retrieve vhdx path from a remote server - powershell

Question

hi i' m trying to retrieve the vhdx of specified vmname from the remote host server
here part of the script
$pth="C:\path\resize-vm"
$list=gc $pth\list-host.txt
foreach ($hostserver in $list) {
$vm=(Invoke-Command -ComputerName $hostserver -ScriptBlock {Get-VM}).VMName
Write-Host -NoNewline " here the vm installed in " $hostserver `r`n $vm
$vmname=Read-Host -Prompt "please chose a vmname to resize "
#the issue in the last line
$pathvhd=Invoke-Command -ComputerName $hostserver -ScriptBlock {(Get-VMHardDiskDrive -VMName $vmname).path}
When I launch this command $vmname="dc-kozhan"
I am getting this error
Cannot validate argument on parameter 'VMName'. The argument is null
or empty. Provide an argument that is not null or empty, and then try
the command again.
+ CategoryInfo : InvalidData: (:) [Get-VMHardDiskDrive], ParameterBindingValidationException
+ FullyQualifiedErrorId : ParameterArgumentValidationError,Microsoft.HyperV.PowerShell.Commands.GetVMHardDiskDrive
Command
+ PSComputerName : h-uludag-3
But when I specified dc-kozhan literally it work
PS C:\Users> Invoke-Command -ComputerName $hostserver -ScriptBlock {(Get-VMHardDiskDrive -VMName "DC-KOZAHAN")
.path}
V:\DC-KOZAHAN\DC-KOZAHAN-SYSTEM.vhdx
V:\DC-KOZAHAN\DC-KOZAHAN-DIRECTORY.vhdx
V:\DC-KOZAHAN\DC-KOZAHAN-SYSVOL.vhdx
V:\DC-KOZAHAN\DC-KOZAHAN-BACKUP.vhdx
does anyone have an idea why it does not work when it's specified in a variable

Answer 1

You need to understand how to pass arguments inside the scriptblock. The scope is different when you try to pass the value inside the scriptblock. As a result, $VMname is becoming null in your first statement.
Kindly change your existing Invoke-command statement to the below one:
Invoke-Command -ComputerName $hostserver -ScriptBlock {Param([string]$vmname)(Get-VMHardDiskDrive -VMName $vmname)} -ArgumentList $vmname
Also, my suggestion for you to read about the argumentlist in powershell in case invoke-command
Hope it helps.