/ 
WWW-3172-Crawler-v0.002
/ WWW::3172::Crawler

NAME

WWW::3172::Crawler - A simple web crawler for CSCI 3172 Assignment 1

VERSION

version v0.002

SYNOPSIS

use WWW::3172::Crawler;
my $crawler = WWW::3172::Crawler->new(host => 'http://hashbang.ca', max => 50);
my $stats = $crawler->crawl;
# Present the stats however you want

METHODS

new

The constructor takes a mandatory 'host' parameter, which specifies the starting point for the crawler. The 'max' parameter specifies how many pages to visit, defaulting to 200.

Additional settings are:

  • debug - whether to print debugging information

  • ua - a LWP::UserAgent object to use to crawl. This can be used to provide a mock useragent which doesn't connect to the internet for testing.

  • callback - a coderef which gets called for each page crawled. The coderef is called with two parameters: the URL and a hashref of data. This can be used to do incremental processing, instead of doing the crawl run all at once and returning a large hashref of data. This also reduces memory requirements.

    WWW::3172::Crawler->new(
    host    => 'http://google.com',
    callback=> sub {
        my $url  = shift;
        my $data = shift;
        print "Got data about $url:\n";
        print "Stems: @{ $data->{stems} }\n";
    },
)->crawl;

crawl

Begins crawling at the provided link, collecting statistics as it goes. The robot respects robots.txt. At the end of the crawling run, reports some basic statistics for each page crawled:

  • Description meta tag

  • Keywords meta tag

  • Page size

  • Load time

  • Page text

  • Keywords extracted from page text using the following technique:

    1)

    Split page text on whitespace

    2)

    Skip stopwords

    3)

    "Normalize" to remove non-ASCII characters

    4)

    Run Porter's stemming algorithm

The data is returned as a hash keyed on URL.

Image, video, and audio are also fetched, evaluated for size and speed.

Crawling ends when there are no more URLs in the crawl queue, or the maximum number of pages is reached.

URLs are crawled in order of the number of appearances the crawler has seen. This is somewhat similar to Google's PageRank algorithm, where popularity of a page, as measured by inbound links, is a major factor in a page's ranking in search results.

AVAILABILITY

The project homepage is http://metacpan.org/release/WWW-3172-Crawler/.

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit http://www.perl.com/CPAN/ to find a CPAN site near you, or see http://search.cpan.org/dist/WWW-3172-Crawler/.

The development version lives at http://github.com/doherty/WWW-3172-Crawler and may be cloned from git://github.com/doherty/WWW-3172-Crawler.git. Instead of sending patches, please fork this project using the standard git and github infrastructure.

SOURCE

The development version is on github at http://github.com/doherty/WWW-3172-Crawler and may be cloned from git://github.com/doherty/WWW-3172-Crawler.git

BUGS AND LIMITATIONS

No bugs have been reported.

Please report any bugs or feature requests through the web interface at http://rt.cpan.org.

AUTHOR

Mike Doherty <doherty@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2011 by Mike Doherty.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.