Create a YAML mapping file for CloudFormation to select a CoreOS AMI

update-coreos-amis.sh

#!/usr/bin/ruby

require 'yaml'
require 'json'
require 'net/http'

def get_releases
  JSON[Net::HTTP.get_response(URI.parse "https://coreos.com/dist/aws/aws-stable.json").body.gsub(/,\s*\]/,"]")]
end

File.open("coreos-images.yaml","w") do |f|
f << ({
  "Mappings" => {
    "CoreosRegionImages" => get_releases.delete_if { |k,v| k == "release_info" }
  }
}).to_yaml
end