PSMonday #23: October 3, 2016

 Topic: Commands, Cmdlets, and Functions

Notice: This post is a part of the PowerShell Monday series — a group of quick and easy to read mini lessons that briefly cover beginning and intermediate PowerShell topics. As a PowerShell enthusiast, this seemed like a beneficial way to ensure those around me at work were consistently learning new things about Windows PowerShell. At some point, I decided I would share these posts here, as well. Here’s the PowerShell Monday Table of Contents.

Before we jump into the next topic, I think it would be wise to ensure we discuss the differences between commands, cmdlets, and functions. In doing that, we’ll also learn, or clarify, the differences between parameters, parameter names, and parameter values.

As we’ve learned, in a roundabout way, cmdlets and functions have the potential to include parameters. Scripts in fact, can also include parameters. A parameter is made up of a parameter name and a parameter value, or values.

A cmdlet, such as Get-Service, Stop-Process, Get-EC2Instance, and Set-ADUser, is likely written in C#, and is compiled code. A function, which can be written in a simple text editor, isn’t compiled, as the source can be easily read. These include Get-Volume, Get-Verb, New-SmbShare, and many more, including those we might write ourselves using the ISE, or Visual Studio Code. Those products are both better alternatives to using a simple text editor.

Let’s take a look at a command, break down each part, and then call it a day.

Get-EventLog -ComputerName DC01,DC02 -LogName Application -Verbose

Get-EventLog
This is the command. The term command can be used for just the cmdlet or function, or a cmdlet or function that includes parameters. You might also just call it by its CommandType: cmdlet or function. I’m not completely sure if it’s been mentioned before or not, but cmdlet is pronounced command-let.

-ComputerName DC01,DC02
This is a parameter.

-ComputerName
This is the parameter name.

DC01,DC02
These are the parameter values.

-LogName Application
This is also a parameter.

-LogName
This is the parameter name.

Application
This is the parameter value.

-Verbose
Even this, is a parameter.

Before we wrap up, I want to quickly discuss the last parameter mentioned: Verbose. There are parameter names that don’t require any specified parameter value be included. These are called switch parameters. If they’re included, their parameter value — even though you can’t see it — is True ($true), and if they’re not included, their parameter value is False ($false). Therefore, their default value is always $false.

Alright, back with more next time.

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