vm-list

#!/usr/bin/env ruby

require 'fileutils' 

class VmList
  @@cache_file = ENV['vm_list_cache_file'] || '/tmp/vm_list_cache'
  @@cache_ttl  = ENV['vm_list_cache_ttl']  || 60

  def self.get_vm_list
    vmware = %x{"/Applications/VMware\ Fusion.app/Contents/Library/vmrun" list | grep -v Total}.split("\n")
    vbox = %x{VBoxManage list runningvms}.split("\n")
    vmware + vbox
  end

  def self.age_of_cache?(file = @@cache_file)
    FileUtils.touch(file) unless File.exist?(file)
    Time.now - File.mtime(file)
  end

  def self.invalidate_cache
    cache_result if age_of_cache? > @@cache_ttl
  end

  def self.cache_result(file = @@cache_file)
    machines = get_vm_list

    cache = File.open(file, 'w')
    machines.each{|m| cache << m }
    cache.close
  end

  def self.get_from_cache(file = @@cache_file)
    invalidate_cache

    File.readlines(file)
  end
end

machines = VmList.get_from_cache

if ARGV.include?('-c')
  vm_word = machines.count == 1 ? "VM" : "VMs"
  puts "#{machines.count} #{vm_word}"
else
  puts machines.join("\n") unless machines.empty?
end

# vi:ft=ruby

Now with less flickering and much lower resource usage