0xB0Lesson 12 of 17

Scripts and modules

Save code as .ps1 scripts with parameters, share functions by dot-sourcing and modules, and install modules from the gallery.

26 min 7-question quiz 2 code exercises

By the end of this lesson you can

Write and run .ps1 scripts with their own param() block, and understand execution policy
Reuse functions by dot-sourcing and by building a .psm1 module
Find and install modules from the PowerShell Gallery, and customize your $PROFILE

A script is a .ps1 file. Run it by path: .\Get-Report.ps1 (or ./Get-Report.ps1). The .\ matters - PowerShell never runs scripts from the current folder by bare name, so a malicious ls.ps1 can’t hijack ls.

A script can start with its own param() block, exactly like a function, and then takes parameters: .\Get-Report.ps1 -Enclosure volcano -Days 7. Inside, $PSScriptRoot is the folder the script lives in - use it to find files that sit next to the script.

scripts.ps1

1$folder = Join-Path ([IO.Path]::GetTempPath()) "scripts-$(Get-Random)"
2New-Item -ItemType Directory -Path $folder | Out-Null
3Set-Content -Path (Join-Path $folder 'Get-Welcome.ps1') -Value @'
4param(
5  [Parameter(Mandatory)][string]$Name,
6  [int]$Times = 1
7)
8foreach ($i in 1..$Times) { "Welcome, $Name!" }
9'@
10& (Join-Path $folder 'Get-Welcome.ps1') -Name 'Skyla' -Times 2
11$script = Join-Path $folder 'Get-Welcome.ps1'
12& $script 'Pebble'

Output

Welcome, Skyla!
Welcome, Skyla!
Welcome, Pebble!

The & is the call operator: it runs a command whose name or path is in a string or variable. You need it whenever the path is computed or contains spaces - & "C:\Dragon Tools\report.ps1".

Running a script normally gives it its own scope: when it ends, its variables and functions disappear. Two ways to keep them:

Dot-sourcing: . .\helpers.ps1 (a dot, a space, then the path) runs the file in your scope, so its functions stay defined. Quick, but everything it defines leaks in.
Modules: a .psm1 file of functions. Import-Module .\Dragons.psm1 loads it, and Export-ModuleMember chooses which functions are public - helpers stay private. Put a module folder in one of the paths in $env:PSModulePath and it even loads automatically the first time you call one of its commands.

module.ps1

1$folder = Join-Path ([IO.Path]::GetTempPath()) "module-$(Get-Random)"
2New-Item -ItemType Directory -Path $folder | Out-Null
3$modulePath = Join-Path $folder 'Dragons.psm1'
4Set-Content -Path $modulePath -Value @'
5function Get-Roar { param([string]$Name) "$Name says $(Get-RoarSound)" }
6function Get-RoarSound { 'RAAAWR' }
7Export-ModuleMember -Function Get-Roar
8'@
9Import-Module $modulePath
10Get-Roar -Name 'Ember'
11[bool](Get-Command Get-Roar -ErrorAction SilentlyContinue)
12[bool](Get-Command Get-RoarSound -ErrorAction SilentlyContinue)
13(Get-Module Dragons).ExportedFunctions.Keys -join ','
14Remove-Module Dragons

Output

Ember says RAAAWR
True
False
Get-Roar

The module’s public function can still call its private helper, but you can’t. That’s encapsulation.

Thousands of ready-made modules live on the PowerShell Gallery (powershellgallery.com): Find-Module *azure* searches it and Install-Module Pester -Scope CurrentUser installs one for just you. (PowerShell 7.4 adds the faster Install-PSResource.) Popular picks: Pester for testing, PSScriptAnalyzer for linting, Az for Azure and Microsoft.Graph for Microsoft 365.

Finally, your profile - the script at $PROFILE - runs every time PowerShell starts. It’s the place for your favorite aliases, functions and prompt tweaks. notepad $PROFILE (or code $PROFILE) opens it; create it first with New-Item -Force $PROFILE if it doesn’t exist.

Key takeaways

Run scripts by path (.\script.ps1); give them a param() block; use $PSScriptRoot for nearby files.
The call operator & runs a command or script whose path is in a variable.
Dot-source (. .\file.ps1) to load functions into your scope; build a .psm1 module to share them properly.
Install-Module gets modules from the PowerShell Gallery; $PROFILE customizes every session.

Lesson quiz

7 questions · pass with 5 correct · up to 50 XP

Passing this quiz completes the lesson and keeps your streak going. Questions you miss come back in review sessions later.

Practice: write PowerShell scripts

Write a script in the editor and run it for real against sample input, which is piped into your script as $input. Scripts run on PowerShell 6.2 through Try It Online (tio.run), a free public service, so these exercises avoid PowerShell 7-only syntax; your script and test input are sent there.

Exercise 1

A script with parameters

+25 XP

Finish the script file the starter writes, Get-Enclosure.ps1, so that it has a param() block with a mandatory -Name and a -Size that must be small, medium or large (default medium), and outputs Ember needs a medium enclosure.

Then, for each input line (Name or Name Size), call the script with the call operator &, passing -Size only when the line has one.

Three dragons

script.ps1

Loading editor…

Lessons teach PowerShell 7; your script runs on PowerShell 6.2 via Try It Online (tio.run), a free public service, so stick to syntax that works there. Test input is piped into your script as $input. Your script and test input are sent to that service.

Exercise 2

Build a module

+25 XP

Write a module Keepers.psm1 (the starter saves it to a temporary folder) containing two functions:

Get-ShiftKeeper -Hour <int> returns Ada for hours 6-13, Grace for 14-21 and Linus otherwise.
Test-DayShift - a private helper (not exported) that Get-ShiftKeeper may use.

Export only Get-ShiftKeeper. The provided code imports the module, looks up each input hour, and checks the helper is hidden.

Around the clock