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

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.

Answer 2

Perhaps it sounds strange, but there isn't any easy way for a cmdlet to know its verbose or debug mode. Take a look at the related question:
How does a cmdlet know when it really should call WriteVerbose()?
One not perfect, but practically reasonable, option is to introduce your own cmdlet parameters (for example, $MyVerbose and $MyDebug) and use them in the code explicitly:
function DoStuff {
[CmdletBinding()]
param
(
# Unfortunately, we cannot use Verbose name with CmdletBinding
[switch]$MyVerbose
)
process {
if ($MyVerbose) {
# Do verbose stuff
}
# Pass $MyVerbose in the cmdlet explicitly
New-Item Test -Type Directory -Verbose:$MyVerbose
}
}
DoStuff -MyVerbose
UPDATE
When we need only a switch (not, say, a verbosity level value) then the approach with $PSBoundParameters is perhaps better than proposed in the first part of this answer (with extra parameters):
function DoStuff {
[CmdletBinding()]
param()
process {
if ($PSBoundParameters['Verbose']) {
# Do verbose stuff
}
New-Item Test -Type Directory -Verbose:($PSBoundParameters['Verbose'] -eq $true)
}
}
DoStuff -Verbose
It's all not perfect anyway. If there are better solutions then I would really like to know them myself.

Answer 3

There is no need. PowerShell already does this as the code below proves.
function f { [cmdletbinding()]Param()
"f is called"
Write-Debug Debug
Write-Verbose Verbose
}
function g { [cmdletbinding()]Param()
"g is called"
f
}
g -Debug -Verbose
The output is
g is called
f is called
DEBUG: Debug
VERBOSE: Verbose
It is not done as direct as passing -Debug to the next cmdlet though. It is done through the $DebugPreference and $VerbrosePreference variables. Write-Debug and Write-Verbose act like you would expect, but if you want to do something different with debug or verbose you can read here how to check for yourself.

Answer 4

Here's my solution:
function DoStuff {
[CmdletBinding()]
param ()
BEGIN
{
$CMDOUT = #{
Verbose = If ($PSBoundParameters.Verbose -eq $true) { $true } else { $false };
Debug = If ($PSBoundParameters.Debug -eq $true) { $true } else { $false }
}
} # BEGIN ENDS
PROCESS
{
New-Item Example -ItemType Directory #CMDOUT
} # PROCESS ENDS
END
{
} #END ENDS
}
What this does different from the other examples is that it will repsect "-Verbose:$false" or "-Debug:$false". It will only set -Verbose/-Debug to $true if you use the following:
DoStuff -Verbose
DoStuff -Verbose:$true
DoStuff -Debug
DoStuff -Debug:$true

Answer 5

You could build a new hash table based on the bound debug or verbose parameters and then splat it to the internal command. If you're just specifying switches (and aren't passing a false switch, like $debug:$false) you can just check for the existence of debug or verbose:
function DoStuff() {
[CmdletBinding()]
PROCESS {
$HT=#{Verbose=$PSBoundParameters.ContainsKey'Verbose');Debug=$PSBoundParameters.ContainsKey('Debug')}
new-item Test -type Directory #HT
}
}
If you want to pass the parameter value it's more complicated, but can be done with:
function DoStuff {
[CmdletBinding()]
param()
PROCESS {
$v,$d = $null
if(!$PSBoundParameters.TryGetValue('Verbose',[ref]$v)){$v=$false}
if(!$PSBoundParameters.TryGetValue('Debug',[ref]$d)){$d=$false}
$HT=#{Verbose=$v;Debug=$d}
new-item Test -type Directory #HT
}
}

Answer 6

The best way to do it is by setting the $VerbosePreference. This will enable the verbose level for the entire script. Do not forget to disable it by the end of the script.
Function test
{
[CmdletBinding()]
param($param1)
if ($psBoundParameters['verbose'])
{
$VerbosePreference = "Continue"
Write-Verbose " Verbose mode is on"
}
else
{
$VerbosePreference = "SilentlyContinue"
Write-Verbose " Verbose mode is Off"
}
# <Your code>
}

Answer 7

You can set the VerbosePreference as a global variable on starting your script and then check for the global variable in your custom cmdlet.
Script:
$global:VerbosePreference = $VerbosePreference
Your-CmdLet
Your-CmdLet:
if ($global:VerbosePreference -eq 'Continue') {
# verbose code
}
Checking explicitly for 'Continue' allows the script to be equal to -verbose:$false when you call the CmdLet from a script that doesn't set the global variable (in which case it's $null)

Answer 8

You do not have to do any checks or comparisons. Even though -Verbose (and -Debug) are of type [switch], they seem to understand not just $true and $false but also their preference variable. The preference variable also gets inherited correctly to all child functions that are called. I tried this on Powershell version 7.3.2 and it works as expected.
function Parent {
[CmdletBinding()]param()
Child
}
function Child {
[CmdletBinding()]param()
New-Item C:\TEST\SomeDir -Force -ItemType Directory -Verbose:$VerbosePreference -Debug:$DebugPreference
}
Parent -Verbose
Parent -Debug

Answer 9

I think this is the easiest way:
Function Test {
[CmdletBinding()]
Param (
[parameter(Mandatory=$False)]
[String]$Message
)
Write-Host "This is INFO message"
if ($PSBoundParameters.debug) {
Write-Host -fore cyan "This is DEBUG message"
}
if ($PSBoundParameters.verbose) {
Write-Host -fore green "This is VERBOSE message"
}
""
}
Test -Verbose -Debug