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Gisle Aas


HTML::LinkExtor - Extract links from an HTML document


 require HTML::LinkExtor;
 $p = HTML::LinkExtor->new(\&cb, "http://www.sn.no/");
 sub cb {
     my($tag, %links);
     print "$tag @{[%links]}\n";


The HTML::LinkExtor (link extractor) is an HTML parser that takes a callback routine as parameter. This routine is then called as the various link attributes are recognized.

The HTML::LinkExtor is a subclass of HTML::Parser. This means that the document should be given to the parser by calling the $p->parse() or $p->parse_file() methods.

$p = HTML::LinkExtor->new([$callback[, $base]])

The constructor takes two optional argument. The first is a reference to a callback routine. It will be called as links are found. If a callback is not provided, then links are just accumulated internally and can be retrieved by calling the $p->links() method. The $base is an optional base URL used to absolutize all URLs found.

The callback is called with the lowercase tag name as first argument, and then all link attributes as separate key/value pairs. All non-link attributes are removed.

Returns a list of all links found in the document. The returned values will be anonymous arrays with the follwing elements:

  [$tag, $attr => $url1, $attr2 => $url2,...]

The $p->links method will also truncate the internal link list. This means that if the method is called twice without any parsing in between then the second call will return an empty list.

Also note that $p->links will always be empty if a callback routine was provided when the HTML::LinkExtor was created.


This is an example showing how you can extract links as a document is received using LWP:

  use LWP::UserAgent;
  use HTML::LinkExtor;
  use URI::URL;

  $url = "http://www.sn.no/";  # for instance
  $ua = new LWP::UserAgent;

  # Set up a callback that collect image links
  my @imgs = ();
  sub callback {
     my($tag, %attr) = @_;
     return if $tag ne 'img';  # we only look closer at <img ...>
     push(@imgs, values %attr);

  # Make the parser.  Unfortunately, we don't know the base yet (it might
  # be diffent from $url)
  $p = HTML::LinkExtor->new(\&callback);

  # Request document and parse it as it arrives
  $res = $ua->request(HTTP::Request->new(GET => $url), sub {$p->parse($_[0])});

  # Expand all image URLs to absolute ones
  my $base = $res->base;
  @imgs = map { $_ = url($_, $base)->abs; } @imgs;

  # Print them out
  print join("\n", @imgs), "\n";




Gisle Aas <aas@sn.no>