Handling errors when querying computer accounts - powershell

Question

Im using this script to retrieve the OU for a list of computers. When a computer doesn't exist, I get an error:
Cannot index into a null array.
At C:\tools\scripts\get-OU5.ps1:35 char:5
+ $dn = $result.Properties["distinguishedName"]
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : NullArray
When I manually searched for the computer on the domain, it didn't exist. Also, after the error occurs, it lists the previous OU value it received from the last computer, as the result for this computer that gives the error.
I know there are error handling abilities in PowerShell, but I'm just not sure on where to put the error handling and then also report it as the result in the output.

Answer 1

I would use the following script to retrieve the information. It uses the built-in error handling capabilities in PowerShell:
function Get-ComputerProperties{
[CmdletBinding()]
#requires -version 3
param(
[parameter(ParameterSetName = "ComputerName", Mandatory = $true, ValueFromPipeline = $true, Position = 0)]
$ComputerName
)
begin{
Import-Module ActiveDirectory
function Get-ADParent ([string] $dn) {
$parts = $dn -split '(?<![\\]),'
$parts[1..$($parts.Count-1)] -join ','
}
}
process {
$result = $Null
try{
$result = Get-ADComputer -Filter {Name -eq $ComputerName} -ErrorAction Stop
if($result){
New-Object PSObject -Property #{"Name" = $ComputerName; "OU" = (Get-ADParent $result.DistinguishedName)}
}
} catch {
Write-Warning "Error while retrieving Computer properties for ComputerName $Computername ($($_.Exception.Message))"
}
}
end{
Remove-Module ActiveDirectory
}
}
You can use the script in the following way:
Get-ComputerProperties -ComputerName "Computer1"
or
"Computer1","Computer2" | Get-ComputerProperties
or with a text file:
Get-Content "C:\computers.txt" | %{ Get-ComputerProperties }