Asynchronously Logging Stdout from a PowerShell Process - powershell

Question

I need to start a long-running process in a PowerShell script and capture the StandardOutput to a file as it is being generated. I'm currently using an asynchronous approach and appending the output to a text file each time an OutputDataReceived event is fired. The following code excerpt illustrates:
$PSI = New-Object System.Diagnostics.ProcessStartInfo
$PSI.CreateNoWindow = $true
$PSI.RedirectStandardOutput = $true
$PSI.RedirectStandardError = $true
$PSI.UseShellExecute = $false
$PSI.FileName = $EXECUTE
$PSI.RedirectStandardInput = $true
$PSI.WorkingDirectory = $PWD
$PSI.EnvironmentVariables["TMP"] = $TMPDIR
$PSI.EnvironmentVariables["TEMP"] = $TMPDIR
$PSI.EnvironmentVariables["TMPDIR"] = $TMPDIR
$PROCESS = New-Object System.Diagnostics.Process
$PROCESS.StartInfo = $PSI
[void]$PROCESS.Start()
# asynchronously listen for OutputDataReceived events on the process
$sb = [scriptblock]::Create("`$text = `$Event.SourceEventArgs.Data; `$OUTFIL = `$Event.MessageData; Add-Content $OUTFIL.out `$text")
$EVENT_OBJ = Register-ObjectEvent -InputObject $PROCESS -EventName OutputDataReceived -Action $sb -MessageData "$OUTFIL.out"
# asynchronously listen for ErrorDataReceived events on the process
$sb2 = [scriptblock]::Create("`$text = `$Event.SourceEventArgs.Data; Write-Host `$text;")
$EVENT_OBJ2 = Register-ObjectEvent -InputObject $PROCESS -EventName ErrorDataReceived -Action $sb2
# begin asynchronous read operations on the redirected StandardOutput
$PROCESS.BeginOutputReadLine();
# begin asynchronous read operations on the redirected StandardError
$PROCESS.BeginErrorReadLine();
# write the input file contents to standard input
$WRITER = $PROCESS.StandardInput
$READER = [System.IO.File]::OpenText("$IN_FILE")
try
{
while (($line = $READER.ReadLine()) -ne $null)
{
$WRITER.WriteLine($line)
}
}
finally
{
$WRITER.close()
$READER.close()
}
$Process.WaitForExit() | Out-Null
# end asynchronous read operations on the redirected StandardOutput
$PROCESS.CancelOutputRead();
# end asynchronous read operations on the redirected StandardError
$PROCESS.CancelErrorRead();
Unregister-Event -SubscriptionId $EVENT_OBJ.Id
Unregister-Event -SubscriptionId $EVENT_OBJ2.Id
The issue with this approach is the large amount of output being generated and the latency caused by having to open and close the text file each event (i.e., Add-Content $OUTFIL.out $text) is called each time the event is fired).
$sb = [scriptblock]::Create("`$text = `$Event.SourceEventArgs.Data; `$OUTFIL = `$Event.MessageData; Add-Content $OUTFIL.out `$text")
In each case the actual process will complete minutes before all of the output data has been written to the text file.
Is there a better approach to doing this? A faster way to append text to the file?