Question

I have a crawl set up:

require 'anemone'

Anemone.crawl("http://www.website.co.uk", :depth_limit => 1) do |anemone|
anemone.on_every_page do |page|
  puts page.url
end
end

However I want the spider to use a Google-analytics anti-tracking tag on every URL it visits and not necessarily actually click the links.

I could use the spider once and store all of the URL’s and use WATIR to run through them adding the tag but I want to avoid this because it is slow and I like the skip_links_like and page depth functions.

How could I implement this?

Answer 1

You want to add something to the URL before you load it, correct? You can use focus_crawl for that.

Anemone.crawl("http://www.website.co.uk", :depth_limit => 1) do |anemone|
    anemone.focus_crawl do |page|
        page.links.map do |url|
            # url will be a URI (probably URI::HTTP) so adjust
            # url.query as needed here and then return url from
            # the block.
            url
        end
    end
    anemone.on_every_page do |page|
        puts page.url
    end
end

The focus_crawl method intended to filter the URL list:

Specify a block which will select which links to follow on each page. The block should return an Array of URI objects.

but you can use it as a general purpose URL filter as well.

For example, if you wanted to add atm_source=SiteCon&atm_medium=Mycampaign to all the links then your page.links.map would look something like this:

page.links.map do |uri|
    # Grab the query string, break it into components, throw out
    # any existing atm_source or atm_medium components. The to_s
    # does nothing if there is a query string but turns a nil into
    # an empty string to avoid some conditional logic.
    q = uri.query.to_s.split('&').reject { |x| x =~ /^atm_(source|medium)=/ }

    # Add the atm_source and atm_medium that you want.
    q << 'atm_source=SiteCon' << 'atm_medium=Mycampaign'

    # Rebuild the query string 
    uri.query = q.join('&')

    # And return the updated URI from the block
    uri
end

If you’re atm_source or atm_medium contain non-URL safe characters then URI-encode them.