tracking changes over time, simple example

track.rb

require 'open-uri'
require 'yaml/store'
require 'nokogiri'

doc = Nokogiri(open('http://namebit.org'))
current = doc.at('#blocks_found').text.to_i

YAML::Store.new('namebit.yaml').transaction do |store|
  if previous = store[:previous]
    case current <=> previous
    when 1
      puts "It increased! Up from #{previous} to #{current}"
    when 0
      puts "No change, it's still #{current}"
    when -1
      puts "It decreased! Down from #{previous} to #{current}"
    end
  else
    puts "First time, it's at #{current} right now"
  end

  store[:previous] = current
end