123 lines
3.3 KiB
Markdown
123 lines
3.3 KiB
Markdown
---
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title: 'How to get and use your PowerShell Module Base.'
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date: 2022-03-21T09:14:41+01:00
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#draft: true
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categories: ['PowerShell']
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tags: ['ModuleBase', 'config']
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# lastmod: 2022-03-21T09:14:41+01:00
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---
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 on [Unsplash](https://unsplash.com)')
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## 🖼️ Intro
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This article explains with a practical example how to determine and use the current module base path:
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Sometimes you want to use a basic config file for your module. This config file could be used to define basic
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settings for your module. These module wide default settings should placed and shipped within your module.
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Therefore you can use the automatic variable `$MyInvocation`, especially with its properties
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`$MyInvocation.MyCommand.Module.ModuleBase`. This returns the full path to your current module base folder, which
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can be used by your function to join a path for your config file.
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## 📑 `.\config.psd1` config file
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Let's assume you start a new module and you need multiple config keys to work with. So you usually create a
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**JSON** or **P**ower**S**hell **D**ata format based config file:
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```powershell
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{
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# Logging
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OutputLevel = 'Detailed'
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DefaultTarget = 'Console'
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LogRetentionInWeeks = 4
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# DataSource
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CouchDBURI = 'http://localhost'
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MongoDBURI = 'http://mongodb'
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# ...
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# ...
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}
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```
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## 🔎 `Get-ConfigValue` helper function
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Now you can use `$MyInvocation.MyCommand.Module.ModuleBase` with a helper function to parse the path to your config
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file and return your stored default values:
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```powershell
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function Get-ConfigValue {
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<#
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.SYNOPSIS
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Returns the value of a given config file key.
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.PARAMETER FromKey
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Config file key.
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.OUTPUTS
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[string]
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.EXAMPLE
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Get-ConfigValue -FromKey 'OutputLevel'
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.NOTES
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Private module helper function. Used by other function within your module.
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#>
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[CmdletBinding()]
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[OutputType([string])]
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param (
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[Parameter(Mandatory = $true, HelpMessage = 'Existing key from config file.')]
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[string]$FromKey
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)
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begin { }
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process {
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$ErrorActionPreference = 'Stop'
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$ModuleBase = $MyInvocation.MyCommand.Module.ModuleBase
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$ConfigFile = Join-Path -Path $ModuleBase -ChildPath 'config.psd1'
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if (Test-Path -Path $ConfigFile) {
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try {
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$Config = Import-PowerShellDataFile -Path $ConfigFile
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Write-Output $Config.$FromKey
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}
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catch {
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Write-Error -Message $_.Exception.Message
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}
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}
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else {
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Write-Error -Message 'Config file not found!'
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}
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}
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end { }
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}
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```
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## 💭 Final Thoughts
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All you need to to is using the `Get-ConfigValue -FromKey '<example key>'` in your functions to get any value
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defined in you config file.
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As far as I know, that's the simplest way to get your module root and using it with a config file.
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{{< alert >}}
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Do not to store any sensitive data in you config file. User specific data should also be stored in a user
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context and not in a global module wide config file.
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{{< /alert >}}
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