Powershell's Invoke-Command won't take in a variable for -ComputerName parameter?

Question

I'm pulling my hair out here, because I just can't seem to get this to work, and I can't figure out how to google this issue. I'm running Powershell 2.0. Here's my script:

$computer_names = "server1,server2"
Write-Output "Invoke-Command -ComputerName $computer_names -ScriptBlock { 
    Get-WmiObject -Class Win32_LogicalDisk | 
    sort deviceid | 
    Format-Table -AutoSize deviceid, freespace 
}"
Invoke-Command -ComputerName $computer_names -ScriptBlock { 
    Get-WmiObject -Class Win32_LogicalDisk | 
    sort deviceid | 
    Format-Table -AutoSize deviceid, freespace 
}

The last command gives the error:

Invoke-Command : One or more computer names is not valid. If you are trying to 
pass a Uri, use the -ConnectionUri parameter or pass Uri objects instead of 
strings.

But when I copy the output of the Write-Output command to the shell and run that, it works just fine. How can I cast the string variable to something that Invoke-Command will accept? Thanks in advance!

Answer 1

Jamey and user983965 are correct, in that your declaration is wrong. However foreach here is not mandatory. If you just fix your array declaration like this, it will work:

$computer_names = "server1","server2"
Invoke-Command -ComputerName $computer_names -ScriptBlock { 
    Get-WmiObject -Class Win32_LogicalDisk | 
    sort deviceid | 
    Format-Table -AutoSize deviceid, freespace 
}