A ruby script to scrape a site for a specific dom node change. It will email you if you choose when the content changes and what the new node content changed into. Require `nokogiri` and `pony` gems. http://jackchu.com/articles/2014/01/10/web-scraping-content-changes-with-nokogiri/

web_scrape.rb

require 'nokogiri'
require 'open-uri'
require 'pony'
require 'digest'

URL = 'https://encrypted.google.com/'.freeze
CSS_SELECTOR = '#lga'.freeze
INTERVAL = 600.freeze
USER_AGENT = "Ruby/#{RUBY_VERSION}".freeze
SEND_EMAIL = false
MAIL_FROM = 'u1@example.com'.freeze
MAIL_TO = 'u2@example.com'.freeze
MAIL_OPTIONS = {
  address:               'smtp.gmail.com',
  port:                  '587',
  enable_starttls_auto:  true,
  user_name:             'user',
  password:              'password',
  authentication:        :plain, # :plain, :login, :cram_md5, no auth by default
  domain:                "localhost.localdomain" # the HELO domain provided by the client to the server
}.freeze

Pony.options = {
  from: MAIL_FROM,
  via: :smtp,
  via_options: MAIL_OPTIONS
}

target_digest = nil

while(true) do
  doc = Nokogiri::HTML(open(URL, 'User-Agent' => USER_AGENT))
  content = doc.css(CSS_SELECTOR).first
  content_digest = Digest::MD5.new.digest(content.to_s)

  if target_digest.nil?
    target_digest = content_digest
    puts "#{Time.now}: Seeded content: #{content}"
  elsif content_digest.strip != target_digest.strip
    puts "#{Time.now}: #{content}"
    Pony.mail({
      to:   MAIL_TO,
      subject: "Web Scrape Script: Target website has been updated!",
      body:  "Target URL: #{URL}\n\nChange: #{content}"
    }) if SEND_EMAIL
    target_digest = content_digest
  else
    puts "#{Time.now}: No change"
  end

  sleep INTERVAL
end