Snap-Ins

A snap-in is essentially a collection of cmdlets. For example, running the Get-Pssnapin cmdlet shows the snap-ins provided with the basic shell as shown below:

 PS C:\> get-pssnapin Name        : Microsoft.PowerShell.Core PSVersion   : 1.0 Description : This Windows PowerShell snap-in contains Windows PowerShell management ... Name        : Microsoft.PowerShell.Host PSVersion   : 1.0 Description : This Windows PowerShell snap-in contains cmdlets used by the Windows Po... Name        : Microsoft.PowerShell.Management PSVersion   : 1.0 Description : This Windows PowerShell snap-in contains management cmdlets used to man... Name        : Microsoft.PowerShell.Security PSVersion   : 1.0 Description : This Windows PowerShell snap-in contains cmdlets to manage Windows Powe... Name        : Microsoft.PowerShell.Utility PSVersion   : 1.0 Description : This Windows PowerShell snap-in contains utility Cmdlets used to manipu... 

You can add the -pssnapin parameter to the Get-Command cmdlet to see which cmdlets are in a particular snap-in. Below is a partial list for the Microsoft.PowerShell.Utility snap-in:

 PS C:\> get-command -pssnapin microsoft.powershell.utility CommandType     Name                         Definition -----------     ----                         ---------- Cmdlet          Add-Member                   Add-Member [-M Cmdlet          Clear-Variable               Clear-Variable Cmdlet          Compare-Object               Compare-Object Cmdlet          ConvertTo-Html               ConvertTo-Html Cmdlet          Export-Alias                 Export-Alias [ Cmdlet          Export-Clixml                Export-Clixml Cmdlet          Export-Csv                   Export-Csv [-P Cmdlet          Format-Custom                Format-Custom Cmdlet          Format-List                  Format-List [[ Cmdlet          Format-Table                 Format-Table [ Cmdlet          Format-Wide                  Format-Wide [[ Cmdlet          Get-Alias                    Get-Alias [[-N Cmdlet          Get-Culture                  Get-Culture [- Cmdlet          Get-Date                     Get-Date [[-Da Cmdlet          Get-Host                     Get-Host [-Ver Cmdlet          Get-Member                   Get-Member [[- Cmdlet          Get-TraceSource              Get-TraceSourc 

As you'll learn later in this chapter, you can make custom versions of PowerShell that include just the snap-ins you want, which essentially creates task-specific versions of the shell.

But wait a moment. What will happen if you create a script that relies on a particular snap-in being present, and share that script with an administrator who doesn't have that snap-in? The answer is that the script won't work. One way you can help remember which snap-ins a script requires, is to use a self-documenting feature in PowerShell. For example, you can add something like the following to your script:

 #requires -PSSnapIn Microsoft.PowerShell.Utility 

Of course, you don't need to specify this for the core snap-ins because they're always present, so there's no way to create a shell without them. However, if you're using nonstandard snap-ins, it's a good idea to add #requires to your script.