PowerShell Remoting $Using variable scope

Question

I have folder c:\test where I have three files: “file1”, “file2”, “file3”

Following script:

$remoteSession = New-PSSession -ComputerName localhost
$folder = "c:\test"
$exclude =@("c:\test\file1","c:\test\file2")

Invoke-Command -Session $remoteSession -ScriptBlock {    
    #$Using:exclude
    Get-ChildItem -Path $Using:folder -recurse | Where {$Using:exclude -notcontains $_.FullName}
}

Remove-PSSession $remoteSession

Gives the result:

However, if I uncomment “$Using:exclude” I get the result:

Suddenly exclude list starts working properly

I get: New-PSSession : [localhost] Beim Verbinden mit dem Remoteserver "localhost" ist folgender Fehler aufgetreten: Zugriff verweigert — Timo
– Timo, Commented May 14, 2020 at 5:17
ok, I have to be Administrator to start a pssession. Another issue: where do you uncomment, it is already uncommented. — Timo
– Timo, Commented May 14, 2020 at 5:28

Community · Accepted Answer · 2014-11-24 09:42:07Z

21

Just specifying $Using:exclude in the Where-Object cmdlet doesn't work because it is in a nested scriptblock.

In your case , the Using:folder works because it is a local variable directly passed to the Invoke-Command scriptblock.

But "Using:exclude is passed to a scriptblock for Where-Object, which is itself nested inside the scriptblock for Invoke-Command.

$Using allows to pass local variables to scriptblocks only one level deep, not to scriptblocks nested any further. This behaviour is not specific to the Where-Object scriptblock, any cmdlet which has a parameter taking a scriptblock behaves like this when it is inside a Invoke-Command scriptblock.

Unfortunately, I don't think this behaviour is documented.

By uncommenting $Using:exclude at the beginning of the Invoke-Command scriptblock, you are effectively declaring the variable $exclude inside the remote session. So, in this case, $exclude becomes a local variable inside the Invoke-Command scriptblock and can be passed one level further, to the nested Where-Object scriptblock.

That's why it works when you uncomment $Using:exclude at the beginning of the Invoke-Command scriptblock, it's a workaround for the behaviour of $Using.

For the official help information about this run :

Get-Help about_remote_variables -Full

edited Nov 24, 2014 at 9:42

CommunityBot

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answered Aug 9, 2014 at 12:45

Mathieu Buisson

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3 Comments

user3884425 Over a year ago

see my answer to this post :)

Mike Shepard Over a year ago

In your answer you "$using:" the two variables in the outermost scope of the remoted scriptblock, which allows them to be passed into the & scriptblocks. @Mathieu explained this well, I think.

Timo Over a year ago

In my case I get all three files when uncommenting $Using:exclude

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