dusz dusz - 4 months ago 13
PowerShell Question

Powershell: Capture program stdout and stderr to seperate variables

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?

Answer

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 exes.