Blog/content/posts/psmodulebase/index.md

title	date	categories	tags
How to get and use your PowerShell Module Base.	2022-03-21T09:14:41+01:00	PowerShell	ModuleBase config

🖼️ Intro

This article explains with a practical example how to determine and use the current module base path:

Sometimes you want to use a basic config file for your module. This config file could be used to define basic settings for your module. These module wide default settings should placed and shipped within your module.

Therefore you can use the automatic variable $MyInvocation, especially with its properties $MyInvocation.MyCommand.Module.ModuleBase. This returns the full path to your current module base folder, which can be used by your function to join a path for your config file.

📑 .\config.psd1 config file

Let's assume you start a new module and you need multiple config keys to work with. So you usually create a JSON or PowerShell Data format based config file:

{
    # Logging
    OutputLevel         = 'Detailed'
    DefaultTarget       = 'Console'
    LogRetentionInWeeks = 4

    # DataSource
    CouchDBURI = 'http://localhost'
    MongoDBURI = 'http://mongodb'

    # ...
    # ...
}

🔎 Get-ConfigValue helper function

Now you can use $MyInvocation.MyCommand.Module.ModuleBase with a helper function to parse the path to your config file and return your stored default values:

function Get-ConfigValue {
    <#
    .SYNOPSIS
        Returns the value of a given config file key.

    .PARAMETER FromKey
        Config file key.

    .OUTPUTS
        [string]

    .EXAMPLE
        Get-ConfigValue -FromKey 'OutputLevel'

    .NOTES
        Private module helper function. Used by other function within your module.
    #>

    [CmdletBinding()]
    [OutputType([string])]
    param (
        [Parameter(Mandatory = $true, HelpMessage = 'Existing key from config file.')]
        [string]$FromKey
    )

    begin { }

    process {
        $ErrorActionPreference = 'Stop'
        $ModuleBase = $MyInvocation.MyCommand.Module.ModuleBase
        $ConfigFile = Join-Path -Path $ModuleBase -ChildPath 'config.psd1'

        if (Test-Path -Path $ConfigFile) {
            try {
                $Config = Import-PowerShellDataFile -Path $ConfigFile
                Write-Output $Config.$FromKey
            }
            catch {
                Write-Error -Message $_.Exception.Message
            }
        }
        else {
            Write-Error -Message 'Config file not found!'
        }
    }

    end { }
}

💭 Final Thoughts

All you need to to is using the Get-ConfigValue -FromKey '<example key>' in your functions to get any value defined in you config file.

As far as I know, that's the simplest way to get your module root and using it with a config file.

{{< alert >}} Do not to store any sensitive data in you config file. User specific data should also be stored in a user context and not in a global module wide config file. {{< /alert >}}