Using Module Scope

One of the most perplexing topics in PowerShell, especially for beginner scripters is scope. Referencing items like variables and functions that may or may not be available can feel spinning a roulette wheel. You probably know about things like the global and script scopes. But there's another scope that you may not think about often: the module scope. There's a reason we use a manifest or the Export-ModuleMember cmdlet. It's all about scope. Let's take a look at how module scope works and how you can use it to your advantage.

A PowerShell module typically consists of a set of functions and perhaps variables. When you import a module, PowerShell sets up a module scope. All commands from the module run in that scope. Where it gets tricky is that you'll see commands from the global scope. Here's a test module.

$fooVar = 100
Function Get-Secret {
    Param([string]$string)

    $n = $string.ToCharArray()
    for ($i = 0; $i -lt $fooVar; $i++) {
        $n = $n | Get-Random -Count $n.count
    }

    $n -join ''
}

Function Get-PSFoo {
    [cmdletBinding()]
    [alias('psf')]
    Param(
        [string]$Text
    )

    $space = ';',':','<','?','-','_' | Get-Random -count 1
    #replace all whitespace with a random character
    $Text = $Text -replace '\s',$space
    Write-Verbose "Running PSFoo on $Text using a value of $fooVar"
    Get-Secret -string $Text

}

I'll import his module.