PowerShell Windows patterns. Critical pitfalls, operator syntax, error handling.
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Critical patterns and pitfalls for Windows PowerShell.
| ❌ 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.
| Purpose |
|---|
| ❌ Don't Use |
|---|
| ✅ Use |
|---|
| Success | ✅ ✓ | [OK] [+] |
| Error | ❌ ✗ 🔴 | [!] [X] |
| Warning | ⚠️ 🟡 | [*] [WARN] |
| Info | ℹ️ 🔵 | [i] [INFO] |
| Progress | ⏳ | [...] |
Rule: Use ASCII characters only in PowerShell scripts.
| ❌ Wrong | ✅ Correct |
|---|---|
$array.Count -gt 0 | $array -and $array.Count -gt 0 |
$text.Length | if ($text) { $text.Length } |
| ❌ Wrong | ✅ Correct |
|---|---|
"Value: $($obj.prop.sub)" | Store in variable first |
Pattern:
$value = $obj.prop.sub
Write-Output "Value: $value"
| Value | Use |
|---|---|
| Stop | Development (fail fast) |
| Continue | Production scripts |
| SilentlyContinue | When errors expected |
| 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.
| Operation | Syntax |
|---|---|
| Empty array | $array = @() |
| Add item | $array += $item |
| ArrayList add | `$list.Add($item) |
| ❌ Wrong | ✅ Correct |
|---|---|
ConvertTo-Json | ConvertTo-Json -Depth 10 |
Rule: Always specify -Depth for nested objects.
| Operation | Pattern |
|---|---|
| Read | `Get-Content "file.json" -Raw |
| Write | `$data |
| 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() |
# Strict mode
Set-StrictMode -Version Latest
$ErrorActionPreference = "Continue"
# Paths
$ScriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path
# Main
try {
# Logic here
Write-Output "[OK] Done"
exit 0
}
catch {
Write-Warning "Error: $_"
exit 1
}
Remember: PowerShell has unique syntax rules. Parentheses, ASCII-only, and null checks are non-negotiable.
Create or update AgentSkills. Use when designing, structuring, or packaging skills with scripts, references, and assets.
Create or update AgentSkills. Use when designing, structuring, or packaging skills with scripts, references, and assets.
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Create or update AgentSkills. Use when designing, structuring, or packaging skills with scripts, references, and assets.
Create or update AgentSkills. Use when designing, structuring, or packaging skills with scripts, references, and assets.
Set up and use 1Password CLI (op). Use when installing the CLI, enabling desktop app integration, signing in (single or multi-account), or reading/injecting/running secrets via op.
CLI to manage emails via IMAP/SMTP. Use `himalaya` to list, read, write, reply, forward, search, and organize emails from the terminal. Supports multiple accounts and message composition with MML (MIME Meta Language).