Capture program stdout and stderr to separate variables - windows

Question

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 1

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] }

Answer 2

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.

Answer 3

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

Answer 4

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.

Answer 5

In case you want to get any from a PowerShell script and to pass a function name followed by any arguments you can use dot sourcing to call the function name and its parameters.
Then using part of James answer to get the $output or the $errors.
The .ps1 file is called W:\Path With Spaces\Get-Something.ps1 with a function inside named Get-It and a parameter FilePath.
Both the paths are wrapped in quotes to prevent spaces in the paths breaking the command.
$command = '. "C:\Path Spaces\Get-Something.ps1"; Get-It -FilePath "W:\Apps\settings.json"'
Invoke-Expression $command -OutVariable output -ErrorVariable errors | Out-Null
# This will get its output.
$output
# This will output the errors.
$errors

Answer 6

Copied from my answer on how to capture both output and verbose information in different variables.
Using Where-Object(The alias is symbol ?) is an obvious method, but it's a bit too cumbersome. It needs a lot of code.
In this way, it will not only take longer time, but also increase the probability of error.
In fact, there is a more concise method that separate different streams to different variable in PowerShell(it came to me by accident).
# First, declare a method that outputs both streams at the same time.
function thisFunc {
[cmdletbinding()]
param()
Write-Output 'Output'
Write-Verbose 'Verbose'
}
# The separation is done in a single statement.Our goal has been achieved.
$VerboseStream = (thisFunc -Verbose | Tee-Object -Variable 'String' | Out-Null) 4>&1
Then we verify the contents of these two variables
$VerboseStream.getType().FullName
$String.getType().FullName
The following information should appear on the console:
PS> System.Management.Automation.VerboseRecord
System.String
'4>&1' means to redirect the verboseStream to the success stream, which can then be saved to a variable, of course you can change this number to any number between 2 and 5.

Answer 7

Separately, preserving formatting
cls
function GetAnsVal {
param([Parameter(Mandatory=$true, ValueFromPipeline=$true)][System.Object[]][AllowEmptyString()]$Output,
[Parameter(Mandatory=$false, ValueFromPipeline=$true)][System.String]$firstEncNew="UTF-8",
[Parameter(Mandatory=$false, ValueFromPipeline=$true)][System.String]$secondEncNew="CP866"
)
function ConvertTo-Encoding ([string]$From, [string]$To){#"UTF-8" "CP866" "ASCII" "windows-1251"
Begin{
$encFrom = [System.Text.Encoding]::GetEncoding($from)
$encTo = [System.Text.Encoding]::GetEncoding($to)
}
Process{
$Text=($_).ToString()
$bytes = $encTo.GetBytes($Text)
$bytes = [System.Text.Encoding]::Convert($encFrom, $encTo, $bytes)
$encTo.GetString($bytes)
}
}
$all = New-Object System.Collections.Generic.List[System.Object];
$exception = New-Object System.Collections.Generic.List[System.Object];
$stderr = New-Object System.Collections.Generic.List[System.Object];
$stdout = New-Object System.Collections.Generic.List[System.Object]
$i = 0;$Output | % {
if ($_ -ne $null){
if ($_.GetType().FullName -ne 'System.Management.Automation.ErrorRecord'){
if ($_.Exception.message -ne $null){$Temp=$_.Exception.message | ConvertTo-Encoding $firstEncNew $secondEncNew;$all.Add($Temp);$exception.Add($Temp)}
elseif ($_ -ne $null){$Temp=$_ | ConvertTo-Encoding $firstEncNew $secondEncNew;$all.Add($Temp);$stdout.Add($Temp)}
} else {
#if (MyNonTerminatingError.Exception is AccessDeniedException)
$Temp=$_.Exception.message | ConvertTo-Encoding $firstEncNew $secondEncNew;
$all.Add($Temp);$stderr.Add($Temp)
}
}
$i++
}
[hashtable]$return = #{}
$return.Meta0=$all;$return.Meta1=$exception;$return.Meta2=$stderr;$return.Meta3=$stdout;
return $return
}
Add-Type -AssemblyName System.Windows.Forms;
& C:\Windows\System32\curl.exe 'api.ipify.org/?format=plain' 2>&1 | set-variable Output;
$r = & GetAnsVal $Output
$Meta2=""
foreach ($el in $r.Meta2){
$Meta2+=$el
}
$Meta2=($Meta2 -split "[`r`n]") -join "`n"
$Meta2=($Meta2 -split "[`n]{2,}") -join "`n"
[Console]::Write("stderr:`n");
[Console]::Write($Meta2);
[Console]::Write("`n");
$Meta3=""
foreach ($el in $r.Meta3){
$Meta3+=$el
}
$Meta3=($Meta3 -split "[`r`n]") -join "`n"
$Meta3=($Meta3 -split "[`n]{2,}") -join "`n"
[Console]::Write("stdout:`n");
[Console]::Write($Meta3);
[Console]::Write("`n");