Loops

PowerShell · Reference cheat sheet

📋 Overview

PowerShell provides foreach, for, while, do/while, do/until, and pipeline-oriented ForEach-Object. Prefer streaming pipelines for large collections; use foreach statements when you need break/continue with clearer scopes.

🔧 Core concepts

% is an alias for ForEach-Object; ? for Where-Object. In scripts, prefer full names.

💡 Examples

foreach vs pipeline:

foreach ($f in Get-ChildItem .\logs -File) {
  if ($f.Length -eq 0) { continue }
  $f.FullName
}

Get-ChildItem .\logs -File | ForEach-Object {
  $_.Name.ToUpper()
}

for / while:

for ($i = 0; $i -lt 3; $i++) { $i }

$n = 0
while ($n -lt 3) { $n++; $n }

do/until:

do {
  $r = Get-Random -Maximum 5
} until ($r -eq 0)

Parallel (PS 7+):

1..5 | ForEach-Object -Parallel {
  Start-Sleep -Seconds 1
  $_
} -ThrottleLimit 3

⚠️ Pitfalls

• return inside ForEach-Object acts like continue for the scriptblock in some mental models—actually it exits the scriptblock only; use carefully inside functions.
• Modifying a collection while enumerating it throws—copy first or collect changes.
• foreach ($x in Get-ChildItem -Recurse) can be huge; filter early.
• Pipeline ForEach-Object -Parallel has session/state limits—avoid shared mutable state.
• $foreach automatic variable exists inside foreach statements—don’t overwrite casually.
• Prefer Where-Object before heavy ForEach-Object work.

🔗 Related

• pipeline.md
• conditionals.md
• functions.md
• jobs.md
• objects.md