exchange-rates.rb

#!/usr/bin/env ruby
# encoding: utf-8

require "open-uri"
require "nokogiri"

# Configuration.
URL = "http://www.xe.com/ucc/convert/?Amount=1&From=GBP&To=%s"
EMAIL = "[email protected]"
NOTIFY_IF = {CZK: 30, EUR: 1.19}
CURRENCIES = NOTIFY_IF.keys

# Helpers.
def notify(email, currency, rate)
  system("echo '' | mail #{email} -s '1 #{currency} is #{rate} today!'")
end

# Main.
CURRENCIES.each do |currency|
  open(URL % currency) do |stream|
    document = Nokogiri::HTML(stream.read)
    data = document.css("table.Cnvrsn tr.CnvrsnTxt").inner_text.gsub(/\s+/m, " ")
    data.match(/1.00 GBP = ([\d\.]+)/) do |match|
      rate = match[1].to_f
      puts "~ 1 #{currency} is #{rate} today."
      notify(EMAIL, currency, rate) if rate > NOTIFY_IF[currency]
    end
  end
end