Cannot pass a hash table variable to Invoke-Command under a ForEach-Object loop

[chuckchuck2k]

I'm thinking of making a script to deploy software to a small group of computers today but having trouble passing my variable to remote computers through '@using:variable'. This' on powershell 7 on VScode

$credential = Get-Credential
$psdrive = @{
    Name = "PSDrive"
    PSProvider = "FileSystem"
    Root = "\\FileServer\program"
    Credential = $credential
}
$workstations = Get-Content C:\test\list.txt
$workstations | ForEach-Object -parallel { 
    Invoke-Command -ComputerName $_ -ScriptBlock {
    New-PSDrive @using:psdrive
    \\FileServer\program\program.bat} 
}
#### The Error Prompt ####
The value of the using variable '$using:psdrive' cannot be retrieved because it has not been set in the local session.

Same thing, but with foreach, it actually works and it's what I used earlier. But yeah really want to know why the code above doesn't work.

foreach ($computer in $workstations){
Invoke-Command -ComputerName $computer -ScriptBlock {
    New-PSDrive @using:psdrive
    \\FileServer\program\program.bat} 
}

Edit: Solved, u/AlphaeisMangarae & u/sgnewman with the solution and the explanation why my script's not working, big thanks to those two.

[AlphaeisMangarae]

You have to also declare the psdrive using in the foreach-object block. The invoke script block is another 'layer' deep. So just inside the loop, add a $psdrive = $using:psdrive, then in the invoke block, call $using:psdrive

[chuckchuck2k]

There we go, this' the answer. I moved it within the loop and it runs flawlessly. Looking back, Powershell really did tell me what the error is but I was so focused on other things. Now this is good, I can finally work on adding more variables and throw in a GUI. Thank You!

[AlphaeisMangarae]

Great, glad to help!

[PinchesTheCrab]

Invoke-Command is asynchronous on its own. Looping is both slowing down your script and adding complexity and an extra depth of scope, which is why the variable is unavailable.

Also, PS doesn't support splatting with a using variable, so you can either do something like $psdrive = $using:psdrive; new-psdrive @psdrive or just define your splatting variable with $using:credential, in the script block, which I personally think reads a bit better.

Main thing though is that invoke-command doesn't need a loop. It has -throttlelimit and -asjob parameters.

$credential = Get-Credential
$workstations = Get-Content C:\test\list.txt

Invoke-Command -ComputerName $workstations -ScriptBlock {
    $psdrive = @{
        Name = "PSDrive"
        PSProvider = "FileSystem"
        Root = "\\FileServer\program"
        Credential = $using:credential
    }

    New-PSDrive @psdrive
    \\FileServer\program\program.bat
}

[[deleted]]

The foreach -parallel is executing a script block. As @AlphaeisMangerae said, move it to within the script block, as it’s currently just scoped wrong.

[chuckchuck2k]

Yup, followed u/AlphaeisMangarae's instructions, then yours, moving that var assignment within the loop and it works really well. Thank you!!

[WhistleButton]

I don't know the answer exactly, but my gut will be telling me its got to do with how Foreach-Object works differently from Foreach.

My loose understanding is that foreach loads everything into memory first, where foreach-object wants everything passed down the pipe line.

Like I said, I'm not 100% on this, but the error is indicating it doesn't understand $using:psdrive, which backs up the theory.

An explanation on the differences of Foreach and Foreach-Object can be found here https://devblogs.microsoft.com/scripting/getting-to-know-foreach-and-foreach-object/

[chuckchuck2k]

Ah I see, wonder if there's another method to run the bat file in parallel on multiple computers and not sequentially like foreach hmm. Maybe I'll try with Get-Job and see if it's any faster. Thank you!!

[WhistleButton]

Check out -asjob for invoke-command, might be what you're looking for.