Function

PowerShell Help
1

When running this function this line doesnt appear to execute 

 Get-WmiObject -Class win32_Bios -ComputerName $computername | Select-Object -Property SerialNumber
does not run. Any idea why?

function Get-RegisterType {

     [cmdletbinding()]

     Param(

     [Parameter(Mandatory=$True)]
     [string]$computername

     )

     if (Test-Connection -ComputerName $computername -Quiet -Count 1) {

     Write-Host "$computername is online" -ForegroundColor Green -BackgroundColor Black
          
     Get-WmiObject -Class win32_ComputerSystem -ComputerName $computername | Select-Object -Property Model, Name
     Get-WmiObject -Class win32_Bios -ComputerName $computername | Select-Object -Property SerialNumber
}

     else { Write-Host "$computername is not online.  Please look in LANDesk to determine register type." -ForegroundColor Red -BackgroundColor Black }

}

; Get-RegisterType
2

what makes you think that?

And, if you’ve run it without specifying a computer name, what is your expectation for the output?

3

Sorry, forgot to include the output

PS C:\Software\Scripts> .\Get-RegisterType.ps1
cmdlet Get-RegisterType at command pipeline position 1
Supply values for the following parameters:
computername: 20061sure03
20061sure03 is online

Model Name

4800E42 20061SURE03

It outputs this 

Get-WmiObject -Class win32_ComputerSystem -ComputerName $computername | Select-Object -Property Model, Name

but not this 

Get-WmiObject -Class win32_Bios -ComputerName $computername | Select-Object -Property SerialNumber

4

And if you just run:

Get-WmiObject -Class win32_Bios -ComputerName 20061sure03 | Select-Object -Property SerialNumber

In the console, do you get output?

5

Yes.

PS C:\Software\Scripts> Get-WmiObject -Class win32_Bios -ComputerName 20061sure03 | Select-Object -Property SerialNumber

SerialNumber
------------
41TGV23
6

So, when you write a function in PowerShell, there are a few standards you want to try to comply with.

One, don’t write messages directly to Host. Your Write-Hosts should really be Write-Verbose; run your command with -Verbose to see that output.

Two, you need to output one thing, and one thing only, to the pipeline. Right now you’re trying to emit two things.

     $cs = Get-WmiObject -Class win32_ComputerSystem -ComputerName $computername 
     $bios = Get-WmiObject -Class win32_Bios -ComputerName $computername 
     $props = @{Computername = $computername
                Model = $cs.model
                Name = $cs.name
                SerialNumber = $bios.serialnumber}
     New-Object -Type PSObject -Prop $props

When you’re querying multiple sources, you want to combine whatever you want into a single output thing. This is part of the fundamental narrative of “Learn PowerShell Scripting in a Month of Lunches,” if you’d like to dive into it in more detail. I use the above example, almost exactly, throughout the entire book, in fact.

7

Powershell is implicitly outputting to format-table. So after it has one set of columns decided on, it won’t display another set of columns. This was a gotcha for me when I was learning.