What is Module in PowerShell?

As per docs.microsoft.com, A module is a package that contains PowerShell members, such as cmdlets, providers, functions, workflows, variables, and aliases. The members of this package can be implemented in a PowerShell script, a compiled DLL, or a combination of both. These files are usually grouped together in a single directory.

In simple, PowerShell Modules allows us to organize our functions and use them in other scripts or PowerShell modules allow you to combine multiple scripts to simplify code management, accessibility, and sharing. Mostly many PowerShell scripters are slow to take that step of building a module. This allows you to be able to use the same code in many places without copying and pasting to code all over the place.

When do I create a PowerShell module?

• When the same script needs to be used more than once.
• if we need to break it apart into functions because it’s getting too complex to be in a single script.
• If we need to share the code with others. 

In this post, you can learn Step-by-step instructions on creating and using modules.

STEP #1 Starting with a PowerShell Function

A PowerShell Module can store any number of functions. To create a new module, we need to start creating a PowerShell Function. When your scripts get large, you start using more functions. These functions could be from someone else or functions that you write yourself. These functions start collecting at the top of your script.

In the below example, we creating a function called Get-BIOSInfo which will output the system BIOS information for the specific system. 

function Get-BIOSInfo
{
param($ComputerName)
Get-WmiObject -ComputerName $ComputerName -Class Win32_BIOS
}

Get-BIOSInfo -ComputerName localhost

STEP #2 Create a separate Folder for Custom Module 

All the custom Modules need to save under the Module folder, mostly the location will be C:\Program
Files\WindowsPowerShell\Modules. We need to create a separate folder for our Module so here we creating a folder called Get-BIOSInfo as shown below.

STEP #3 Save the Function as Module with .psm1 extension 

Next, we need to save our function under the Get-BIOSInfo folder. Most important thing is, the Folder name must match the Module name. Now I’ve got the Get-BIOSInfo module saved/created, and I’ve called it Get-BIOSInfo.psm1. Now I can ask my team to use it,

To make our function into Module, the file needs to be saved with .psm1 extension as shown below,

STEP #4 Test-Driving Your Module

PowerShell has automatically loaded your new module and made all of its commands available. Executing the Get-Module cmdlet will show your module just contains one function Get-BIOSInfo. To understand what just has happened, I had ran the below Get-Module cmdlet and shown the output below.

STEP #4 Finally, Import your Module to utilize in any script

Open a different PowerShell window, or open a new PowerShell (console or ISE). Your command Get-BIOSInfo is available immediately! It is now a standard PowerShell command just like the other commands you use. Importing the module brings all of the functions and variables into each user’s PowerShell session.

Note:

• PowerShell caches Modules so once you have loaded and used a module in a PowerShell session, any changes to the module will not become effective. To see changes, either use the module in a new PowerShell Host or force a complete module to reload:
• The module name should not be the name of your function. It should be a generic name such as a topic because later you will want to store more functions into your module.
• Do not use special characters or whitespace in your module name.
• A PowerShell Module can store any number of functions.

Conclusion

Having the option to create a Module in PowerShell directly is super handy and we can be really flexible in our day to day DevOps or other automation tasks.