Powershell - verify object exists in AD

Question

i have a text file containing arround 100 servers, how can i push these into a script and test if they exist within AD? I have a simple script below:

$serverlist = get-content ServerList.txt
foreach ($server in $serverlist) {
    if (Get-ADComputer $serverlist ) {
        Write-Host "#########################"  
        Write-Host "Computer object exists"
        Write-Host "#########################"  
    }
    else {
        Write-Host "#########################"  
        Write-Host "Computer object NOT FOUND"
        Write-Host "#########################"
    }
}

the above does not work returning a error:

Get-ADComputer : Cannot convert 'System.Object[]' to the type 'Microsoft.ActiveDirectory.Management.ADComputer' required by parameter 'Identity'. Specified method is not supported.

Can someone please explain does the get-adcomputer only allow a single object? Also if i remove the txt file and add a server shown below:

if (Get-ADComputer "server name" )

The above provides only results if the server exists within AD, if the server does not the error is shown below:

Get-ADComputer : Cannot find an object with identity: 'iuiub' under: 'DC=####,DC=#####,DC=#####'

Thank you for any insight / help!

Phil

Solution 1

Create an array - @(). If the array has 1 or more objects in it - which is $true - then you know the computer exists. If the array has 0 objects in it - which is $false- then you know the computer doesn't exist. I know some people don't like the ErrorAction to be set to SilentlyContinue but you're "Outputting an Error" if an error does occur.

$serverlist = get-content ServerList.txt
foreach ($server in $serverlist) {
    if (@(Get-ADComputer $server -ErrorAction SilentlyContinue).Count) {
        Write-Host "#########################"  
        Write-Host "Computer object exists"
        Write-Host "#########################"
    }
    else {
        Write-Host "#########################"  
        Write-Host "Computer object NOT FOUND"
        Write-Host "#########################"
    }
}

Another thing you could try are try catch blocks. Sorta like this:

$serverlist = get-content ServerList.txt
foreach ($server in $serverlist) {
    try{
        Get-ADComputer $server -ErrorAction Stop
        Write-Host "#########################"  
        Write-Host "Computer object exists"
        Write-Host "#########################"
    }
    catch{
        Write-Host "#########################"  
        Write-Host "Computer object NOT FOUND"
        Write-Host "#########################"
    }
}

Solution 2

Line 3, change $serverlist to $server

With regards to handling a not found result. I'd try flipping the logic :

 $serverlist = get-content ServerList.txt
 foreach ($server in $serverlist) {
    $tempVar = Get-ADComputer $server
    if ($tempVar -like "Get-ADComputer : Cannot find an object with identity" ) {
      Write-Host "#########################"  
      Write-Host "Computer object NOT FOUND"
      Write-Host "#########################"  
    }
    else{
       Write-Host "#########################"  
       Write-Host "Computer object exists"
       Write-Host "#########################"
    }
}  

Comments

[Loïc MICHEL]

you can test result like that : if ( (Get-ADComputer "server1") -eq $null){"not found"} else {"alive"}

[Richard]

thank you for the comment kayasax, though i have tried this and this does not work for a computer object that does not exist, it reports a error and writes out "alive" even if it doesnt exist - thank you for the reply :)

[E.V.I.L.]

You need to use the ErrorAction parameter for Get-ADComputer. You need to let it know what you want it to do if there is an error.

[Richard]

Thank you for the advice, the extra line allows me to pipe out computer objects that exist! just still having problems with objects that do not exist within the domain... thank you for the help.

[Richard]

wow... this had me going for ages and i did end up trying the "try & catch" blocks but my syntax was not correct. Thank you, went with the second option.. works a treat. cheers!

[Patrick Burwell]

I still get 'Get-ADComputer : Cannot find an object with identity:' errors. How do you stop this?