PowerShell Windows patterns. Critical pitfalls, operator syntax, error handling.

PowerShell Windows Patterns Critical patterns and pitfalls for Windows PowerShell. 1. Operator Syntax Rules CRITICAL: Parentheses Required ❌ Wrong ✅ Correct if (Test Path "a" or Test Path "b") if ((Test Path "a") or (Test Path "b")) if (Get Item $x and $y eq 5) if ((Get Item $x) and ($y eq 5)) Rule: Each cmdlet call MUST be in parentheses when using logical operators. 2. Unicode/Emoji Restriction CRITICAL: No Unicode in Scripts Purpose ❌ Don't Use ✅ Use Success ✅ ✓ [OK] [+] Error ❌ ✗ 🔴 [!] [X] Warning ⚠️ 🟡 [ ] [WARN] Info ℹ️ 🔵 [i] [INFO] Progress ⏳ [...] Rule: Use ASCII characters only in PowerShell scripts. 3. Null Check Patterns Always Check Before Access ❌ Wrong ✅ Correct $array.Count gt 0 $array and $array.Count gt 0 $text.Length if ($text) { $text.Length } 4. String Interpolation Complex Expressions ❌ Wrong ✅ Correct "Value: $($obj.prop.sub)" Store in variable first Pattern: 5. Error Handling ErrorActionPreference Value Use Stop Development (fail fast) Continue Production scripts SilentlyContinue When errors expected Try/Catch Pattern Don't return inside try block Use finally for cleanup Return after try/catch 6. File Paths Windows Path Rules Pattern Use Literal path C:\Users\User\file.txt Variable path Join Path $env:USERPROFILE "file.txt" Relative Join Path $ScriptDir "data" Rule: Use Join Path for cross platform safety. 7. Array Operations Correct Patterns Operation Syntax Empty array $array = @() Add item $array += $item ArrayList add $list.Add($item) Out Null 8. JSON Operations CRITICAL: Depth Parameter ❌ Wrong ✅ Correct ConvertTo Json ConvertTo Json Depth 10 Rule: Always specify Depth for nested objects. File Operations Operation Pattern Read Get Content "file.json" Raw ConvertFrom Json Write $data ConvertTo Json Depth 10 Out File "file.json" Encoding UTF8 9. Common Errors Error Message Cause Fix "parameter 'or'" Missing parentheses Wrap cmdlets in () "Unexpected token" Unicode character Use ASCII only "Cannot find property" Null object Check null first "Cannot convert" Type mismatch Use .ToString() 10. Script Template Remember: PowerShell has unique syntax rules. Parentheses, ASCII only, and null checks are non negotiable. When to Use This skill is applicable to execute the workflow or actions described in the overview. Limitations Use this skill only when the task clearly matches the scope described above. Do not treat the output as a substitute for environment specific validation, testing, or expert review. Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.

powershell-windows