http://qs321.pair.com?node_id=336560


in reply to Cutting Out Previously Visited Web Pages in A Web Spider

Here's my pretty simple try (without using files and just for a single page). Adjust to taste: 

#!/usr/bin/perl

use strict;
use warnings;

use LWP::RobotUA;
use HTML::SimpleLinkExtor;

sub grab_links {

  my ( $ua, $url ) = @_;

  my @links;
  my $response = $ua->get($url);

  if ($response->is_success) {
    my $extor   = HTML::SimpleLinkExtor->new();
    my $content = $response->content;

    $extor->parse($content);
    @links = $extor->a;   # get a ref links. Check docs - these are re
+lative paths.

  } else {
    die $response->status_line;
  }

  return @links;
}

my $visit = $ARGV[0];

my $ua = LWP::RobotUA->new('my-robot/0.1', 'me@foo.com');  # Change th
+is to suit.
$ua->delay( 0.1 );  # hit every 1/10 second

my @links = grab_links($ua, $visit);

my %uniq;

foreach ( @links ) {
  $uniq{$_}++;
}

print "Visited: ", $visit, " found these links:\n", join( "\n", keys %
+uniq), "\n";

[download]

Update: this code was put here after talking to mkurtis in the CB. It appears to do most of the things mkurtis is after, so I posted it for future reference.
Most of the code was taken straight from the docs for HTML::SimpleLinkExtor, LWP::RobotUA and LWP::UserAgent.

This is the first time I've used any of those modules and it was quite cool :-)

If the information in this post is inaccurate, or just plain wrong, don't just downvote - please post explaining what's wrong.
That way everyone learns.

Replies are listed 'Best First'.
Re: Cutting Out Previously Visited Web Pages in A Web Spider
by mkurtis (Scribe) on Mar 15, 2004 at 03:58 UTC
    Thanks kappa and BazB, Would you by any chance know how to use URI::URL to make all links absolute. I believe the syntax in this case would be

    url("links from extor")->abs("$url");

    [download]
    But I don't see how to put this in the do loop.

    Because CPAN isn't searching, heres the URI link: URI::URL

    thanks a bunch

[reply]
[d/l]

      There's no need to use URI::URL. Change the HTML::SimpleLinkExtor code to return absolute instead of relative paths.

      There is a comment in my code in my last reply noting that my code currently returns relative paths and pointing you to the module docs. RTFM :-)

      If the information in this post is inaccurate, or just plain wrong, don't just downvote - please post explaining what's wrong.
      That way everyone learns.
[reply]
        I have been trying to build in your error checking, as well as tie it into a DBM for when it crashes. Heres what I got: 
        #!/usr/bin/perl -w
use strict;
use warnings;

use LWP::RobotUA;
use HTML::SimpleLinkExtor;

use vars qw/$http_ua $link_extractor/;

sub crawl {
    my @queue = @_;
    my %visited;
    my $a = 42464;
    my $base;
    dbmopen(%visited, "visited", 0666);
    while ( my $url = shift @queue ) {
        next if $visited{$url};

        my $response = $http_ua->get($url);
    if ($response->is_success) {
        my $content = $response->content
            open FILE, '>' . ++$a . '.txt';
            print FILE "$url\n";
        print FILE $content;
            close FILE;

            print qq{Downloaded: "$url"\n};

            push @queue, do {
                    my $link_extractor = HTML::SimpleLinkExtor->new($u
+rl);
                    $link_extractor->parse($content);
                    $link_extractor->a;

            };
        $visited{$url} = 1;
    } else {
        dbmclose(%visited);
            die $response->status_line;
      }
    }  
    
}

$http_ua = new LWP::RobotUA theusefulbot => 'bot@theusefulnet.com';
$http_ua->delay( 10 / 6000 );

crawl(@ARGV);

        [download]
        This gives me: Can't call method "is_success" without a package or object reference at theusefulbot.pl line 21.

        Any Ideas?

        Thank you

[reply]
[d/l]

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