PowerShell Cmdlets

Windows PowerShell commands or Cmdlets (pronounced as command-lets) are the commands which can be executed through PowerShell (PS). At first glance, they look quite similar to the traditional DOS commands but they are quite different from the traditional concept of commands, in which people usually think of compiled console-based executable applications. Instead, these commands are built on top of the .NET Framework and are .NET classes usable only within the context of Windows PowerShell.

In other words, Cmdlets are really .NET classes compiled into Dynamic Link Libraries (DLLs) that are loaded by Windows PowerShell. They use the same memory space as the PowerShell process, which is one reason why they are more efficient than console applications. Don’t believe me? Wait, I will give you a proof.

To ensure that command names are intuitive and descriptive, all Cmdlets are given names in the verb–noun format, in which the verb describes what the Cmdlet does and the noun describes what it acts on. Here are some examples of Cmdlets:

·         Get-Service

·         Set-Date

·         Remove-Item

·         Write-Host

 You can find well over 200 Cmdlets defined within Windows PowerShell out of the box. Although the available Cmdlets give you plenty of flexibility in and of themselves, you can install additional Cmdlets from Microsoft (and even from other vendors) to provide more application-specific functionality. Microsoft Exchange 2007, for example, comes with the Exchange Management Shell, which is a set of Cmdlets built on top of Windows PowerShell to provide enhanced Microsoft Exchange management capabilities.

You can find all the Cmdlets by running Get-Command on PS prompt. So let’s try out the classic ‘Hello World’ on PS console. Launch PS from All Programs -> Accessories -> Windows PowerShell (if you have Win7/WS08 R2, otherwise you need to install it separately). Once PS screen launched and prompt is ready, type

 Write-Host “Hello World”

And press enter. It will execute the Cmdlet and show the output. You can try out few more cmdlets, such as Read-Host (yes! You got it correct; it’s for taking input from user). One of the striking features of PS is its excellent help content, which can be accessed through Cmdlet: Get-Help. If you want to see help content for a specific Cmdlet, type

 Get-Help [Cmdlet]

I promised you to give you a proof that Cmdlets are based on .NET framework. Let’s try out Read-Host Cmdlet as below.

 $c = Read-Host “What’s your Rashee?”

In PowerShell, you can define a variable by putting $ sign in the beginning of its name. Type the above line on PS Console and Hit Enter. It will prompt the user like below:

What’s Your Rashee?:

Type some word (or even your Zodiac) and press enter. The value is stored in $c variable. If you type $c on prompt and hit enter, you can verify it. Now type $c and a dot “.” without any space ($c.), and start pressing Tab key. You will see all the methods which a .NET object supports such as ToString(). The Tab key is like the IntelliSense of Visual Studio. Try out working with some methods.

 In the next article, we will explore another surprising feature of PS, Pipelines