content/posts/psmodulebase/index.md

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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
+# showDateUpdated: true
+
+# custom overrides for pages
+# showDate: false
+# showAuthor: false
+# showWordCount: false
+# showReadingTime: false
+# showTableOfContents: false
+# showTaxonomies: false
+# showEdit: false
+# sharingLinks: [null]
+---
+
+![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 >}}