MCPInstall

powershell-windows

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

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Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/sickn33/agentic-awesome-skills --skill powershell-windows
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads powershell-windows automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

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. Encoding Compatibility

Prefer portable log markers

Purpose❌ Don't Use✅ Use
Success✅ ✓[OK] [+]
Error❌ ✗ 🔴[!] [X]
Warning⚠️ 🟡[*] [WARN]
Infoℹ️ 🔵[i] [INFO]
Progress⏳[...]

PowerShell supports Unicode. ASCII log markers are a portability choice, not a syntax requirement. For non-ASCII scripts read by Windows PowerShell 5.1, use UTF-8 with BOM; PowerShell 7 uses UTF-8 without BOM by default. Check the consuming tool before choosing file encoding.


3. Null Check Patterns

Always Check Before Access

❌ Wrong✅ Correct
$array.Count -gt 0($null -ne $array) -and (@($array).Count -gt 0)
$text.Lengthif ($null -ne $text) { $text.Length }

4. String Interpolation

Complex Expressions

"Value: $($obj.prop.sub)" is valid subexpression interpolation. Store a complex expression in a variable when that improves readability.

Pattern:

$value = $obj.prop.sub
Write-Output "Value: $value"

5. Error Handling

ErrorActionPreference

ValueUse
StopRequired cmdlet failures must enter catch
ContinueReport a non-terminating error and continue deliberately
SilentlyContinueWhen errors expected

Try/Catch Pattern

  • A return inside try is valid; finally still runs
  • Use finally for cleanup
  • Return after try/catch

6. File Paths

Windows Path Rules

PatternUse
Literal pathC:\Users\User\file.txt
Variable pathJoin-Path $env:USERPROFILE "file.txt"
RelativeJoin-Path $ScriptDir "data"

Rule: Use Join-Path for cross-platform safety.


7. Array Operations

Correct Patterns

OperationSyntax
Empty array$array = @()
Add item$array += $item
ArrayList add`$list.Add($item)

8. JSON Operations

CRITICAL: Depth Parameter

❌ Wrong✅ Correct
ConvertTo-JsonConvertTo-Json -Depth 10

Rule: Always specify -Depth for nested objects.

File Operations

OperationPattern
Read`Get-Content "file.json" -Raw
Write`$data

9. Common Errors

Error MessageCauseFix
"parameter 'or'"Missing parenthesesWrap cmdlets in ()
"Unexpected token"Parsing or quoting errorInspect the reported token and file encoding
"Cannot find property"Null objectCheck null first
"Cannot convert"Type mismatchValidate input and convert to the required type

10. Script Template

# Strict mode
Set-StrictMode -Version Latest
$ErrorActionPreference = "Stop"

# Paths
$ScriptDir = Split-Path -Parent $MyInvocation.MyCommand.Path

# Main
try {
    # Cmdlet logic here; check $LASTEXITCODE after native executables.
    Write-Output "[OK] Done"
    exit 0
}
catch {
    Write-Warning "Error: $_"
    exit 1
}

Remember: Check shell version, encoding, null semantics and native exit codes. try/catch alone does not reliably turn native command failures into exceptions.

References: encoding, quoting.

When to Use

Use when writing or debugging Windows PowerShell or PowerShell 7 scripts, especially command expressions, encoding, paths and error handling.

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.

FAQ

What does the powershell-windows skill do?

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

How do I install powershell-windows?

Run npx skills add https://github.com/sickn33/agentic-awesome-skills --skill powershell-windows in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/powershell-windows/ (personal) or .claude/skills/powershell-windows/ (project).

Which AI agents can use powershell-windows?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is powershell-windows safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains powershell-windows?

It is published by sickn33 in sickn33/agentic-awesome-skills. It has 2,640 recorded installs.

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