Exercise: Back Up While You Sleep

This is the chapter in one job: a backup of your school work that happens every evening, whether you remember or not, and tells you the truth about how it went. Backup-SchoolWork.ps1 copies a school-work folder with robocopy, but only when you run it yourself, from its own folder, and answer its question. Your job is to make it safe to run with nobody there, then build the scheduled task that runs it at 6 PM. A Pester check runs your script the way a task would, from another folder with nobody to answer, and tells you which jobs are done.

Windows only: robocopy and scheduled tasks are part of Windows.

Get the exercise code

Open this lesson's GitHub repository, github.com/ask-codey/exercise-powershell-back-up-while-you-sleep, also linked from the Exercise box beside the lesson. Click Code, then Download ZIP, and unzip it into your terminal-practice folder. Or clone it with Git.

The folder holds:

• Backup-SchoolWork.ps1: the backup script, with jobs 1 to 7 as numbered comments.
• New-BackupTask.ps1: builds the scheduled task, with jobs 8 to 10. It hands the task back and registers nothing.
• school-work/: practice files to back up.
• Check.Tests.ps1: the check. You don't need to change it.

What to do

Open PowerShell in the exercise folder, the one with Check.Tests.ps1 in it, and open it in VS Code with code .. First, test the script the way Scripts That Run Without You did, with the task's own command:

pwsh -NoProfile -NonInteractive -File .\Backup-SchoolWork.ps1
$LASTEXITCODE

Read-Host: C:\Users\Sam\terminal-practice\exercise-powershell-back-up-while-you-sleep\Backup-SchoolWork.ps1:16
Line |
  16 |  $answer = Read-Host 'Back up school-work now? (y/n)'
     |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     | PowerShell is in NonInteractive mode. Read and Prompt functionality is not available.

0

Nothing was backed up, and the exit code says it worked. Then, one job at a time:

1. Full paths. $Source and $Destination default to school-work and backup in the script's own folder, built from $PSScriptRoot.
2. No one to answer. The question goes.
3. A log. A Write-Log function adds a dated line to logs\backup.log beside the script, and prints it too.
4. A transcript. Start-Transcript records each run in logs\last-run.txt.
5. Never mirror nothing. A missing or empty source folder is logged, and the script stops with exit code 1 before robocopy runs.
6. The mirror. robocopy mirrors with /MIR /R:2 /W:5 /NP, and -Rehearse adds /L.
7. An honest exit code. robocopy's code below 8 is exit 0, and 8 or more is exit 1, with a log line either way.
8. The task. Jobs 8 to 10 are in New-BackupTask.ps1: a trigger for every day at 6 PM, an action that runs pwsh.exe -NoProfile -NonInteractive -File with the script's full path, and settings for a laptop.

The README in the folder gives each job's messages word for word. Try your script as you go, rehearsal first: .\Backup-SchoolWork.ps1 -Rehearse, then .\Backup-SchoolWork.ps1, then Get-Content .\logs\backup.log.

Check your work

The check uses Pester. If you haven't installed it yet, install it once:

Install-PSResource Pester

Then, from the exercise folder:

Invoke-Pester

At first most tests fail. That's expected: each job you finish turns its tests green. A failing test names the job and says what to look at, for example Expected 1, because robocopy can't copy into a file and ends with 16. Job 7 turns 8 or more into exit 1. The check copies your script into a throwaway folder with made-up school work for every test, and runs it from another folder with -NonInteractive, so your own school-work, backup and logs are never touched. It builds your task and looks at it; nothing is registered on your computer.

If PowerShell says the check can't be loaded because it is not digitally signed, Windows has marked the downloaded files as coming from the internet: from the exercise folder, run Get-ChildItem -Recurse | Unblock-File once, then Invoke-Pester again.

Hints

• The task's folder isn't yours. A task starts in C:\Windows\System32, so every path starts from $PSScriptRoot (Scripts That Run Without You).
• Write-Log prints its line as well as saving it. That's how the transcript gets it too.
• An empty folder. Get-ChildItem on an empty folder gives back nothing, and -not turns nothing into True.
• Read the exit code at once. $LASTEXITCODE changes with the next program that runs, so keep it in a variable right after robocopy (Backups That Work: robocopy).
• Settings have switches. New-ScheduledTaskSettingsSet has one switch for each of the three laptop settings (Scheduled Tasks).

When you're done

Every test is green, and Pester's last line says:

Tests Passed: 17, Failed: 0, Skipped: 0, Inconclusive: 0, NotRun: 0

Rehearse, back up twice, and read the log. | Out-Null hides robocopy's report, which logs\last-run.txt keeps anyway:

.\Backup-SchoolWork.ps1 -Rehearse | Out-Null
.\Backup-SchoolWork.ps1 | Out-Null
.\Backup-SchoolWork.ps1 | Out-Null
Get-Content .\logs\backup.log

2026-11-09 08:27:23 Rehearsal started: C:\Users\Sam\terminal-practice\exercise-powershell-back-up-while-you-sleep\school-work to C:\Users\Sam\terminal-practice\exercise-powershell-back-up-while-you-sleep\backup
2026-11-09 08:27:23 Rehearsal finished (robocopy exit code 1)
2026-11-09 08:27:24 Backup started: C:\Users\Sam\terminal-practice\exercise-powershell-back-up-while-you-sleep\school-work to C:\Users\Sam\terminal-practice\exercise-powershell-back-up-while-you-sleep\backup
2026-11-09 08:27:24 Backup finished (robocopy exit code 1)
2026-11-09 08:27:24 Backup started: C:\Users\Sam\terminal-practice\exercise-powershell-back-up-while-you-sleep\school-work to C:\Users\Sam\terminal-practice\exercise-powershell-back-up-while-you-sleep\backup
2026-11-09 08:27:24 Backup finished (robocopy exit code 0)

The rehearsal copied nothing, the first backup copied the files (1), and the second had nothing to do (0): three good nights. Your dates and times will be your own. The README's last section shows how to register the task on your own PC if you'd like it to run every evening for real; that part changes your computer, so it's yours to choose.

Submit your exercise

The exercise is how you finish this lesson. When your work is done, put it on GitHub in a repo of your own, then submit that repo's address here.

1. On GitHub, click +, then New repository. Name it (for example exercise-powershell-back-up-while-you-sleep), choose Public, and click Create repository. Leave out the README: your folder already has one.

2. In a terminal in your exercise folder (PowerShell works), send your work to your new repo. If you downloaded the ZIP:

   git init -b main
   git add .
   git commit -m "My solution"
   git remote add origin https://github.com/your-name/exercise-powershell-back-up-while-you-sleep.git
   git push -u origin main
   

   If you cloned the starter instead, point your copy at your own repo, then commit and push:

   git remote set-url origin https://github.com/your-name/exercise-powershell-back-up-while-you-sleep.git
   git add .
   git commit -m "My solution"
   git push -u origin main
   

3. Paste your repo's address, such as https://github.com/your-name/exercise-powershell-back-up-while-you-sleep, into Submit your exercise on this page. The site checks that the repo is public and holds your commits, and then the lesson is complete.

Changed something after you submitted? Push it, and submit again: your latest submission is the one that counts.

So what

A backup you'd forget, run by Windows every evening, that writes down what it did and says so when it fails: that's a script working for you while you sleep.

Key terms

• Scheduled Task
• robocopy
• Start-Transcript
• Log File
• Exit Code
• $PSScriptRoot

Related

• Scheduled Tasks
• Scripts That Run Without You
• Backups That Work: `robocopy`