Run a process analyzing output for errors

RunCommand.ps1

# see https://stackoverflow.com/questions/23239127/powershell-stream-process-output-and-errors-while-running-external-process/28440479
function RunCommand
{
    [CmdletBinding()]
    param (
        [Parameter(Mandatory=$True)]
        [string]   $FileName,
        [Parameter(Mandatory=$True)]
        [string[]] $Arguments,
        [string]   $OutputPrefix = "> ",
        [string]   $ErrorCountPattern = $null
    )

    # see https://social.technet.microsoft.com/Forums/office/en-US/07bbb0e5-0d31-451c-97e8-fad42361389f/passing-variable-to-registerobjectevent-action-block?forum=ITCG
    $eventData = New-Object PSObject -Property @{
        # in
        OutPrefix = $OutputPrefix
        ErrorCountPattern = $ErrorCountPattern
        # out
        ErrCount = [int]0
    }

    # Setup stdin\stdout redirection
    $StartInfo = New-Object System.Diagnostics.ProcessStartInfo -Property @{
                    FileName = $FileName
                    Arguments = $arguments
                    UseShellExecute = $false
                    RedirectStandardOutput = $true
                    RedirectStandardError = $true
                    CreateNoWindow = $true
                }

    # Create new process
    $Process = New-Object System.Diagnostics.Process

    # Assign previously created StartInfo properties
    $Process.StartInfo = $StartInfo

    # Register Object Events for stdin\stdout reading
    $OutEvent = Register-ObjectEvent -InputObject $Process -EventName OutputDataReceived -Action {
        $prefix = $Event.MessageData.OutPrefix
        $line = $Event.SourceEventArgs.Data
        Write-Host "${prefix}${line}"
    } -MessageData $eventData
    $ErrEvent = Register-ObjectEvent -InputObject $Process -EventName ErrorDataReceived -Action {
        $prefix = $Event.MessageData.OutPrefix
        $line = $Event.SourceEventArgs.Data
        Write-Host "${prefix}${line}"
        if ($line -match $Event.MessageData.ErrorCountPattern) {
            $Event.MessageData.ErrCount = $Matches[1]
        }
    } -MessageData $eventData

    # Start process
    [void]$Process.Start()

    # Begin reading stdin\stdout
    $Process.BeginOutputReadLine()
    $Process.BeginErrorReadLine()

    # Do something else while events are firing
    do
    {
        # Write-Host 'Still alive!' -ForegroundColor Green
        Start-Sleep -Seconds 1
    }
    while (!$Process.HasExited)

    # Unregister events
    $OutEvent.Name, $ErrEvent.Name |
        ForEach-Object { Unregister-Event -SourceIdentifier $_ }

    $ExitCode = $Process.ExitCode

    $Process.Dispose()

    return @{
        ExitCode = $ExitCode
        Errors = $eventData.ErrCount
    }
}





$res = RunCommand -OutputPrefix 'MSDEPLOY> ' -ErrorCountPattern '^Error count:\s+(\d+)' -FileName 'C:\Program Files\IIS\Microsoft Web Deploy V3\MSDeploy.exe' -Arguments @(
    "-verb:sync",
    "-source:contentPath=c:\temp\test3",
    "-dest:contentPath=c:\temp\test2"
    #,"-whatif"
)


Write-Host "RC> $( $res.ExitCode )" -ForegroundColor Cyan
Write-Host "ERRCOUNT> $( $res.Errors )" -ForegroundColor Cyan