Adds ModuleBase Post #15

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---
title: 'PowerShell Module Base for Config Files'
date: 2022-03-21T09:14:41+01:00
draft: false
categories: ['PowerShell']
tags: ['ModuleBase', 'config']
# lastmod: 2022-03-21T09:14:41+01:00
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---
![note](note.jpg 'Photo by [Sigmund](https://unsplash.com/@sigmund) on [Unsplash](https://unsplash.com)')
## 🖼️ Intro
Sometimes you want to use a basic config file for your module. This config file should be used to define basic
settings without any user specific content. This file could be placed into your PowerShell Module folder.
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 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 based config file:
```powershell
{
# 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 needed values:
```powershell
function Get-ConfigValue {
<#
.SYNOPSIS
Returns the value of a given config file key.
.PARAMETER ByKey
Config file key.
.OUTPUTS
[string]
.EXAMPLE
Get-ConfigValue -ByKey 'OutputLevel'
.NOTES
Private module helper function. Used by other function within your module.
#>
[CmdletBinding()]
[OutputType([string])]
param (
[Parameter(Mandatory = $true, HelpMessage = 'Existing key from config file.')]
[string]$ByKey
)
begin { }
process {
$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 $Config.$ByKey
}
catch {
Write-Error -Message $_.Exception.Message -ErrorAction Stop
}
}
else {
Write-Error -Message 'Config file not found!' -ErrorAction 'Stop'
}
}
end { }
}
```
## 💭 Final Thoughts
All you need to to is using the `Get-ConfigValue -ByKey '<example key>'` in your functions to get the 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 >}}
Keep in mind 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.
{{< /alert >}}

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