File: README

# README

Path: | README
Last Update: | Thu Nov 08 17:51:17 -0500 2007

Spider, a Web spidering library for Ruby. It handles the robots.txt, scraping, collecting, and looping so that you can just handle the data.

## Examples

### Crawl the Web, loading each page in turn, until you run out of memory

     require 'spider'
     Spider.start_at('http://mike-burns.com/') {}

### To handle erroneous responses

     require 'spider'
     Spider.start_at('http://mike-burns.com/') do |s|
       s.on :failure do |a_url, resp, prior_url|
         puts "URL failed: #{a_url}"
         puts " linked from #{prior_url}"
       end
     end

### Or handle successful responses

     require 'spider'
     Spider.start_at('http://mike-burns.com/') do |s|
       s.on :success do |a_url, resp, prior_url|
         puts "#{a_url}: #{resp.code}"
         puts resp.body
         puts
       end
     end

### Limit to just one domain

     require 'spider'
     Spider.start_at('http://mike-burns.com/') do |s|
       s.add_url_check do |a_url|
         a_url =~ %r{^http://mike-burns.com.*}
       end
     end

### Pass headers to some requests

     require 'spider'
     Spider.start_at('http://mike-burns.com/') do |s|
       s.setup do |a_url|
         if a_url =~ %r{^http://.*wikipedia.*}
           headers['User-Agent'] = "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"
         end
       end
     end

### Use memcached to track cycles

     require 'spider'
     require 'spider/included_in_memcached'
     SERVERS = ['10.0.10.2:11211','10.0.10.3:11211','10.0.10.4:11211']
     Spider.start_at('http://mike-burns.com/') do |s|
       s.check_already_seen_with IncludedInMemcached.new(SERVERS)
     end

### Track cycles with a custom object

     require 'spider'

     class ExpireLinks < Hash
       def <<(v)
         [v] = Time.now
       end
       def include?(v)
         [v] && (Time.now + 86400) <= [v]
       end
     end

     Spider.start_at('http://mike-burns.com/') do |s|
       s.check_already_seen_with ExpireLinks.new
     end

### Create a URL graph

     require 'spider'
     nodes = {}
     Spider.start_at('http://mike-burns.com/') do |s|
       s.add_url_check {|a_url| a_url =~ %r{^http://mike-burns.com.*} }

       s.on(:every) do |a_url, resp, prior_url|
         nodes[prior_url] ||= []
         nodes[prior_url] << a_url
       end
     end

### Use a proxy

     require 'net/http_configuration'
     require 'spider'
     http_conf = Net::HTTP::Configuration.new(:proxy_host => '7proxies.org',
                                              :proxy_port => 8881)
     http_conf.apply do
       Spider.start_at('http://img.4chan.org/b/') do |s|
         s.on(:success) do |a_url, resp, prior_url|
           File.open(a_url.gsub('/',':'),'w') do |f|
             f.write(resp.body)
           end
         end
       end
     end

## Author

Mike Burns mike-burns.com mike@mike-burns.com

Help from Matt Horan, John Nagro, and Henri Cook.

With `robot_rules’ from James Edward Gray II via blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/177589

[Validate]