The Object Pipeline

Intermediate ⭐ 80 XP ⏱ 18 min #powershell#pipeline#objects

Filter, select, sort, and transform objects flowing through the PowerShell pipeline.

📖Theory

Because PowerShell pipes objects, you manipulate data by its properties rather than by column position. The core verbs:

Where-Object — filter rows by a condition
Select-Object — pick properties (columns), or -First/-Last N
Sort-Object — order by a property
ForEach-Object — run code per item
Group-Object / Measure-Object — aggregate

Get-Member reveals which properties and methods an object exposes, so you always know what you can filter or select on.

🌍Real-World Example

# Services that are stopped but set to auto-start
Get-Service |
  Where-Object { $_.Status -eq 'Stopped' -and $_.StartType -eq 'Automatic' } |
  Select-Object Name, DisplayName |
  Sort-Object Name

# Top 3 largest files, as JSON
Get-ChildItem -Recurse -File |
  Sort-Object Length -Descending |
  Select-Object -First 3 Name, Length |
  ConvertTo-Json

✍️Hands-On Exercise

List running services, showing only Name and Status.
Find the three largest files in a folder tree.
Group processes by name and count each group.
Export a filtered list to CSV with Export-Csv.

🧾Cheat Sheet▾

Task	Cmdlet
Filter	`Where-Object { $_.Prop -eq x }`
Select columns	`Select-Object A, B`
Top N	`Select-Object -First N`
Sort	`Sort-Object Prop -Descending`
Per-item code	`ForEach-Object { … }`
Group / count	`Group-Object Prop`
To/from JSON	`ConvertTo-Json` / `ConvertFrom-Json`

💬Common Interview Questions▾

What does $_ mean in a PowerShell pipeline?

It’s the current pipeline object inside a script block, e.g. Where-Object { $_.Status -eq 'Running' } filters on each incoming object’s Status property.

How do you select specific properties from objects?

Select-Object Name, Status returns objects with just those properties; add -First N or -Last N to limit the count.

📚Official Documentation

↗ Microsoft — about_Pipelines

📝 My notes on this topic

Auto-saves as you type