Getting command output from Invoke-Command

Question

I'm trying to use Invoke-Command to run a command in PowerShell remotely on a number of machines, and capture their output from it, but I'm not getting any output from it. I suspect it's from how I'm using Start-Process, but I'm not sure.

$RunCommand = {
    Start-Process "$env:ProgramFiles\Some Program\someprogram.exe" -ArgumentList "-SignatureUpdate"
}

$comp_list = @(Get-Content "c:\temp\comp_list.txt")
$cred = Get-Credential

$jobs = Invoke-Command -Credential $cred -Computer $comp_list -ScriptBlock $RunCommand -AsJob

Wait-Job $jobs
$r = Receive-Job $jobs
$r | % { $_ > c:\temp\$($_.PScomputerName).output }

Is there a better way to invoke a command using environment variables like that?

This may be a typo but shouldn't it be Invoke-Command -ComputerName not just -computer — LinkBerest - SO sold our work
– LinkBerest - SO sold our work, Commented Mar 24, 2015 at 1:47
-Computer is an alias for -ComputerName, so either will work just fine. — supercheetah
– supercheetah, Commented Mar 24, 2015 at 1:53
ahh, should have figured. Have you tried using $ExecutionContext.InvokeCommand.NewScriptBlock() to create the script block. I've used this with Invoke-Ssh command — LinkBerest - SO sold our work
– LinkBerest - SO sold our work, Commented Mar 24, 2015 at 2:00

supercheetah · Accepted Answer · 2015-03-24 02:19:48Z

1

I've found that Start-Process is probably not the best way to capture the output from a binary unless the binary itself passes on .NET objects. What I did find that works better for this is the call operator:

$RunCommand = {
    $exe = "$env:ProgramFiles\Some Program\someprogram.exe"
    & $exe -SignatureUpdate
}

I was still not getting the output I was expecting. More specifically, I was only getting the last line of output from the command instead of the entire thing. Eventually it dawned on me that all the previous lines were being overwritten, and so I changed the last line to this:

$r | % { $_ >> c:\temp\$($_.PScomputerName).output }

Note: I changed > to >> for appending to the file.

answered Mar 24, 2015 at 2:19

supercheetah

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1 Comment

supercheetah Over a year ago

To note, this has the drawback that rerunning the script results in it appending to the end of that same file instead of creating a new one.

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