validate.rb

require 'rubygems'
require 'fog'
require 'yaml'

config = YAML::load_file(File.dirname(__FILE__) + '/config.yml')

cf = Fog::AWS::CloudFormation.new(
  :aws_access_key_id => config['key'],
  :aws_secret_access_key => config['secret']
)

template = File.open(ARGV[0], 'rb')
template_contents = template.read

begin
  response = cf.validate_template( "TemplateBody" => template_contents)
rescue Excon::Errors::BadRequest => e
  puts "Validation error: 400 Bad request"
  puts e.inspect
else
  puts "Template validated successfully."
end