Variables: `$name`

A variable is a name PowerShell keeps a value under, so $owl = "…" stores a long path once, $drawings = Get-ChildItem … keeps a whole list of files, and $owl hands the value back in any later command until you close the window.

Apprentice · PowerShell · Updated

After this lesson you can

  • Store a value or a command's answer in a variable with $name = …, and use it in later commands
  • Explain what a variable holds once it's set, a snapshot that changes only when you set it again, and why a mistyped name gives nothing

Key takeaways

  • $owl = '…' puts a value in a box called owl. $owl, read "the value of owl", hands it back in any later command.
  • A variable can hold a command's whole answer: $drawings = Get-ChildItem … keeps the file objects, properties and all.
  • A variable is a snapshot: it doesn't change when the folder does, until you set it again.
  • Names ignore capital letters. A name you never set is empty, not an error, so a typo quietly gives you nothing.
  • Your variables last until you close the window. $HOME and $PSVersionTable are PowerShell's own, filled in for you.

You're working in a folder five levels deep, and you've typed its path so often your fingers know it, typos included. Or you listed a folder's files, and now you want to sort that same list a second way without asking for it again. Or a guide says "save the result of this command, you'll need it in a minute." Each time, you want PowerShell to remember something for you. That's what a variable is for, and every script in this course is built on them. A help-desk tech keeps a computer's name in one while fixing it; a web developer keeps a project's folder in one.

Set up the workshop

This chapter's practice folder is a workshop. Ada Wren, an inventor, keeps her machines there (they're tiny PowerShell scripts), and her newest project, a clockwork owl, sits four folders deep. Copy these lines into PowerShell. They print nothing when they work, and running them again is safe:

New-Item -ItemType Directory -Force -Path "$HOME\terminal-practice\workshop\tools", "$HOME\terminal-practice\workshop\projects\clockwork-owl\drawings" | Out-Null
Set-Location "$HOME\terminal-practice\workshop"
Set-Content letter.txt 'Back from the inventors'' fair on December 4. Keep the machines running! - Ada'
Set-Content kettle-bot.ps1 'if ($env:POWER -eq "on") { "Pouring tea..." } else { "NO POWER" }'
Set-Content tools\oil.ps1 '"Glug, glug. The gears are oiled and shining."'
Set-Content projects\clockwork-owl\drawings\wings.txt 'Wings: 12 brass feathers each, hinged at the shoulder'
Set-Content projects\clockwork-owl\drawings\beak.txt 'Beak: copper, opens on the hour'
Set-Content projects\clockwork-owl\drawings\gears.txt 'Gears: 7 teeth on the small one, 21 on the big one, 3 turns to 1'

A name for a value: `$owl = …`

Picture a box with a label on it. The label is the variable's name, and what you put inside is its value. In PowerShell every variable's name starts with $, and = puts a value in the box:

$owl = "$HOME\terminal-practice\workshop\projects\clockwork-owl"
$owl

C:\Users\Sam\terminal-practice\workshop\projects\clockwork-owl

Read the first line as "put this path in the box called owl". It printed nothing: PowerShell quietly kept the value. The second line is the variable on its own, and $owl is read "the value of owl", so PowerShell shows what's in the box. (The double quotes let $HOME fill in your home folder; the next lesson, Text: Quotes and $( ), shows how.)

Now $owl works anywhere you'd type the path. Set-Location $owl takes you there, and this lists the owl's drawings:

Get-ChildItem "$owl\drawings"

    Directory: C:\Users\Sam\terminal-practice\workshop\projects\clockwork-owl\drawings

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---           11/7/2026 10:15 AM             33 beak.txt
-a---           11/7/2026 10:15 AM             66 gears.txt
-a---           11/7/2026 10:15 AM             55 wings.txt

Your dates and times will be the moment you made the practice folder.

A whole answer in a box

A variable can hold a command's answer too. Here the box holds the three file objects themselves, with every property from What an Object Is: Get-Member, so you can count them and sort them without asking the disk again:

$drawings = Get-ChildItem "$owl\drawings"
$drawings.Count
$drawings | Sort-Object Length -Descending | Select-Object Name, Length

3

Name      Length
----      ------
gears.txt     66
wings.txt     55
beak.txt      33

A variable is a photo, not a window. Add a drawing to the folder, and the box still holds the three files it got:

Set-Content "$owl\drawings\tail.txt" 'Tail: 9 brass feathers, fanned'
$drawings.Count
$drawings = Get-ChildItem "$owl\drawings"
$drawings.Count

3
4

Only when you set the variable again does it see the fourth file. Setting a variable replaces what was in the box; +=, read "add to", adds to what's there. $cups = 0, then $cups += 1 twice, leaves 2 in $cups.

Names and typos

Names ignore capital letters: $OWL and $owl are the same box. Use letters, digits and underscores; a dash looks like the start of a parameter, so PowerShell stops:

$gear-size = 7

ParserError:
Line |
   1 |  $gear-size = 7
     |       ~~~~~
     | Unexpected token '-size' in expression or statement.

$gearSize, with a capital letter where each new word starts, is the usual way to write a name of two words.

A mistyped name is a quieter problem. A box you never filled is empty, so $owel prints nothing at all, with no error to warn you. When a command does something strange, check your variable's spelling first.

PowerShell's own variables

Some boxes are filled before you type anything. $HOME is your home folder, $PSVersionTable says which PowerShell you're running, and $_ is "this item" from Filtering: Where-Object and Comparisons. They're automatic variables, so don't use their names for your own. Get-Variable shows a box's name and its value, without the $:

Get-Variable owl

Name                           Value
----                           -----
owl                            C:\Users\Sam\terminal-practice\workshop\projects\clockwork-owl

Your own variables last until you close the window. A new window starts with empty boxes; Your Profile, in the next chapter, shows how to fill some every time PowerShell starts. Everything here works the same in Windows PowerShell 5.1 and on a Mac or Linux, where paths use /.

Try it. Put your Downloads folder in a variable with $dl = "$HOME\Downloads", then count the files in it with (Get-ChildItem $dl -File).Count.

Check yourself

2 questions to try on the lesson page.

So what

A variable lets PowerShell remember for you: a path you'd rather not retype, or a whole command's answer to sort and count again and again. Scripts are built from them, starting in this chapter.

Key terms

Cheat sheets

Related