Agent Skills: PowerShell Master

PowerShell Master

CRITICAL GUIDELINES

Windows File Path Requirements

MANDATORY: Always Use Backslashes on Windows for File Paths

When using Edit or Write tools on Windows, you MUST use backslashes (\) in file paths, NOT forward slashes (/).

Examples:

• WRONG: D:/repos/project/file.tsx
• CORRECT: D:\repos\project\file.tsx

This applies to:

• Edit tool file_path parameter
• Write tool file_path parameter
• All file operations on Windows systems

Documentation Guidelines

NEVER create new documentation files unless explicitly requested by the user.

• Priority: Update existing README.md files rather than creating new documentation
• Repository cleanliness: Keep repository root clean - only README.md unless user requests otherwise
• Style: Documentation should be concise, direct, and professional - avoid AI-generated tone
• User preference: Only create additional .md files when user specifically asks for documentation

Complete PowerShell expertise across all platforms for scripting, automation, CI/CD, and cloud management.

When to Activate

PROACTIVELY activate for ANY PowerShell-related task:

• PowerShell Scripts - Creating, reviewing, optimizing any .ps1 file
• Cmdlets & Modules - Finding, installing, using any PowerShell modules
• Cross-Platform - Windows, Linux, macOS PowerShell tasks
• CI/CD Integration - GitHub Actions, Azure DevOps, Bitbucket Pipelines
• Cloud Automation - Azure (Az), AWS, Microsoft 365 (Microsoft.Graph)
• Module Management - PSGallery search, installation, updates
• Script Debugging - Troubleshooting, performance, security
• Best Practices - Code quality, standards, production-ready scripts

Reference Map

Detailed material lives in references/. Load only what the current task needs.

| Topic | File | When to load | |-------|------|--------------| | Cross-platform patterns (paths, platform detection, encoding, shell detection) | references/cross-platform-patterns.md | Writing scripts that run on Windows + Linux/macOS, or distinguishing PowerShell vs Git Bash | | Module management (PSResourceGet, PSGallery, popular modules) | references/modules-and-gallery.md | Installing/finding modules, Az 14.5.0, Microsoft.Graph 2.32.0, PnP, AWS Tools, offline installs | | CI/CD pipelines (GitHub Actions, Azure DevOps, Bitbucket) | references/cicd-integration.md | Setting up automated PowerShell builds/tests with multi-platform matrices | | Syntax & cmdlet reference (variables, operators, flow, functions, pipeline, error handling, Pester, performance, REST) | references/syntax-reference.md | Authoring scripts, looking up cmdlets, writing Pester tests, performance tuning | | Security (JEA, WDAC, Constrained Language Mode, Script Block Logging, credentials, code signing) | references/security-2025.md | Production security hardening, credential management, audit logging |

PowerShell Overview

PowerShell Versions & Platforms

PowerShell 7+ (Recommended)

• Cross-platform: Windows, Linux, macOS
• Open source, actively developed
• Better performance than PowerShell 5.1
• UTF-8 by default
• Parallel execution support
• Ternary operators, null-coalescing

Windows PowerShell 5.1 (Legacy)

• Windows-only
• Ships with Windows
• UTF-16LE default encoding
• Required for some Windows-specific modules

Installation Locations:

• Windows: C:\Program Files\PowerShell\7\ (PS7) or C:\Windows\System32\WindowsPowerShell\v1.0\ (5.1)
• Linux: /opt/microsoft/powershell/7/ or /usr/bin/pwsh
• macOS: /usr/local/microsoft/powershell/7/ or /usr/local/bin/pwsh

Core Workflow

1. Identify scope — Is this a script, module, automation pipeline, or one-off command? Note target platform(s).
2. Check version & modules — $PSVersionTable.PSVersion, Get-Module -ListAvailable. Confirm PowerShell 7+ unless legacy required.
3. Load the relevant reference(s) from the Reference Map above. Avoid loading material you do not need.
4. Apply the pre-flight checklist (below) before authoring or running production scripts.
5. Validate — Invoke-ScriptAnalyzer for linting, Invoke-Pester for tests, -WhatIf for destructive cmdlets.

Pre-Flight Checklist for Scripts

Before running any PowerShell script, ensure:

1. Platform Detection - Use $IsWindows, $IsLinux, $IsMacOS (see references/cross-platform-patterns.md)
2. Version Check - #Requires -Version 7.0 if needed
3. Module Requirements - #Requires -Modules specified
4. Error Handling - try/catch blocks in place
5. Input Validation - Parameter validation attributes used (see references/syntax-reference.md)
6. No Aliases - Full cmdlet names in scripts
7. Path Handling - Use Join-Path or [IO.Path]::Combine()
8. Encoding Specified - UTF-8 for cross-platform
9. Credentials Secure - Never hardcoded (see references/security-2025.md)
10. Verbose Logging - Write-Verbose for debugging

Quick Decision Guide

Use PowerShell 7+ when:

• Cross-platform compatibility needed
• New projects or scripts
• Performance is important
• Modern language features desired

Use Windows PowerShell 5.1 when:

• Windows-specific modules required (WSUS, GroupPolicy legacy)
• Corporate environments with strict version requirements
• Legacy script compatibility needed

Choose Azure CLI when:

• Simple one-liners needed
• JSON output preferred
• Bash scripting integration

Choose PowerShell Az module when:

• Complex automation required
• Object manipulation needed
• PowerShell scripting expertise available
• Reusable scripts and modules needed

Minimal Script Skeleton

#Requires -Version 7.0

<#
.SYNOPSIS
    Brief description
.DESCRIPTION
    Detailed description
.PARAMETER Name
    Parameter description
.EXAMPLE
    PS> .\script.ps1 -Name "John"
#>

[CmdletBinding()]
param(
    [Parameter(Mandatory=$true)]
    [ValidateNotNullOrEmpty()]
    [string]$Name
)

$ErrorActionPreference = "Stop"
Set-StrictMode -Version Latest

try {
    Write-Verbose "Starting script"
    # ... main logic ...
    Write-Verbose "Script completed successfully"
}
catch {
    Write-Error "Script failed: $_"
    exit 1
}
finally {
    # Cleanup
}

Expand this skeleton using patterns from references/syntax-reference.md (advanced functions, pipeline, error handling) and references/security-2025.md (input validation, credential handling).

Additional Resources

• PowerShell Docs: https://learn.microsoft.com/powershell
• PowerShell Gallery: https://www.powershellgallery.com
• Az Module Docs: https://learn.microsoft.com/powershell/azure
• Microsoft Graph Docs: https://learn.microsoft.com/graph/powershell

For shell detection on Windows (PowerShell vs Git Bash), see the powershell-shell-detection skill.

Remember: ALWAYS research latest PowerShell documentation and module versions before implementing solutions. The PowerShell ecosystem evolves rapidly, and best practices are updated frequently.