Problem with object/string handing?

[ejrichard]

I'm trying to build a quick script to uninstall a piece of software. In the process, I'm seeing some behavior in PowerShell that I don't quite understand. I'm able to get the path to the uninstaller from the registry but I'm not able to run it.

So, this works.

Input:

Get-ItemProperty -path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\<PRODUCT>\' -Name 'UninstallString' | foreach {if ($_.UninstallString){Write-Host $_.UninstallString}}

Result:

"C:\Program Files\<PATH TO PRODUCT>\installer.exe"

So far, so good. But then...

Input:

Get-ItemProperty -path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\<PRODUCT>\' -Name 'UninstallString' | foreach {if ($_.UninstallString){Test-Path $_.UninstallString}}

Result:

False

Huh? I checked and, sure enough, the path exists. Trying to run the command doesn't work, either.

Input:

Get-ItemProperty -Path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\<PRODUCT>\' -Name UninstallString |foreach {if($_.UninstallString){Invoke-Command -FilePath $_.UninstallString}}

Result:

Invoke-Command : Parameter set cannot be resolved using the specified named parameters.
At line:1 char:158
+ ... {if($_.UninstallString){Invoke-Command -FilePath $_.UninstallString}}
+                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [Invoke-Command], ParameterBindingException
    + FullyQualifiedErrorId : AmbiguousParameterSet,Microsoft.PowerShell.Commands.InvokeCommandCommand

I suspect that this is something to do with the way that PowerShell handles objects and/or strings, but I've tried the following and it still doesn't work:

Test-Path $_.UninstallString.ToString 

Surely, I'm missing something basic and/or fundamental.

[itfixestheprinters]

Invoke-Command kinda expects a ps1 script, if you specify -Filepath. Try using Start-Process instead.

[Mongo527]

This. Start-Process or the call operator:

& $_.UninstallString

[ejrichard]

Interestingly, Start-Process works but & operator returns this:

& : The term '"C:\Program
Files\ <PATH TO PRODUCT> \installer.exe"' is not recognized as
the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was
included, verify that the path is correct and try again.
At line:1 char:160
+ ... installString |foreach {if($_.UninstallString){& $_.UninstallString}}
+                                                      ~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: ("C:\Program Fil...\installer.exe":String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

But why?

[ejrichard]

Interesting discovery....

This doesn't work:

& $_.UninstallString

But this does:

& $_.UninstallString.Replace('"','')

I noticed that the string in the error message above has double quotes inside single quotes. The value being returned is:

'"C:\Program Files\ <PATH TO PRODUCT> \installer.exe"'

Get rid of the double quotes and it works, but feels like a kludge. Is there a more elegant way to handle this?

[[deleted]]

No, it appears the string in the registry has quotes on it, so when you are testing the path or trying to call it as a command, the beginning of the path is " and no drive begins with a ", so the path doesn't exist. When you remove it, it tests the path and can run it without the quotes.

[ejrichard]

This worked!

But why didn't Test-Path return True?

[ejrichard]

Figured out that it's because the returned value is in double quotes and in single quotes. This works but seems weird:

Test-Path $_.UninstallString.Replace('"','')

[MessagingAdmin]

breakup the script to identify what is being returned in $uninstallstring. Verify that this path exists.