Bdtjtk

Is it possible to redirect stdout from an external program to a variable and stderr from external programs to another variable in one run?

For example:

$global:ERRORS = @();

$global:PROGERR = @();



function test() {

    # Can we redirect errors to $PROGERR here, leaving stdout for $OUTPUT?

    $OUTPUT = (& myprogram.exe 'argv[0]', 'argv[1]');



    if ( $OUTPUT | select-string -Pattern "foo" ) {

        # do stuff

    } else {

        $global:ERRORS += "test(): oh noes! 'foo' missing!";

    }

}



test;

if ( @($global:ERRORS).length -gt 0 ) {

    Write-Host "Script specific error occurred";

    foreach ( $err in $global:ERRORS ) {

        $host.ui.WriteErrorLine("err: $err");

    }

} else {

    Write-Host "Script ran fine!";

}



if ( @($global:PROGERR).length -gt 0 ) {

    # do stuff

} else {

    Write-Host "External program ran fine!";

}

A dull example however I am wondering if that is possible?

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.txt

if ($LastExitCode -ne 0) { ... handle error ... }

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

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] }

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

This is also an alternative that I have used to redirect stdout and stderr of a command line while still showing the output during PowerShell execution:

$command = "myexecutable.exe my command line params"



Invoke-Expression $command -OutVariable output -ErrorVariable errors

Write-Host "STDOUT"

Write-Host $output

Write-Host "STDERR"

Write-Host $errors

It is just another possibility to supplement what was already given.

Keep in mind this may not always work depending upon how the script is invoked. I have had problems with -OutVariable and -ErrorVariable when invoked from a standard command line rather than a PowerShell command line like this:

PowerShell -File ".FileName.ps1"

An alternative that seems to work under most circumstances is this:

$stdOutAndError = Invoke-Expression "$command 2>&1"

Unfortunately, you will lose output to the command line during execution of the script and would have to Write-Host $stdOutAndError after the command returns to make it "a part of the record" (like a part of a Jenkins batch file run). And unfortunately it doesn't separate stdout and stderr.