gistfile1.rb

#!/usr/bin/ruby

instances = `ec2-describe-instances --show-empty-fields`
lines = instances.split(/\n/)
running_instances = []
lines.each do |lines|
  if lines =~ /^INSTANCE/
    fields = lines.split(/\t/)
    if fields[5] == 'running'
      running_instances << fields[1]
      running_instances << fields[4]
    end
  end
end

nodes = `knife node list`
nodes_arr = eval(nodes.gsub!(/\n/,''))
puts "deleting the following nodes from chef server :"
(nodes_arr - running_instances).each do |n|
  cmd = "knife node delete #{n} -y"
  puts "\t #{cmd}"
  puts `#{cmd}`
end