How to save output from Foreach parallel loop in PowerShell?

In PowerShell 7, saving the output of the foreach parallel loop requires some tricks. It is unlike a simple foreach loop. For example, in a simple foreach loop, we can directly store output to a variable that is declared outside as shown below.

$output = @()

foreach ($service in (Get-Service | where{$_.StartType -eq 'Disabled'})){
    $output += [PSCustomObject]@{
        'Name' = $service.name
        'StartType' = $service.StartType
        'Status' = $service.Status
    }
}

$output

Let’s try the same with PowerShell 7.

$output = @()

Get-Service | where{$_.StartType -eq 'Disabled'} | foreach-object -Parallel {
  $out= $using:output
  $service = $_
  
  $out+= [PSCustomObject]@{
        'Name' = $service.name
        'StartType' = $service.StartType
        'Status' = $service.Status
  }
}

$output

There will be no output because $out variable scope outside the foreach parallel loop is unknown. Instead, we can directly store the value to the variable outside the foreach parallel loop.

$output = @()

$output += Get-Service | where{$_.StartType -eq 'Disabled'} | foreach-object -Parallel {
  $service = $_
  [PSCustomObject]@{
        'Name' = $service.name
        'StartType' = $service.StartType
        'Status' = $service.Status
  }
}

$output

The output will be the same as the previous output.