Pipeline

PowerShell · Reference cheat sheet

📋 Overview

The PowerShell pipeline passes objects (not text) between commands. ByValue and ByPropertyName binding decide how properties map to the next cmdlet’s parameters. Use ForEach-Object, Where-Object, and Select-Object as the core filters.

🔧 Core concepts

Begin/Process/End blocks in advanced functions enable true streaming.

💡 Examples

Filter and project:

Get-ChildItem .\logs -File |
  Where-Object { $_.Length -gt 1MB } |
  Select-Object Name, Length, LastWriteTime |
  Sort-Object Length -Descending

ForEach and Tee:

Get-Service |
  Where-Object Status -eq 'Running' |
  ForEach-Object { $_.Name } |
  Tee-Object -Variable names

Property binding:

# Stop-Process binds -Id ByPropertyName
Get-Process notepad -ErrorAction SilentlyContinue |
  Stop-Process -WhatIf

Collect vs stream:

# Parentheses collect all output first
(Get-ChildItem -Recurse).Count

⚠️ Pitfalls

• Wrapping a pipeline in (…) buffers everything—can exhaust memory on large sets.
• Native executables receive text; format may break object pipelines.
• Format-* cmdlets emit formatting objects—don’t pipe them to exporters; use Select-Object first.
• ForEach-Object vs foreach statement: the statement doesn’t stream in the same way.
• Nulls in the pipeline can surprise -eq filters; be explicit.
• Pipeline-bound parameters need correct attributes in custom functions.

🔗 Related

• cmdlets.md
• objects.md
• loops.md
• functions.md
• vs_bash.md