Powershell Invoke-Command passing environment variables - powershell

Question

I wish to use Invoke-Command passing environment variables from the calling machine to the server where Invoke-Command is being executed.
I want this to work:
Invoke-Command -ComputerName MyServer-ScriptBlock {
$env:VAR=$using:env:USERNAME
Write-Host $env:VAR
}
But the output for this command is empty. If I do not use the $using scope modifier, and just assign the variable directly I get the expected output ("VAR").
Invoke-Command -ComputerName MyServer -ScriptBlock {
$env:VAR="VAR"
Write-Host $env:VAR
}
So, can I use $using with environment variables? If not, is there an easy way to pass environment variables over to the remote computer where Invoke-Command is running?

Answer 1

One option would be to assign the environment variable to a standard variable before invoking:
$username = $env:USERNAME
Invoke-Command -ComputerName MyServer-ScriptBlock {
$env:VAR=$using:userName
Write-Host $env:VAR
}
Note that assigning environment variables like this ($env:VAR=<value>) won't persist once your session ends. Use the Environment.SetEnvironmentVariable() method to do that.

Answer 2

I think you could use -ArgumentList. See https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/invoke-command?view=powershell-6
Invoke-Command -ComputerName MyServer -ArgumentList $env:USERNAME -ScriptBlock {
Param ($x)
Write-Host $x
}

Answer 3

Update: The bug described below has been fixed in v7.3.
The existing answers show helpful workarounds.
It looks like you've hit a bug, present up to PowerShell 7.2.x:
The $using: scope - which is required for accessing variable values from the caller's scope in all out-of-runspace executions (see this answer) - should also support namespace variable notation (see this answer).
Thus, you should be able to pass a namespace-notation variable reference such as $env:USERNAME as $using:env:USERNAME:
indeed you can in the context of jobs (child-process-based background jobs started with Start-Job and thread-based jobs started with Start-ThreadJob); e.g.:
$env:FOO = 'bar'
# Outputs 'bar', as expected.
Start-Job { $using:env:FOO } | Receive-Job -Wait -AutoRemoveJob
but, as of PowerShell 7.1, that doesn't work with PowerShell remoting, such as Invoke-Command -ComputerName, as in your case.
The potential bug has been reported in GitHub issue #16019.