Centrally Stored Modules - Pt. 2 -Module Basics - Directories, Files, Functions and Module Manifest

Continuing on from the Module Basics explained in my Previous Post.

Lets look at some examples on the theory mentioned in the post.

We'll go ahead and create a new module called "MyModule" (we'll use the default folder paths for now)

1. Create a new folder called "MyModule" in one of the directories exposed to $env:PSModulePath

New-Item -Type Directory -Path "$Home\Documents\WindowsPowerShell\Modules\MyModule"

2. Inside the folder create a file called "MyModule.psm1"

New-Item -Type File -Path "$Home\Documents\WindowsPowerShell\Modules\MyModule\MyModule.psm1"

• IMPORTANT: The Directory name created in Step 1 and the File Name in step 2 Must Match in order for the Get-Module -ListAvailable commandlet to work!

3.Now lets create a Module Manifest (which is basically a hash table of information which gets loaded into your powershell scope at the time of running Import-Module).

New-ModuleManifest -Path "$Home\Documents\WindowsPowerShell\Modules\MyModule\MyModule.psd1"

• in Powershell 2.0 - Just running the above command will prompt for a bunch of Parameters to be entered - Enter as much or as little as you like.  What you enter here will be stored in the psd1 file.
• in Powershell 3.0 - Just running the above command simply creates the psd1 file which you need to manually edit later.
• IMPORTANT: When filling in the Module Manifest, for the Import-Module command to work, you MUST enter the top entry of the Hash Table.
• In PS v2 - this entry is called "ModuleToProcess"
• In PS v3 - this entry is called "RootModule"
• Make sure to uncomment any other values which you intend to fill out.

4. Now that we have the files Created, lets create some basic functions inside the module.  To ensure that i differentiate the functions which i write, to the functions which are powershell native, i am going to prefix the names with "My".  At this stage i'll leave these functions empty.

Function Get-MyProcess {

 }

 Function Get-MyService {

} 

5. So at this stage, we've created a module with 2 empty functions inside a module.  Now we need to expose these functions so that Powershell knows which commands to load into the Scope at the time of doing Import-Module.
There are 2 ways to do this:

• Using the Export-ModuleMember cmdlet
• To use this method, at the bottom of your MyModule.psm1 file, simply add

Export-ModuleMember -function Get-MyService 

Export-ModuleMember -function Get-MyService 

• Using the Module Manifest
• To use this method, open your MyModule.psd1 file, find the entry which reads "FunctionsToExport" and make it look like this:

FunctionsToExport = @("Get-MyProcess",
    "Get-MyService")

• Which method you chose is up to you, i prefer using the manifest as all the exposed information is kept within one file and is quite clear to read. 

6. Now we are ready to test importing our new module.

IMPORTANT: There is a distinct difference between powershell V2 and V3 in terms of how they handle importing modules.

• In PS V2 - you must use Get-Module -ListAvailable to find your module.  Once you have confirmed it is on the List you can then run:

Import-Module MyModule 

• in PS V3 - you dont have to, it already scans inside each module folder inside $env:PSModulePath and it knows about MyModule already.  Simply start typing in Get-MyProcess or Get-MyService and it will find it.

There you have it.  You now have your own module which can be listed as available and imported into your powershell session.