HTML::TokeParser;

# Our string that turns out to be HTML!
my $html = '<p>Some text. <a href="http://blah"My name is Nate!</a></p>';
my $parser = HTML::TokeParser->new(\$html);

get_tag( ) tells TokeParser to match a tag by name
while (my $token = $parser->get_tag("a")) {
    my $url = $token->[1]{href} || "-";
    my $text = $parser->get_trimmed_text("/a");
    print "URL is: $url.\nURL text is: $text.\n";
}

20.4.3. HTML::Element

HTML::Element objects are used to represent elements of HTML. These elements include start and end tags, attributes, contained plain text, and other nested elements.

$h = HTML::Element->new('a', 'href' => 'http:www.oreilly.com');

The new element is created for the anchor tag, <a>, which links to the URL through its href attribute.

The following methods are provided for objects of the HTML::Element class.

20.4.4. HTML::TreeBuilder

The methods provided by HTML::TreeBuilder control how the parsing is performed. Values for these methods are set by providing a Boolean value for their arguments.

20.4.5. HTML::FormatPS

$formatter = HTML::FormatPS->new('papersize' => 'Letter');

You can now give parsed HTML to the formatter and produce PostScript output for printing. HTML::FormatPS does not handle table or form elements at this time.

use HTML::FormatPS;

$html = HTML::TreeBuilder->parse_file(somefile);
$formatter = HTML::FormatPS->new( );
print $formatter->format($html);

The following list describes the attributes that can be set in the constructor:

20.4.6. HTML::FormatText

$formatter = HTML::FormatText->new(leftmargin => 10, rightmargin => 80);

The constructor can take two parameters: leftmargin and rightmargin. The value for the margins is given in column numbers. The aliases lm and rm can also be used.

The format method takes an HTML::TreeBuilder object and returns a scalar containing the formatted text. You can print it with:

print $formatter->format($html);