Test for existence of an AD object in PowerShell using only Microsoft-provided cmdlets

Question

I want to test for the existence of a computer account in Active Directory with PowerShell using only tools from Microsoft.

Using Quest AD cmdlets, I can do this:

if (!(get-qadcomputer $name)){ Stuff }

That doesn't work with get-adobject or get-adcomputer as far as I can tell.

Is there something simple that I'm missing? I've seen a couple hacky-looking solutions that trap all exceptions that get thrown, but that seems like it could give some false positives under certain circumstances.

Solution 1

Have a look at this:

http://blogs.msdn.com/b/adpowershell/archive/2009/05/05/how-to-create-a-function-to-validate-the-existence-of-an-ad-object-test-xadobject.aspx

Solution 2

$c = Get-ADComputer <$ComputerName>
if($c -eq $null) { ItDoesntExist } else { ItLives }

This should do exactly what you need... you said it isn't working for you, why exactly?

---

Sorry, looks like this cmdlet actually throws an exception instead of simply returning $null, as documented here... and it also ignores the -erroraction parameter (scroll down to the comments on the linked page).

Suggested workaround:

$errorActionPreference = "SilentlyContinue"

Get-ADComputer <$ComputerName>

Or, better, see my other answer.

Comments

[MDMarra]

I get Get-ADComputer : Cannot find an object with identity: 'test' under: 'DC=my,DC=domain'. At line:1 char:20 + $c = Get-ADComputer <<<< "test" + CategoryInfo : ObjectNotFound: (test:ADComputer) [Get-ADComputer], ADIdentityNotFoundException + FullyQualifiedErrorId : Cannot find an object with identity: 'test' under: 'DC=my,DC=domain'.,Microsoft.ActiveDirectory.Ma nagement.Commands.GetADComputer when running it against a machine that doesn't exist.

[Zoredache]

Maybe do something with -erroraction? Suppress the error and test for it?

[Massimo]

Ops. Looks like it's a known (and frustrating) issue: blogs.technet.com/b/askds/archive/2010/02/04/… (scroll down to the comments).

[MDMarra]

Yeah, not returning $null like a good cmdlet is what's been killing me. I'm trying out your other answer now, though.

[Avi Pars]

Would this work with Get-ADComputer?

[Johan de Haan]

This works with a lot of cmdlets which return an object or not. If it returns an object (or more) and you cast it to type boolean it will become a true, without an object returned it will become a false.