Check for canonical URLs from a submitted link.

Submitted Link Canonical URL Checker

# http://kellishaver.tumblr.com/post/54922678930/quick-tip-canonical-urls
# Building a site that handles link submissions? Check submitted links for a canonical URL tag to avoid duplicates.
# Similarly, if you’re a content creator and you’re not using the canonical URL tag, you should be!

def canonical(url)
  begin
    page = Nokogiri::HTML(open(url))
    page.css("link[rel=canonical]")[0]["href"]
  rescue
    url
  end
end