Problem
You want to work with data and functionality provided by the WMI facilities in Windows.
Solution
To retrieve all instances of a WMI class, use the GetWmiObject cmdlet:
GetWmiObject ComputerName Computer Class Win32_Bios To retrieve specific instances of a WMI class, using a WMI filter, supply an argument to the –Filter parameter of the GetWmiObject cmdlet:
GetWmiObject Win32_Service Filter "StartMode = 'Auto'"
To retrieve instances of a WMI class using WMI’s WQL language, use the [WmiSearcher] type shortcut:
$query = [WmiSearcher] "SELECT * FROM Win32_Service WHERE StartMode = 'Auto'"
$query.Get() To retrieve a specific instance of a WMI class using a WMI filter, use the [Wmi] type shortcut:
[Wmi] 'Win32_Service.Name="winmgmt"'
To retrieve a property of a WMI instance, access that property as you would access a .NET property:
$service = [Wmi] 'Win32_Service.Name="winmgmt"' $service.StartMode
To invoke a method on a WMI instance, invoke that method as you would invoke a .NET method:
$service = [Wmi] 'Win32_Service.Name="winmgmt"' $service.ChangeStartMode("Manual") $service.ChangeStartMode("Automatic")
To invoke a method on a WMI class, use the [WmiClass] type shortcut to access that WMI class. Then, invoke that method as you would invoke a .NET method:
$class = [WmiClass] "Win32_Process" $class.Create("Notepad")
Discussion
Working with WMI has long been a staple of managing Windows systems—especially systems that are part of corporate domains or enterprises. WMI supports a huge amount of Windows management tasks, albeit not in a very userfriendly way.
Traditionally, administrators required either VBScript or the WMIC commandline tool to access and manage these systems through WMI. While powerful and useful, these techniques still provided plenty of opportunities for improvement. VBScript lacks support for an ad hoc investigative approach, and WMIC fails to provide (or take advantage of) knowledge that applies to anything outside WMIC.
In comparison, PowerShell lets you work with WMI just like you work with the rest of the shell. WMI instances provide methods and properties, and you work with them the same way you work with methods and properties of other objects in PowerShell.
Not only does PowerShell make working with WMI instances and classes easy once you have them, but it also provides a clean way to access them in the first place. For most tasks, you need only to use the simple [Wmi], [WmiClass],or [WmiSearcher] syntax as shown in the solution.
Along with WMI’s huge scope, though, comes a related problem: finding the WMI class that accomplishes your task.
Some advanced WMI tasks require that you enable your security privileges or adjust the packet privacy settings used in your request. The syntax given by the solution does not directly support these tasks, but PowerShell still supports these options by providing access to the underlying objects that represent your WMI query.
When you want to access a specific WMI instance with the [Wmi] accelerator, you might at first struggle to determine what properties WMI lets you search on. These properties are called key properties on the class.
For more information about the GetWmiObject cmdlet, type GetHelp GetWmiObject.
