gistfile1.rb

#!/usr/bin/ruby

query = ARGV[0]
if query.nil?
  warn "usage: #{$0} classname"
  exit 1
end
require "puppet"
Dir.glob("/var/lib/puppet/yaml/node/*yaml").each do |node|
  yaml = YAML.load_file node
  puts yaml.name if yaml.classes.include?(query)
end