Powershell Windows

1---2name: powershell-windows3description: "PowerShell Windows patterns. Critical pitfalls, operator syntax, error handling."4risk: unknown5source: community6date_added: "2026-02-27"7---8 9# PowerShell Windows Patterns10 11> Critical patterns and pitfalls for Windows PowerShell.12 13---14 15## 1. Operator Syntax Rules16 17### CRITICAL: Parentheses Required18 19| ❌ Wrong | ✅ Correct |20|----------|-----------|21| `if (Test-Path "a" -or Test-Path "b")` | `if ((Test-Path "a") -or (Test-Path "b"))` |22| `if (Get-Item $x -and $y -eq 5)` | `if ((Get-Item $x) -and ($y -eq 5))` |23 24**Rule:** Each cmdlet call MUST be in parentheses when using logical operators.25 26---27 28## 2. Unicode/Emoji Restriction29 30### CRITICAL: No Unicode in Scripts31 32| Purpose | ❌ Don't Use | ✅ Use |33|---------|-------------|--------|34| Success | ✅ ✓ | [OK] [+] |35| Error | ❌ ✗ 🔴 | [!] [X] |36| Warning | ⚠️ 🟡 | [*] [WARN] |37| Info | ℹ️ 🔵 | [i] [INFO] |38| Progress | ⏳ | [...] |39 40**Rule:** Use ASCII characters only in PowerShell scripts.41 42---43 44## 3. Null Check Patterns45 46### Always Check Before Access47 48| ❌ Wrong | ✅ Correct |49|----------|-----------|50| `$array.Count -gt 0` | `$array -and $array.Count -gt 0` |51| `$text.Length` | `if ($text) { $text.Length }` |52 53---54 55## 4. String Interpolation56 57### Complex Expressions58 59| ❌ Wrong | ✅ Correct |60|----------|-----------|61| `"Value: $($obj.prop.sub)"` | Store in variable first |62 63**Pattern:**64```65$value = $obj.prop.sub66Write-Output "Value: $value"67```68 69---70 71## 5. Error Handling72 73### ErrorActionPreference74 75| Value | Use |76|-------|-----|77| Stop | Development (fail fast) |78| Continue | Production scripts |79| SilentlyContinue | When errors expected |80 81### Try/Catch Pattern82 83- Don't return inside try block84- Use finally for cleanup85- Return after try/catch86 87---88 89## 6. File Paths90 91### Windows Path Rules92 93| Pattern | Use |94|---------|-----|95| Literal path | `C:\Users\User\file.txt` |96| Variable path | `Join-Path $env:USERPROFILE "file.txt"` |97| Relative | `Join-Path $ScriptDir "data"` |98 99**Rule:** Use Join-Path for cross-platform safety.100 101---102 103## 7. Array Operations104 105### Correct Patterns106 107| Operation | Syntax |108|-----------|--------|109| Empty array | `$array = @()` |110| Add item | `$array += $item` |111| ArrayList add | `$list.Add($item) | Out-Null` |112 113---114 115## 8. JSON Operations116 117### CRITICAL: Depth Parameter118 119| ❌ Wrong | ✅ Correct |120|----------|-----------|121| `ConvertTo-Json` | `ConvertTo-Json -Depth 10` |122 123**Rule:** Always specify `-Depth` for nested objects.124 125### File Operations126 127| Operation | Pattern |128|-----------|---------|129| Read | `Get-Content "file.json" -Raw | ConvertFrom-Json` |130| Write | `$data | ConvertTo-Json -Depth 10 | Out-File "file.json" -Encoding UTF8` |131 132---133 134## 9. Common Errors135 136| Error Message | Cause | Fix |137|---------------|-------|-----|138| "parameter 'or'" | Missing parentheses | Wrap cmdlets in () |139| "Unexpected token" | Unicode character | Use ASCII only |140| "Cannot find property" | Null object | Check null first |141| "Cannot convert" | Type mismatch | Use .ToString() |142 143---144 145## 10. Script Template146 147```powershell148# Strict mode149Set-StrictMode -Version Latest150$ErrorActionPreference = "Continue"151 152# Paths153$ScriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path154 155# Main156try {157    # Logic here158    Write-Output "[OK] Done"159    exit 0160}161catch {162    Write-Warning "Error: $_"163    exit 1164}165```166 167---168 169> **Remember:** PowerShell has unique syntax rules. Parentheses, ASCII-only, and null checks are non-negotiable.170 171## When to Use172This skill is applicable to execute the workflow or actions described in the overview.173 174## Limitations175- Use this skill only when the task clearly matches the scope described above.176- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.177- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.