powershell - Obtaining ExitCode using Start-Process and WaitForExit instead of -Wait

Question

I'm trying to run a program from PowerShell, wait for the exit, then get access to the ExitCode, but I am not having much luck. I don't want to use -Wait with Start-Process, as I need some processing to carry on in the background.

Here's a simplified test script:

cd "C:Windows"

# ExitCode is available when using -Wait...
Write-Host "Starting Notepad with -Wait - return code will be available"
$process = (Start-Process -FilePath "notepad.exe" -PassThru -Wait)
Write-Host "Process finished with return code: " $process.ExitCode

# ExitCode is not available when waiting separately
Write-Host "Starting Notepad without -Wait - return code will NOT be available"
$process = (Start-Process -FilePath "notepad.exe" -PassThru)
$process.WaitForExit()
Write-Host "Process exit code should be here: " $process.ExitCode

Running this script will cause Notepad to be started. After this is closed manually, the exit code will be printed, and it will start again, without using -wait. No ExitCode is provided when this is quit:

Starting Notepad with -Wait - return code will be available
Process finished with return code:  0
Starting Notepad without -Wait - return code will NOT be available
Process exit code should be here:

I need to be able to perform additional processing between starting the program and waiting for it to quit, so I can't make use of -Wait. How can I do this and still have access to the .ExitCode property from this process?

Answer 1

There are two things to remember here. One is to add the -PassThru argument and two is to add the -Wait argument. You need to add the wait argument because of this defect.

-PassThru [<SwitchParameter>]
    Returns a process object for each process that the cmdlet started. By default,
    this cmdlet does not generate any output.

Once you do this a process object is passed back and you can look at the ExitCode property of that object. Here is an example:

$process = start-process ping.exe -windowstyle Hidden -ArgumentList "-n 1 -w 127.0.0.1" -PassThru -Wait
$process.ExitCode

# This will print 1

If you run it without -PassThru or -Wait, it will print out nothing.

The same answer is here: How do I run a Windows installer and get a succeed/fail value in PowerShell?

It's also worth noting that there's a workaround mentioned in the "defect report" link above, which is as following:

# Start the process with the -PassThru command to be able to access it later
$process = Start-Process 'ping.exe' -WindowStyle Hidden -ArgumentList '-n 1 -w 127.0.0.1' -PassThru

# This will print out False/True depending on if the process has ended yet or not
# Needs to be called for the command below to work correctly
$process.HasExited

# This will print out the actual exit code of the process
$process.GetType().GetField('exitCode', 'NonPublic, Instance').GetValue($process)