Powershell – How to check if PowerShell snap-in is already loaded before calling Add-PSSnapin

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I have a group of PowerShell scripts that sometimes get run together, sometimes one at a time. Each of the scripts requires that a certain snap-in be loaded.

Right now each script is calling Add-PSSnapin XYZ at the beginning.

Now if I run multiple scripts back-to-back the subsequent scripts throw:

Cannot add Windows PowerShell snap-in XYZ because it is alerady added. Verify the name of the snap-in and try again.

How can I have each script check to see if the snap-in is already loaded before calling Add-PSSnapin?

Best Answer

You should be able to do it with something like this, where you query for the Snapin but tell PowerShell not to error out if it cannot find it:

if ( (Get-PSSnapin -Name MySnapin -ErrorAction SilentlyContinue) -eq $null )
{
    Add-PsSnapin MySnapin
}

Related Solutions

PowerShell says “execution of scripts is disabled on this system.”

If you're using Windows Server 2008 R2 then there is an x64 and x86 version of PowerShell both of which have to have their execution policies set. Did you set the execution policy on both hosts?

As an Administrator, you can set the execution policy by typing this into your PowerShell window:

Set-ExecutionPolicy RemoteSigned

For more information, see Using the Set-ExecutionPolicy Cmdlet.

When you are done, you can set the policy back to its default value with:

Set-ExecutionPolicy Restricted

You may see an error:

Access to the registry key
'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PowerShell\1\ShellIds\Microsoft.PowerShell' is denied. 
To change the execution policy for the default (LocalMachine) scope, 
  start Windows PowerShell with the "Run as administrator" option. 
To change the execution policy for the current user, 
  run "Set-ExecutionPolicy -Scope CurrentUser".

So you may need to run the command like this (as seen in comments):

Set-ExecutionPolicy RemoteSigned -Scope CurrentUser

Powershell – How to verify snapin before add

You can load it if it's not loaded already:

if(-not (Get-PSSnapin VMware.VimAutomation.Core))
{
   Add-PSSnapin VMware.VimAutomation.Core
}

You could also load it anyway and ignore the error:

Add-PSSnapin VMware.VimAutomation.Core -ErrorAction SilentlyContinue

Best Answer

Related Solutions

PowerShell says “execution of scripts is disabled on this system.”

Powershell – How to verify snapin before add

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