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Now in addition to everything I've shown you about variables,

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you know,

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you've seen how easy it is to create them and use them as

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placeholders and do variable expansion, there are some advanced things,

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at least advanced from you as a beginner in PowerShell that

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you might want to work with variables.

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And these are things such as Tee‑Object,

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which is a cmdlet,

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which I'll show that allows you to basically pipe an

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expression to the pipeline and also to a variable.

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We're going to look in a moment here about OutVariable and then a more

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complex and advanced topic that I debated putting in,

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but I just want to show it to you because you may see this in examples,

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and I want you to at least have a rough understanding of how this works,

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and that is the PipelineVariable.

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So Tee‑Object, which has an alias of Tee, is pretty simple to use.

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You run any command you want on the left side of the pipe character, so I'm

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going to do Get‑Process ls*, and pipe that to Tee‑Object,

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and I'm going to assign the variable p to hold the results.

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So what's going to happen is if I run this in a PowerShell session,

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I will get the expression result, the process result will show on the screen,

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and I'll also have it saved to a variable,

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$p.

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So what will happen is I can run Get‑Process,

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see the results, and save the results to a variable.

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It looks like this.

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I get my processes that start with Ls,

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and the results have been saved to a variable,

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$p.

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So I can take $p, it's the placeholder that holds the results, and say,

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hey,

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I want to measure say the working set and get the sum of

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those ls processes. Pretty simple.

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So using Tee‑Object is a nice way to get the results and also

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save them to a variable all in one command.

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Now kind of related to Tee‑Object is OutVariable.

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OutVariable is a common parameter,

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which means all PowerShell commands and advanced

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functions will include ‑outvariable.

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In this situation,

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what's happening is I'm using $p that I had from my Tee‑Object example,

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and then I'm going to pipe this again to measure‑object.

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But this time, I'm going to save the results also to a variable, m.

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So the only thing that goes to $m will be the results

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of that measure‑object command.

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This is a nice way of saving output from an individual pipeline segment.

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It comes in very handy when you're troubleshooting or

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debugging why a command does not work.

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So I can use $m and say show me the sum property of that value.

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Now I could've also used Tee‑Object, but I wanted to demonstrate OutVariable.

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This is a parameter I use often in my PowerShell work and

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something I think you'll use as well.

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And there you can see, I have the value of the sum property of the variable $m,

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which is the measurement object.

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I hope you can kind of follow all of that.

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The last item related to variables is another common

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parameter called the PipelineVariable.

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Now this is admittedly an advanced concept,

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so don't feel that this makes your head hurt that you're

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doing something wrong or you're not up to it.

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I rarely use PipelineVariable.

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This allows you to save pipeline segment output across the pipeline and

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then reuse it in another part of the pipeline expression.

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Sounds confusing.

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It is confusing.

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Don't worry too much about it,

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but at least I want you to see what is happening here.

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What we're getting is a temporary, in essence,

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in‑memory variable,

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so I only kind of walk through what's happening here on the screen.

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So I'm getting the numbers 1 to 5.

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So that's the range operator, the dot dot.

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For each of those numbers, it's going to foreach‑object.

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And foreach‑object I'm just displaying the value 12345.

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That's in the parentheses, I'm sorry, that's in the curly braces and the {$_}.

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However,

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I'm also saving the output of foreach‑object as an in‑memory variable to $a,

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‑pipelinevariable a.

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So now I'm piping the numbers 1 through 5.

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I then pipe those results to another foreach‑object and

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save that variable to pipeline b.

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And this pipeline expression is taking the number 1

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through 5 and then multiplying it by 2.

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And then at the very end,

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I'm piping those results to another foreach‑object where

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I'm just displaying { "$a * 2 = $b"}.

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Now, in this case, I'm using that variable expansion to create a string.

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I admit this is an artificial example,

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but hopefully you can kind of see what is going on here.

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Let's look at the results.

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So $a is 12345, and that's as it comes through the pipeline,

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$b is then the results of $a, or basically,

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the first number times 2.

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It gets a little complicated.

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Again, this is for special use case scenarios.

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It's an advanced topic you may not use all the time.

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There are often other ways to get the job done

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without resorting to PipelineVariable, but if you need to use it, it is there.