trivial demo to save timestamp in a file

since.rb

#!/usr/bin/env ruby
require 'date'
require 'yaml'

now = DateTime.now
puts 'time is now %s' % now

my_hash = Hash.new
my_hash['last_update'] = now.iso8601

path = '/tmp/boogabooga.yaml'

# save my time
File.open(path, 'w') do |f|
  f.puts my_hash.to_yaml
end

# sleep 5 seconds
5.times {print '.'; sleep 1}
puts ''

# read it back
y = YAML.load_file(path)
puts 'time is now %s' % DateTime.now.iso8601
puts 'but last update was %s' % y['last_update']