wmi-lite is a lightweight Ruby gem utility library for accessing basic Windows Management Instrumentation (WMI) functionality on Windows. It has no dependencies outside of the Ruby interpreter and libraries and of course the Windows operating system.


To install it, run:

gem install wmi-lite


To use wmi-lite in your Ruby source code, just require it:

require 'wmi-lite'

You can then instantiate an object through WmiLite::Wmi.new that will allow you to query a WMI namespace by calling methods on that object.

  • The default namespace if no argument is specified to new is root\cimv2. To override, pass the desired WMI namespace string as an argument to the constructor.
  • To execute queries against the object's namespace, use the instances_of, first_of, and query methods.
  • The instances_of method will return all instances of a given class in the namespace as an array of instances.
  • The query method returns the results of an arbitrary WMI Query Language (WQL) query as an array of instances.
  • The first_of method will return the first of all instances of a given class in the namespace.
  • Each instance is represented by a Ruby Hash for which each property value of the instance is indexed by the string name of the property as documented in the WMI Schema or as registered in the local system's WMI repository.
  • The string name specified to the aformentioned Hash is case insensitive.


Use of the instances_of, query, and first_of methods of the WmiLite::Wmi object is demonstrated below.

Count cores in the system
cores = 0
wmi = WmiLite::Wmi.new
processors = wmi.instances_of('Win32_Processor')
processors.each do | processor |
  cores += processor['numberofcores']
puts "\nThis system has #{cores} core(s).\n"
Determine if the system is domain-joined
wmi = WmiLite::Wmi.new
computer_system = wmi.first_of('Win32_ComputerSystem')
is_in_domain = computer_system['partofdomain']
puts "\nThis system is #{is_in_domain ? '' : 'not '}domain joined.\n"
List Group Policy Objects (GPOs) applied to the system
wmi = WmiLite::Wmi.new('root\rsop\computer')
gpos = wmi.instances_of('RSOP_GPO')
puts "\n#{'GPO Id'.ljust(40)}\tName"
puts "#{'------'.ljust(40)}\t----\n"
gpos.each do | gpo |
  gpo_id = gpo['guidname']
  gpo_display_name = gpo['name']
  puts "#{gpo_id.ljust(40)}\t#{gpo_display_name}"
puts 'No GPOs' if gpos.count == 0
puts "Ruby processes:\n"
wmi = WmiLite::Wmi.new
processes = wmi.query('select * from Win32_Process where Name LIKE \'%ruby%\'')
puts "\n#{'Process Id'.ljust(10)} Name"
puts "#{'----------'.ljust(10)} ----\n"
processes.each do | process |
  pid = process['processid']
  name = process['name']
  puts "#{pid.to_s.ljust(10)} #{name}"

License & Authors

Author:: Adam Edwards ([email protected]) Copyright:: Copyright (c) 2014 Chef Software, Inc. License:: Apache License, Version 2.0

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at


Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.