The Wiert Corner – irregular stream of stuff

I love the solution with piped Join-Path constructs answered by David Keaveny in [WayBack] powershell – How do I use join-path to combine more than two strings into a file path? – Stack Overflow:

Since Join-Path can be piped its path value, you can pipe multiple Join-Path statements together:

Join-Path "C:" -ChildPath "Windows" | Join-Path -ChildPath "system32" | Join-Path -ChildPath "drivers"

Of course you could replace the built-in [WayBack] Join-Path by using using the .NET Framework [WayBack] Path.Combine Method (System.IO), but then you loose code completion.

If you do like that, here is how:

[System.IO.Path]::Combine("C:", "Windows", "system32", "drivers")

–jeroen

This is my default PowerShell script header from now on:

Set-StrictMode -Version Latest
$ErrorActionPreference = 'Stop'
$PSDefaultParameterValues['*:ErrorAction']='Stop'

This might sound like overkill, but it solves these problems:

• Set-StrictMode -Version Latest will warn on uninitialised variables and other code risks; see for instance [WayBack] Enforce Better Script Practices by Using Set-StrictMode – Hey, Scripting Guy! Blog and [WayBack] Set-StrictMode
• $ErrorActionPreference = 'Stop' will raise exceptions when errors occur under almost all circumstances to you do not have to add -ErrorAction Stop in CmdLets; see for instance [WayBack] powershell – Why does the exception not get me in the catch block? – Stack Overflow
• $PSDefaultParameterValues['*:ErrorAction']='Stop'works around CmdLets that ignore $ErrorActionPreference = 'Stop'; see for instance [WayBack] windows – How to stop a PowerShell script on the first error? – Stack Overflow and [WayBack] error handling – PowerShell – Setting $ErrorActionPreference for the entire script – Stack Overflow

The above helped me tremendously with for instance [WayBack] powershell – Why does the exception not get me in the catch block? – Stack Overflow:

I’m trying to interrogate some service information. Sometimes the installer of the application fails to correctly install, so the registry does not contain a service entry. I want to find out which installer steps did get executed correctly, even on systems that do not have proper logging in the installer.

If MyService does not exist, the script below does not go to the catch block even though the exception handling documentation suggests a bare catch should be enough:

try {
    $path = 'hklm:\SYSTEM\CurrentControlSet\services\MyService'
    $key = Get-Item $path
    $namevalues = $key | Select-Object -ExpandProperty Property |
        ForEach-Object {
        [PSCustomObject] @{
            Name = $_;
            Value = $key.GetValue($_)
        }
    }
    $namevalues | Format-Table
}
catch {
    $ProgramFilesX86 = [System.Environment]::GetFolderPath("ProgramFilesX86");
    $ProgramFiles = [System.Environment]::GetFolderPath("ProgramFiles");
    Write-Host $ProgramFilesX86
    Write-Host $ProgramFiles
}

Why is that and how should I force it to end up in the catch?

This is what PowerShell outputs:

Get-Item : Cannot find path 'HKLM:\SYSTEM\CurrentControlSet\services\MyService' because it does not exist.
At C:\Users\Developer\...\GetMyServiceInfo.ps1:17 char:12
+     $key = Get-Item $path
+            ~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (HKLM:\SYSTEM\Cu...vices\MyService:String) [Get-Item], ItemNotFoundException
    + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetItemCommand

For which I edited the answer to become this:

Force the error to be terminating:

$key = Get-Item $path -ErrorAction Stop

That way it will throw and catch will get it.

Explanation and links to the official Microsoft documentation:

• -ErrorAction is a Common Parameter that can be applied to any PowerShell command
• The default value for -ErrorAction is Continue which prevented the exception to be thrown in the first place.
• You can configure a global -ErrorAction setting using the Preference Variable named $ErrorActionPreference to override this default value.

What is missing there is the link to the $PSDefaultParameterValues documentation at [WayBack] about_Parameters_Default_Values | Microsoft Docs

–jeroen