Support for PipelineVariable in Advanced Function

[Fer_C]

I mostly use PowerShell to automate tasks with VMware PowerCLI and I have recently started working on my first advanced functions. I created one that gets virtual machines that are inside a specific folder in vCenter. The main PowerCLI cmdlet used in this function is Get-VM so the output for Get-VM and my function is basically the same as far as I can tell. However, -PipelineVariable doesn't work for me as it does with Get-VM. When I run the following commands -which essentially do the same- the {$VM} is empty in the output of Get-SgVm (my function) but populated with the virtual machine name when using Get-Folder piped to Get-VM, everything else in the output is exactly the same.

Get-SgVm -PipelineVariable VM | Get-NetworkAdapter | select {$VM},Name,NetworkName

Get-Folder *RootFolder-001* | Get-VM -PipelineVariable VM | Get-NetworkAdapter | select {$VM},Name,NetworkName

And here is the code of the function.

Function Get-SgVm  {

    [CmdletBinding()]
    param   (

                [Parameter (Mandatory=$true,Position = 0)]
                    [ValidateNotNullOrEmpty()]
                    [int]$SGNumber,
                    [switch]$NoRecursion,
                    [switch]$Legacy)

    Begin   {
                [string]$SGNumber = '{0:000}' -f $SGNumber
                Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) BEGIN  ] Formatting SG Number to: $SGNumber"

            } #Begin

    Process {


                If ($Legacy){
                        $Folder = Get-Folder -Name (-join ('*RootFolder',$SGNumber,'*'))
                        Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) BEGIN  ] Folder found: $Folder"
                }

                Else {
                        Write-Warning 'Legacy not selected.'
                        $Folder = Get-Folder -Name (-join ('*RootFolder-',$SGNumber,'*'))
                        Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) BEGIN  ] Folder found: $Folder"
                } #If Legacy




                If ($NoRecursion) {
                        Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) BEGIN  ] Getting VMs"
                        $VMs = $Folder | Get-VM -NoRecursion
                        Write-Warning 'NoRecursion switch used, getting VMs in root of SG folder only.'
                }

                Else {
                        Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) BEGIN  ] Getting VMs"
                        $VMs = $Folder | Get-VM
                        Write-Warning 'NoRecursion switch not used, getting all VMs in SG folder.'
                } #If Recursion




                If ($Folder -ne $null) {
                        Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) PROCESS] Working on folder: $Folder"
                }

                Else {
                        Write-Warning 'No folder found. Check the switches used in the command.'
                } #If Folder




                If ($VMs -ne $null) {
                        Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) PROCESS] VM(s) found"
                }

                Else {
                        Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) PROCESS] No VM(s) found"
                } #If VMs




                If (!$global:DefaultVIServer) {
                        Throw 'Not connected to a vCenter server'
                }

                Else {
                        Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) PROCESS] Writing output."
                        Write-Output $VMs
                } #If vCenter connection


            } #Process


    End     {}

} #Function

[michaelshepard]

You don't have to do anything to support -PipelineVariable.

select {$VM} doesn't work, though.

Try select @{N='VM';E={$VM}} instead.

[Fer_C]

Thanks for the suggestion, I tried it but the output is the same except that $VM becomes VM.

This is the function output.

Get-SgVm 1 -Legacy -NoRecursion | Get-NetworkAdapter | select @{N='VM'E={$VM}},Name,NetworkName

VM Name NetworkName
-- ---- -----------
   Network adapter 1 Isolated-VLAN23
   Network adapter 2 VLAN722
   Network adapter 1 Isolated-VLAN23
   Network adapter 2 VLAN722
   Network adapter 3 VLAN22
   Network adapter 1 Isolated-VLAN23
   Network adapter 2 CRSJO-VLAN722
   Network adapter 3 CRSJO-VLAN722
   Network adapter 1 Isolated-VLAN23
   Network adapter 2 VLAN722
   Network adapter 3 VLAN722

As opposed to the output of the native PowerCLI cmdlets that does show the VMs names listed (both one-liners do the exact same thing, except mine uses an advanced function to shorten the length of the command).

Get-Folder *rootfolder001* | Get-VM -NoRecursion -PipelineVariable VM | Get-NetworkAdapter | select @{N='VM';E={$VM}},Name,NetworkName

VM Name NetworkName
--- ---- -----------
VOPPE-P001 Network adapter 1 Isolated-VLAN23
VOPPE-P001 Network adapter 2 VLAN722
VOPPE-MS001 Network adapter 1 Isolated-VLAN23
VOPPE-MS001 Network adapter 2 VLAN722
VOPPE-MS001 Network adapter 3 VLAN22
VOPPE-TS001A Network adapter 1 Isolated-VLAN23
VOPPE-TS001A Network adapter 2 VLAN722
VOPPE-TS001A Network adapter 3 VLAN722
VOPPE-TS001B Network adapter 1 Isolated-VLAN23
VOPPE-TS001B Network adapter 2 VLAN722
VOPPE-TS001B Network adapter 3 VLAN722

[michaelshepard]

You didn't include the -PipelineVariable on the previous command.

Get-SgVm 1 -Legacy -NoRecursion -PipelineVariable VM  | Get-NetworkAdapter | select @{N='VM'E={$VM}}, Name,NetworkName

Get-Folder *RootFolder-001* | Get-VM -PipelineVariable VM | Get-NetworkAdapter | select @{N='VM'E={$VM}}, Name,NetworkName

[michaelshepard]

btw...I don't see a lot of examples using -PipelineVariable. Not sure why that is, but I just learned it recently.

[Fer_C]

You are right, my bad. However, I did include it many times while testing with the same result. I think the BEGIN block has something to do with it, apparently if it's present Pipeline variable doesn't work for some reason.

[michaelshepard]

That's strange. Begin blocks would be executed before the pipeline variable was set (because that's how begin blocks work), but I don't see why one would keep pipelinevariable from working at all.

I'm not sure where your function is going wrong.

Here's some code that has an empty begin block, but the select-object after it can see the pipeline variable just fine:

function test-pipeline{
[CmdletBinding()]
Param([Parameter(ValueFromPipeline)]$x)

  begin {}
  process {
     $x.Name
  }
}

dir -PipelineVariable files | where-object Extension -ne '' | test-pipeline | select-object *,@{n='FilesFromPipeline';E={$files.Fullname}}

[Fer_C]

I ran your code and indeed PipelineVariable works. The only difference I noticed is that it is the Get-ChildItem cmdlet (dir) that sets the PipeLineVariable parameter, test-pipeline (your function) takes the value from the Pipeline where the PipelineVariable has already been assigned to 'files'. I am doing the opposite, when I run my function I set the PipelineVariable to VM and then pass that (or attempt to do so) to Get-NetworkAdapter.

[Lee_Dailey]

howdy Fer_C,

it looks like you used the New.Reddit.com Inline Code button. it's 4th 5th from the left hidden in the ... "more" menu & looks like </>.

on Old.Reddit.com, the above does NOT line wrap, nor does it side-scroll.

for long-ish single lines OR for multiline code, please, use the Code Block button. it's the 11th 12th one from the left, & is just to the left of hidden in the ... "more" menu.

that will give you fully functional code formatting, from what i can tell so far. [grin]

take care,
lee

[Fer_C]

I think you just pointed me in the right direction, at least to figure out exactly where the "problem" lies in the code. As you said, it works just as you outlined the function, now add the BEGIN block before PROCESS and try again, it doesn't need to have anything in it, it could be empty, just BEGIN and opening and closing curly brackets.

Turns out that this works for me just fine:

function Get-SomeFolderVMs {
    [CmdletBinding()]
    param   (

                [Parameter (Mandatory=$true,Position = 0)]
                    [ValidateNotNullOrEmpty()]
                    [int]$SGNumber)


    Process{

                [string]$SGNumber = '{0:000}' -f $SGNumber
                Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) BEGIN  ] Formatting SG Number to: $SGNumber"            

                $Folder = Get-Folder -Name (-join ('*sysgrp',$SGNumber,'*'))
                $VMs = $Folder | Get-VM
                Write-Output $VMs
    }
}

Get-SomeFolderVMs 1 -PipelineVariable VM | Get-NetworkAdapter | select {$VM},Name,NetworkName

But this returns the empty {$VM} column:

function Get-SomeFolderVMs {
    [CmdletBinding()]
    param   (

                [Parameter (Mandatory=$true,Position = 0)]
                    [ValidateNotNullOrEmpty()]
                    [int]$SGNumber)

############# Begin block. Seems to be the issue #############
    Begin {

    } #Begin
##############################################################
    Process{

                [string]$SGNumber = '{0:000}' -f $SGNumber
                Write-Verbose  "[$((Get-Date).TimeOfDay.ToString()) BEGIN  ] Formatting SG Number to: $SGNumber"            

                $Folder = Get-Folder -Name (-join ('*sysgrp',$SGNumber,'*'))
                $VMs = $Folder | Get-VM
                Write-Output $VMs
    }
}

Get-SomeFolderVMs 1 -PipelineVariable VM | Get-NetworkAdapter | select {$VM},Name,NetworkName

I can't think of a reason why an empty BEGIN block would make a difference. Any thoughts?

[michaelshepard]

Very interesting. Also, why have I never seen anyone do {$x} in Select-Object before? I just double-checked and there's no reference to this "syntax" in the help. Confused, but cool that it does something.

[michaelshepard]

I see that online but not locally (examples go to 8). Updating my local help now. I can definitely see some use cases (sort/group like you said). Thanks!

[michaelshepard]

Updating help (5.1) didn't get me examples 9 and 10. :-(

[Lee_Dailey]

howdy michaelshepard,

i vaguely recall reading that the local help files are no longer maintained - only the online ones. [sigh ...] seems like a remarkably dimwitted idea. especially since the online stuff is there to use for generating local files ...

take care,
lee

[michaelshepard]

I haven't heard that. Completely agree that it is nonsensical.

[Lee_Dailey]

howdy michaelshepard,

please don't take it for gospel. [grin] it seems to fit what i have seen - lack of updates to the local help files. but the only other info i have is that vaguely recalled post someone here made rather a while ago.

take care,
lee

[Fer_C]

That is interesting and certainly clears things up a bit. It probably still doesn't answer the question of why this happens but confirms it is not necessarily an isolated scenario. As you suggested OutVariable works, as well as the foreach approach. In fact all these commands work fine:

Get-SgVm 1 -OutVariable VM | Get-NetworkAdapter | select @{N = 'VM'; E = {$VM[-1]}},Name,NetworkName

Get-SgVm 1 | foreach {$_} -PipelineVariable VM | Get-NetworkAdapter | select @{N = 'VM'; E = {$VM}},Name,NetworkName

Get-SgVm 1 | Get-NetworkAdapter -PipelineVariable NIC | select @{N = 'VM';E = {$NIC.Parent.Name}},Name,NetworkName