Trouble backgrounding .bat file invocations

BillJr58 — Fri, 13 Apr 2012 05:00:00 GMT

Background:
I'm using PowerShell to automate a legacy build process. There are a couple .bat files I need to invoke and would like to run them in parallel. They end with a "Pause" command, so I need to supply input in order for the jobs to complete.

I can invoke the .bat files serially, simply using " " | to satisfy the Pause command. The trouble began when I tried to use Start-Job to run them in parallel. Can you explain why PowerShell is not happy with this code?

Code snippet:

   $jobs = @()
   foreach ( $jn in "compile_all_ada", "compile_all_c" ) {
      $bf = (Get-Location),"$jn.bat" -join "\"
      $jobs += Start-Job {
         (" " | & $bf) | Out-File -FilePath $jn.log -Encoding ascii -Force
         } -Name $jn
   }

Invocation error:

>>> $jobs | Receive-Job
The expression after '&' in a pipeline element produced an invalid object. It must result in a command name, script block
or CommandInfo object.
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : BadExpression

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Trouble backgrounding .bat file invocations