Windows

Problem

You want to access system performance counter information from PowerShell.

Solution

To retrieve information about a specific performance counter, use the System. Diagnostics.PerformanceCounter class from the .NET Framework, as shown in Example 156.

Example 156. Accessing performance counter data through the System.Diagnostics. PeformanceCounter class

It is often helpful to perform ad hoc queries and commands against a data source such as a SQL server, Access database, or even an Excel spreadsheet. This is especially true when you want to take data from one system and put it in another, or when you want to bring the data into your PowerShell environment for detailed interactive manipulation or processing.

Problem

You want to automate a program or system task through its COM automation interface.

Solution

To instantiate and work with COM objects, use the NewObject cmdlet’s –ComObject parameter.

$shell = NewObject ComObject "Shell.Application" $shell.Windows() | FormatTable LocationName,LocationUrl

Discussion

Problem

You want to perform a WMI task in PowerShell, but can find only VBScript examples that demonstrate the solution to the problem.

Solution

To accomplish the task of a script that retrieves data from a computer, use the GetWmiObject cmdlet: foreach($printer in GetWmiObject –Computer COMPUTER Win32_Printer) { ## Work with the properties $printer.Name

Problem

You want to work with advanced features of WMI, but PowerShell’s access (through the [Wmi], [WmiClass], and [WmiSearcher] accelerators) does not directly support them.

Solution

To interact with advanced features through their .NET interface, use the PsBase property of the resulting objects.

Advanced instance features

To get WMI instances related to a given instance, call the GetRelated() method:

$instance = [Wmi] 'Win32_Service.Name="winmgmt"' $instance.PsBase.GetRelated()

Along with WMI’s huge scope comes a related problem: finding the WMI class that accomplishes your task. If you want to dig a little deeper, though, Example 152 lets you search for WMI classes by name, description, property name, or property description.

Example 152. SearchWmiNamespace.ps1

############################################################################## ## ## SearchWmiNamespace.ps1 ##

Example 152. SearchWmiNamespace.ps1 (continued)

When you want to access a specific WMI instance with PowerShell’s [Wmi] type shortcut, you might at first struggle to determine what properties WMI lets you search on. These properties are called key properties on the class. Example 151 gets all the properties you may use in a WMI filter for a given class.

Example 151. GetWmiClassKeyProperty.ps1

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'"

The PowerShell environment is phenomenally comprehensive. It provides a great surface of cmdlets to help you manage your system, a great scripting language to let you automate those tasks, and direct access to all the utilities and tools you already know.