L6. Files, Error Handling, and Debugging

Filesystem Basics

PowerShell uses providers. The filesystem is one provider, but registry, certificate, and variable drives can appear through similar commands.

Get-Location
Get-ChildItem -Path . -File
New-Item -ItemType Directory -Path .\lab
Copy-Item .\input.txt .\lab\input-copy.txt
Remove-Item .\lab\input-copy.txt -WhatIf

-WhatIf is one of the most important safety habits in PowerShell. Use it before commands that change or delete resources.

Error Types

PowerShell has terminating and non-terminating errors. Many cmdlets report a non-terminating error and continue. To catch those errors in try/catch, use -ErrorAction Stop.

try {
  Get-Item -Path .\missing.txt -ErrorAction Stop
} catch {
  [pscustomobject]@{
    Message = $_.Exception.Message
    Category = $_.CategoryInfo.Category
  }
} finally {
  'Cleanup or final logging goes here'
}

Debugging Habits

• Use Set-StrictMode -Version Latest in scripts while learning.
• Use Write-Verbose for optional diagnostic messages.
• Use $PSStyle.OutputRendering = 'PlainText' when clean logs matter.
• Build scripts in small tested sections.
• Prefer Join-Path over string-concatenating file paths.

Lab

1. Create a directory named ps-lab.
2. Create three text files inside it.
3. Write a script that counts files and catches missing-path errors.
4. Run destructive commands first with -WhatIf.
5. Add Write-Verbose messages and test with -Verbose.