PowerShell script always Pass, doesn't throw Error - "ErrorAction Stop" doesn't catch exception [duplicate]

Question

I have my silent installation PowerShell script but I have issue that even if some of the arguments are not correct my execution of the powershell script will not fail.

$expression="C:\app\tool.exe  /COMPUTER=server1  /INSTALL  /SILENT"
try {
Invoke-Expression $expression -ErrorAction Stop
}
catch {
Write-Host "Entered Exception"
}

Unfortunately it's always "green", like execution was successful and no Errors have been thrown.

In the log however I can see that it was "Unintended cancel" of the setup.

******************************************************** Error:
Connect to computer registry failed
Computer 'SERVER1' does not exist
The network path was not found.

Unattended setup >>> 'Cancel'
********************************************************
Exit code = 0x4C7

My script does not enter the catch clause. Is it possible that I can somehow force this to fail, so I can catch that error. I am having big issue that my powershell does not fail, although it should because it got wrong installation argument.

Thank you!!!

The explanation for this has been provided here: stackoverflow.com/questions/31086630/… — Aditya Nair
– Aditya Nair, Commented Oct 10, 2021 at 8:25
@AdityaNair is it related if I execute the script without Invoke-Expression? If I execute without Invoke-Expression I am getting exactly the same behaviour - I do not get any error "C:\app\tool.exe /COMPUTER=server1 /INSTALL /SILENT" Can you please tell me why it doesn't then throw error if I run .exe file directly? — vel
– vel, Commented Oct 10, 2021 at 8:30
Check for the output of $LASTEXITCODE at the end of execution of exe. if status is not 0, throw error. I have posted it in the answer for reference. — Aditya Nair
– Aditya Nair, Commented Oct 10, 2021 at 8:35
As an aside: Invoke-Expression (iex) should generally be avoided; definitely don't use it to invoke an external program or PowerShell script. — mklement0
– mklement0, Commented Oct 10, 2021 at 12:44
As of PowerShell 7.2, calls to external programs do not cause PowerShell errors (even via Invoke-Expression), which means that PowerShell's error-handling features (e.g. try { ... } catch { ... }) do not apply (except accidentally, due to a bug with redirections up to v7.1). Instead, check if $LASTEXITCODE is nonzero to determine whether an external program failed. Future PowerShell versions may offer an opt-in mechanism for integrating external-program calls into PowerShell's error handling. See the linked duplicate for details. — mklement0
– mklement0, Commented Oct 10, 2021 at 16:16

Aditya Nair · Accepted Answer · 2021-10-11 07:13:14Z

-1

Invoke-Expression only checks for the possibility to run a command and gives success when the command can be invoked. Use $LASTEXITCODE to check for output:

$expression="C:\app\tool.exe  /COMPUTER=server1  /INSTALL"
try {
    $result = Invoke-Expression $expression
    if ($LASTEXITCODE -ne 0) {
        throw $result
    }
}
catch {
    Write-Host "Entered Exception"
    $_
}

edited Oct 11, 2021 at 7:13

answered Oct 10, 2021 at 8:32

Aditya Nair

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5 Comments

vel Over a year ago

This does not help unfortunately. I still do not get any output. If I add some Write-Host it is being printed out but catch clause is not captured.

PS C:\> try {Write-Host "aaaa" >> $result = Invoke-Expression $expression >> Write-Host "bbb" >> if ($result -like "*not found*" -or $result -like "*Error*") { >>         throw $result >>     } >> } >> catch { >>     Write-Host "Entered Exception" >>     $_ >> }   aaaa bbb

Daniel Over a year ago

$LASTEXITCODE will work also with native app run with Invoke-Expression. To catch errors in the $result variable you need to redirect the error stream to the success steam $result = Invoke-Expression ($expression + " 2>&1")

vel Over a year ago

Thanks. The second solution by using the $LASTEXITCODE part works!!! ($reuslt like expression doesn't but when I use LASTEXITICODE I am getting what I need) Thanks a lot

mklement0 Over a year ago

I didn't down-vote, but I think your answer could be improved: Invoke-Expression should be advised against in general, and should especially be avoided for calling external programs. Success or failure should in general not be derived from an external program's output, but from its exit code (which makes your $LASTEXITCODE solution the proper one). Besides, in the case at hand, there's likely no (stdout/stderr) output at all (only log-file output), due to /SILENT.

Aditya Nair Over a year ago

I have modified the answer according to the working solution @AndreyDonald

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