powershell - How to properly use the -verbose and -debug parameters in a custom cmdlet

Question

By default, any named function that has the [CmdletBinding()] attribute accepts the -debug and -verbose (and a few others) parameters and has the predefined $debug and $verbose variables. I'm trying to figure out how to pass them on to other cmdlet's that get called within the function.

Let's say I have a cmdlet like this:

function DoStuff() {
   [CmdletBinding()]

   PROCESS {
      new-item Test -type Directory
   }
}

If -debug or -verbose was passed into my function, I want to pass that flag into the new-item cmdlet. What's the right pattern for doing this?

Answer 1

$PSBoundParameters isn't what you're looking for. The use of the [CmdletBinding()] attribute allows the usage of $PSCmdlet within your script, in addition to providing a Verbose flag. It is in fact this same Verbose that you're supposed to use.

Through [CmdletBinding()], you can access the bound parameters through $PSCmdlet.MyInvocation.BoundParameters. Here's a function that uses CmdletBinding and simply enters a nested prompt immediately in order examine the variables available inside the function scope.

PS D:> function hi { [CmdletBinding()]param([string] $Salutation) $host.EnterNestedPrompt() }; hi -Salutation Yo -Verbose

PS D:>>> $PSBoundParameters

____________________________________________________________________________________________________
PS D:>>> $PSCmdlet.MyInvocation.BoundParameters

Key Value                                                                                                                                                                                                           
--- -----                                                                                                                                                                                                           
Salutation Yo                                                                                                                                                                                                              
Verbose   True                                                                                       

---

So in your example, you would want the following:

function DoStuff `
{
    [CmdletBinding()]
    param ()
    process
    {
      new-item Test -type Directory `
        -Verbose:($PSCmdlet.MyInvocation.BoundParameters["Verbose"].IsPresent -eq $true)
    }
}

This covers -Verbose, -Verbose:$false, -Verbose:$true, and the case where the switch is not present at all.