Capture program stdout and stderr to separate variables

One option is to combine the output of stdout and stderr into a single stream, then filter.

Data from stdout will be strings, while stderr produces System.Management.Automation.ErrorRecord objects.

$allOutput = & myprogram.exe 2>&1$stderr = $allOutput | ?{ $_ -is [System.Management.Automation.ErrorRecord] }$stdout = $allOutput | ?{ $_ -isnot [System.Management.Automation.ErrorRecord] }

The easiest way to do this is to use a file for the stderr output, e.g.:

$output = & myprogram.exe 'argv[0]', 'argv[1]' 2>stderr.txt$err = get-content stderr.txtif ($LastExitCode -ne 0) { ... handle error ... }

I would also use $LastExitCode to check for errors from native console EXE files.

You should be using Start-Process with -RedirectStandardError -RedirectStandardOutput options. This other post has a great example of how to do this (sampled from that post below):

$pinfo = New-Object System.Diagnostics.ProcessStartInfo$pinfo.FileName = "ping.exe"$pinfo.RedirectStandardError = $true$pinfo.RedirectStandardOutput = $true$pinfo.UseShellExecute = $false$pinfo.Arguments = "localhost"$p = New-Object System.Diagnostics.Process$p.StartInfo = $pinfo$p.Start() | Out-Null$p.WaitForExit()$stdout = $p.StandardOutput.ReadToEnd()$stderr = $p.StandardError.ReadToEnd()Write-Host "stdout: $stdout"Write-Host "stderr: $stderr"Write-Host "exit code: " + $p.ExitCode