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Powershell has Start-Process cmdlet (start a new process) which can be a new powershell and get it to run whatever e.g. via -Command & {scriptblock} .

Limitation on/after ‘-Command ‘ of 32,760 chars ( due to underlying UNICODE_STRING usage?) . However you can supply Start-Process with a -Credential ( to run under ), in which circumstance the limitation on/after the ‘-Command’ appears to drop to 1024.

Can anyone help me by explaining why this is ? If it should be and if it's documented anywhere ?

( And without using fixed other script, or passing of arguments to said code via a file, how best to overcome ? )

Code to repro:-


$username = "Domain\User" 
$password = "************"
$useCred = New-Object System.Management.Automation.PSCredential -ArgumentList @($username,(ConvertTo-SecureString -String $password -AsPlainText -Force))

$Nof = 32000
$spaces = (" "*$Nof)
write-host -NoNewLine "test with OUT Credential, command at least $Nof in length"
try { Start-Process Powershell -NoNewWindow -ArgumentList "-Command & $spaces{}"  ; write-host " - OK"} 
catch {write-host " - FAIL"; throw $_ }

$Nof = 800
$spaces = (" "*$Nof)
write-host -NoNewLine "test WITH Credential, command at least $Nof in length"
try { Start-Process Powershell -NoNewWindow -Credential $useCred -ArgumentList "-Command & $spaces{}" ; write-host " - OK"} 
catch {write-host " - FAIL"; throw $_ }

$Nof = 1000
$spaces = (" "*$Nof)
write-host -NoNewLine "test WITH Credential, command at least $Nof in length"
try { Start-Process Powershell -NoNewWindow -Credential $useCred -ArgumentList "-Command & $spaces{}" ; write-host -NoNewLine " - OK"} 
catch {write-host " - FAIL"; throw $_ }

Result:

test with OUT Credential, command at least 32000 in length - OK
test WITH Credential, command at least 800 in length - OK
test WITH Credential, command at least 1000 in length - FAIL
Start-Process : This command cannot be run due to the error: The parameter is incorrect.
At ......\test_F.ps1:22 char:7
+ try { Start-Process Powershell -NoNewWindow -Credential $useCred -Arg ...
+       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Start-Process], InvalidOperationException
    + FullyQualifiedErrorId : InvalidOperationException,Microsoft.PowerShell.Commands.StartProcessCommand
Improve this question
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  • The error is the parameter is incorrect. The length doesn't have anything to do with the error. Why are you using curly brackets after $spaces? Where is the argument list? Commented Jul 31, 2024 at 15:50
  • The code is just a repro in reality there'd be actual code within the {scriptblock} and possibly arguments/parameter provision for it after. The $spaces could probably be put later in the code but for demo purposes it shows the issue there. The 3 test cases showing the difference between having no -Credential and having some -Credential, then that it works with a longish (800) line but not when go over 1000 (1024 presumed). Commented Aug 1, 2024 at 19:01
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