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So with that, let's jump into PowerShell and let me

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show you variables in action.

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Okay, I have a Windows 10 desktop running the latest build of

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PowerShell 7.0, and so let's go through and look at some ways of

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working with variables, just kind of the basics here.

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First off, the most basic, Get‑Variable. This is a command you can run to

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see all of the variables that are defined in your current PowerShell

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session. Variables can be referenced by their name,

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that you see there with a dollar sign in front of it.

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For example, I can say show me the variable, $PSVersionTable.

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This is a handy variable, by the way, because it shows you what

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version you're running, so I'm running PowerShell version 7.1.3, and

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you can see I'm on a Windows desktop. And there are other variables

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like $pwd, which is the current working directory, or $HOME, which is

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your user's home directory.

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You can use Get‑Variable to get the variable value, but don't do this. This is

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going to fail, and that's because even though we are in the habit of referencing

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variables with their dollar sign in front of it,

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the dollar sign is not technically part of the name.

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So normally what you would want to do if you're using Get‑Variable is just the

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name without the dollar sign, and then you can see the value.

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This is an object, so if I pipe this to say Select all,

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I can see all of the properties of this variable object.

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So the variable itself is an object, but really what we

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care about and what you're going to see is using the stuff

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that is inside the variable.

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A $pid is another built‑in variable.

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This is the process ID of your current PowerShell session.

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And just to show you, if I pipe $pid to Get‑Member, the value, because

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it's an integer, you can see that the type name that Get‑Member shows me

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is a System.Int32. It's not a variable object,

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it's whatever is in that variable.

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That's what really matters.

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So I can use that variable as a placeholder instead of me having trying to

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figure out what's my process ID, you just use $pid to Get‑Process, and I

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can get that to work with really no problem.

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There is an about topic that you should take some time

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to look at, help about_Variables.

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I'm not going to go through that.

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You can run that command on your own.

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Now, let's quickly look at creating some variables.

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It's as simple as typing $, whatever the variable name is, equals

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whatever you want to assign it a value to. So I'm going to set $a =

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2, and I can reference that just by typing $a. I can create a new

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variable $n, say, = to foo.

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And you can use variables to hold the output from commands.

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So I'm going to run a command called Get‑Vegetable.

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This is part of a module of mine called PS Teaching Tools

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that you can download from the PowerShell Gallery, I've got

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notes in the course downloads.

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This is a tool that I wrote just to provide me a generic

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command that writes objects to the pipeline without anything

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special like file or processes.

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And if I look at that, I can see, sure enough there are some vegetable objects.

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Now, technically, you can also create variables with New‑Variable.

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So I can say I want to create a variable called ver and give it a value of 1,

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and then reference that by $ver, and you can see that it is 1.

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There are some advanced things that you can do with this command if you

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need it, but really more of a special case, but let me at least demonstrate

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them so you have them in the back of your head.

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You can use New‑Variable to create a variable and give it an option, say

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ReadOnly, provides a little safety mechanism from someone changing the value

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or you accidentally changing the value of a variable.

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Or you can also create a variable that is considered a Constant.

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So I'll create a variable pi and give it a value of

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3.14, and that is now a Constant.

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So there's $user and $pi.

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So you can see that they work just the way that you would

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expect them to like any other variable.

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But, let's try to change variables now.

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So I've got $n, up above you see it was foo, now I'm going to change it to bar.

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And that works really no problem at all, because I haven't done anything

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special. Raise my version level to 2, and now $ver is 2.

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But, now let's look at those special variables I

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created, the user and pi variables.

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If I try to assign a new value to user, such as Gladys,

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I get an error, and that says, hey,

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I can't do this because you made that read‑only or a constant.

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Now in this case, because it's read‑only, there is an option that you can

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do using Set‑Variable, and use the ‑force parameter. And I'm using

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‑PassThru so it writes the new result to the pipeline.

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This allows me to modify the value of that ReadOnly variable, but I had to

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take specific steps and really tell PowerShell, hey,

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I know what I'm doing and I want this value to chain.

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However, this won't work with things that are constants.

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That doesn't work.

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You'll have to delete the variable and recreate it if you want to reuse the

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variable with the name of pi. And real quickly on the subject of variable

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names, give your variables names that are meaningful. If you're just working

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interactively in the console, you know, they can be short,

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because you don't want to have to type a lot, although you do

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have tab expansion, but you want to make sure that the

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variable names are meaningful to you.

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They should just be alphanumeric, don't include spaces,

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there's no need for dashes or underscores, just very simple

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names should be all that you need.

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If you want to get rid of a variable,

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you can use Clear‑Variable. So this is going to leave the

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variable, but it will remove the value. So you can see the

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variable is still there, but it is empty.

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There is a cmdlet called Remove‑Variable that will completely delete

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the variable from your PowerShell session, and now the veg variable is

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gone and will no longer be available to me.

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If I try to run Get‑Variable,

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you can see I get an error, well, not really an error, it

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says I can't find a variable with that name.

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Now, one thing that's important here, that did not change the source here.

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If I can still do Get‑Vegetable c*, which is what I used to create the

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vegetable variable, those things are still there, so the variable is just

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kind of a placeholder to hold the results. It doesn't change, there's nothing really linked up or anything like that.