Powershell Patterns

PowerShell Patterns for Development

Critical Pitfalls

Templates with {{ }} — NEVER use Set-Content or heredocs

PowerShell interprets {{ }} as variable interpolation. Use the agent's create_file tool for any file containing {{ }}, ${{}}, or Angular syntax.

# ❌ NEVER:
Set-Content file.html @"<div>{{ title }}</div>"@

# ✅ Always: agent create_file tool
# Editing existing files: replace_string_in_file
# Commands WITHOUT {{ }}: Set-Content with single quotes works fine

nvm-windows

• nvm install X.Y.Z does NOT auto-activate → nvm use X.Y.Z is mandatory
• nvm list shows installed versions, * = active
• Global packages (@angular/cli) are NOT migrated between versions
• Requires Admin shell — run PowerShell as Administrator
• @angular/cli@22 → Node ^22.22.3 || ^24.15.0 || >=26.0.0

Chaining — NEVER &&

&& is not valid in PowerShell 5.1:

npm install; npm run build   # OK
npm install                  # Better: separate commands
npm run build

Execution Policy

Windows 11/10 default to Restricted — .ps1 scripts won't execute.

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned              # Requires admin
Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser  # Without admin

Best Practices

1. Native cmdlets not aliases: Get-ChildItem not ls, Select-String not findstr
2. Quote paths: "C:\Path With Spaces\file.txt"
3. Select-Object -First N to limit output
4. 2>$null to suppress stderr
5. Test-Path before reading/writing
6. NEVER Start-Sleep — the agent is notified when async commands finish
7. Remove-Item -Force to delete; Push-Location/Pop-Location to navigate

File Operations Decision Table