01 · Setup & First Script

PowerShell today means PowerShell 7+ (also called "PowerShell Core"), built on .NET and run with the pwsh executable. It's open source and cross-platform — the same scripts run on Windows, macOS, and Linux. This is different from Windows PowerShell 5.1, the older, Windows-only, built-in version (powershell.exe). Throughout this course, "PowerShell" means PowerShell 7+ unless noted otherwise.

Installing PowerShell 7+

# Windows (winget)
winget install --id Microsoft.PowerShell --source winget

# macOS (Homebrew)
brew install --cask powershell

# Linux (Ubuntu/Debian) — see Microsoft's docs for your distro's exact steps
sudo apt-get install -y powershell

Verify the install:

pwsh --version
# PowerShell 7.4.1

Starting a session

Launch pwsh from any terminal to get an interactive session — a REPL (Read-Eval-Print Loop) where you can type commands one at a time and see results immediately.

pwsh
# PowerShell 7.4.1
# PS /Users/you>

# try a built-in cmdlet right away
Get-Date

# Expected output (abbreviated)
Saturday, July 20, 2026 9:12:03 AM

Your first script file

Scripts live in .ps1 files. Create one with any text editor:

# hello.ps1
Write-Host "Hello, PowerShell!"
Write-Output "This line is returned as output, not just printed."

Run it:

pwsh ./hello.ps1
# or, from inside an already-running pwsh session:
./hello.ps1

Hello, PowerShell!
This line is returned as output, not just printed.

Write-Host writes directly to the console (for humans) and cannot be captured or piped onward. Write-Output sends an object down the pipeline — it can be captured in a variable, piped to another cmdlet, or redirected to a file. Prefer Write-Output (or simply letting an expression's result fall through) for anything that might be consumed by other code; reserve Write-Host for pure console messages like progress notes.

Execution policy

On Windows, PowerShell blocks running local scripts by default as a safety measure. Check and adjust it with:

Get-ExecutionPolicy
# Restricted

# Allow locally-created scripts to run for the current user only
Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy RemoteSigned

RemoteSigned is the common safe default: local scripts run freely, but scripts downloaded from the internet must be digitally signed. macOS and Linux builds of pwsh do not enforce this policy the same way, so you'll mostly encounter it on Windows.

Comments and basic syntax

# a single-line comment

<#
  a block comment,
  spanning multiple lines
#>

Write-Output "PowerShell statements don't need a trailing semicolon,"
Write-Output "but you can use one to put two statements on one line."; Write-Output "like this"

The help system

PowerShell's built-in help is one of its best features — every cmdlet is self-documenting.

Get-Help Get-Process
Get-Help Get-Process -Examples
Get-Help Get-Process -Full

# first time only, to download the latest help content
Update-Help

# discover cmdlets by keyword
Get-Command -Noun Process

CommandType     Name                    Version    Source
-----------     ----                    -------    ------
Cmdlet          Get-Process             7.0.0.0    Microsoft.PowerShell.Management
Cmdlet          Stop-Process            7.0.0.0    Microsoft.PowerShell.Management
...

Cheat sheet

Command	Purpose
pwsh	start an interactive PowerShell 7+ session
pwsh ./script.ps1	run a script from the shell
Get-ExecutionPolicy / Set-ExecutionPolicy	check / change script-running permissions
Write-Output	send an object down the pipeline
Write-Host	print directly to the console (not pipeable)
Get-Help <cmdlet>	show documentation for a cmdlet
Get-Command -Noun <thing>	find cmdlets related to a noun

How It Actually Works

pwsh is not "the Windows console with new commands" — it's a hosted .NET process. When you launch it, the executable spins up a runspace: a CLR AppDomain-hosted environment containing a session state (variables, functions, aliases, drives) and an engine that parses and executes commands against it. Every PowerShell host — the console, the ISE, VS Code's terminal, a remote session — is just a different front end creating and talking to a runspace through the same System.Management.Automation API.

When you type a line and press Enter, three distinct stages run before anything happens on screen:

1. Tokenizing/parsing — the engine's parser (not a shell-style word splitter) builds an Abstract Syntax Tree (AST) from the line, using PowerShell's actual grammar: pipelines, statements, expressions, command-parameter-argument triples. This is why Get-Process | Stop- + half a cmdlet name gives you a real parse error, not a "command not found" from a shell.
2. Command resolution — the parser hands each command element to the engine's command discovery service, which searches, in order: functions in the current session state, aliases, cmdlets registered by loaded modules, then external executables on PATH. This ordering is why you can define a function named ls that silently wins over the built-in alias.
3. Execution — the AST is compiled (in PowerShell 5+/7, actually JIT-compiled via expression trees for hot code, not purely tree-walked) and run. Cmdlets are .NET classes implementing Cmdlet/PSCmdlet with BeginProcessing/ProcessRecord/EndProcessing methods called by the pipeline processor — this is why every cmdlet supports the pipeline uniformly, unlike shell tools that only understand text streams.

Cross-platform pwsh (built on .NET, formerly .NET Core) achieves the same behavior on macOS/Linux/Windows by shipping the whole engine as managed code rather than shelling out to OS-specific APIs — the handful of Windows-only cmdlets (like Get-WmiObject) are the exceptions that rely on Windows-specific COM/WMI interop unavailable on other platforms.

🔀 See this in another language

• Python — Setup & First Program
• C# — What Is C# & .NET?
• Kotlin — Setup & First Program

Exercise

Write greet.ps1 that uses Write-Output to print a greeting, then calls Get-Date and stores the result in a variable, then prints a second message that includes that variable so it reads something like "Generated on <date>.". Run it with pwsh ./greet.ps1 and confirm both lines appear.