Why is the PowerShell SetEnvironmentVariable command deleting the existing variable?

Question

Good-day all,

I've written a PowerShell function to help me update a System Environment Variable on a bunch of Windows 7 and 10 Enterprise machines. I've noticed, however, that my "[System.Environment]::SetEnvironmentVariable()" command is deleting the existing variable and not changing its value - like I'm expecting it to.

What am I doing wrong?

Here's a snippet of the relevant code:

$ComputerName = "SERVER1"
$MyEnvVar = "C:\Some_Path\"

ForEach ($Computer in $ComputerName){

    $Online = Test-Connection -ComputerName $Computer -Count 2 -Quiet

    If ($Online -eq $True){
        $OldValue = Invoke-Command $Computer -ScriptBlock {[System.Environment]::GetEnvironmentVariable("MyVariableName","Machine")}
        Write-Host "Old Value is: $OldValue"
        Invoke-Command $Computer -ScriptBlock {[System.Environment]::SetEnvironmentVariable("MyVariable","$MyEnvVar","Machine")}
        $NewValue = Invoke-Command $Computer -ScriptBlock {[System.Environment]::GetEnvironmentVariable("MyVariableName","Machine")}
        Write-Host "New Value is: $NewValue"

    }
}

$MyEnvVar is evaluated in the context of the remote machine rather than your local value. Use $using:MyEnvVar to remote it. — Jeroen Mostert
– Jeroen Mostert, Commented May 15, 2019 at 14:45
Do I do that when I'm declaring $MyEnvVar or when I'm using it in the Set command? — Kismet Agbasi
– Kismet Agbasi, Commented May 15, 2019 at 14:57

Community · Accepted Answer · 2020-06-20 09:12:55Z

2

Change this line:

  Invoke-Command $Computer -ScriptBlock {[System.Environment]::SetEnvironmentVariable("MyVariable","$MyEnvVar","Machine")}

to:

 Invoke-Command $Computer -ScriptBlock {[System.Environment]::SetEnvironmentVariable("MyVariable",$Using:MyEnvVar,"Machine")}

From about_scopes:

Example 5: Using a Local Variable in a Remote Command

For variables in a remote command created in the local session, use the Using scope modifier. PowerShell assumes that the variables in remote commands were created in the remote session.

Also checkout about_remote_variable.

edited Jun 20, 2020 at 9:12

CommunityBot

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answered May 15, 2019 at 17:23

Moerwald

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1 Comment

Kismet Agbasi Over a year ago

That worked like a charm and I've learned something new in the process, thank you.

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