Wednesday, January 18, 2017

Using Get-CimAssociatedInstance

Tonight I finally found a use for the Get-CimAssociatedInstance cmdlet. I know what that cmdlet does, but never had a real use case, until tonight. 

What I was trying to do was to use the CIM cmdlets to find the logged-on user. 

Initially, I searched through the many Win32_Classes and found one that looked promising (Win32_LogonSession). So I tried looking at the interactive logons:
Get-CimInstance Win32_LogonSession |         Where-Object LogonType -EQ 10
But that returned me a somewhat unhelpful response:

I wanted the username (and the SID). So I searched around a bit and found a class name that looked appealing: win32_loggedonuse. Turns out this is one an associator class. In WMI, the associator associates two other instances in the WMI database. In this case. the associator class associates a Win32_LogonSession with the WIn32_Account that is logged on in that session.

So I turned it into a tool :.
Function Get-WhoIAm {
# Get Account for the loggede on user$Me = Get-CimINstance Win32_LogonSession |         Where-Object LogonType -EQ 10 |           Get-CimAssociatedInstance -Association win32_loggedonuser
# Extract useful properties$IAmHT = [ordered] @{}$IAmHT.Account            = $Me.Caption$IAmHT.Description        = $Me.Description$IAmHT.LocalAccount       = $Me.LocalAccount$IAmHT.PasswordChangeable = $me.PasswordChangeable$IAmHT.SID                = $Me.SID$IamHT.CommputerName      = (Get-CimInstance -Classname Win32_Computersystem).Name
# Create a new object$IAm = New-Object -TypeName PSCustomObject -Property $IAmHT
# And return the Iam objectreturn $IAm
And for fun, I set an alias of WhoAmi - a tool I've used for a decade or longer. With that done, the output looks like this:

Happy days with WMI and the CIM Cmdlets.

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