powershell

PowerShell

A task-based command-line shell and scripting language built on .NET.

When to Use

• Windows Enterprise & Active Directory Automation: Managing Windows Server, Azure Active Directory, Hyper-V, and Exchange estates.
• Cross-Platform DevOps Automation (PS 7+): Writing cross-platform administration scripts executing identically on Windows, Linux, and macOS.
• Azure Infrastructure Orchestration (Az Module): Automating cloud resource deployment, subscriptions, and security compliance policies.
• Object-Oriented Pipeline Scripting: Passing structured .NET objects between commands rather than raw unstructured text streams.

Quick Start

$name = "World"
Write-Host "Hello, $name!"

$processes = Get-Process | Where-Object { $_.CPU -gt 10 } foreach ($p in $processes) { Write-Output $p.Name }

## Core Concepts

### Object-Oriented Pipeline Architecture

Commands pass strongly-typed .NET objects rather than plain text; downstream commands access properties directly:

```powershell
# Passes rich Process objects through the pipeline
Get-Process |
  Where-Object WorkingSet64 -GT 500MB |
  Sort-Object WorkingSet64 -Descending |
  Select-Object -First 5 -Property Name, Id, @{Name="RAM_MB"; Expression={$_.WorkingSet64 / 1MB}}

Advanced Parameter Validation & Cmdlet Binding

Enforces parameter types, mandatory attributes, and validation rules:

function Invoke-Deployment {
    [CmdletBinding(SupportsShouldProcess)]
    param(
        [Parameter(Mandatory = $true)]
        [ValidateSet("Staging", "Production")]
        [string]$Environment,

        [Parameter(Mandatory = $true)]
        [ValidatePattern('^v\d+\.\d+\.\d+$')]
        [string]$Version
    )

    if ($PSCmdlet.ShouldProcess($Environment, "Deploying release $Version")) {
        Write-Host "Deploying $Version to $Environment..." -ForegroundColor Green
    }
}

Error Action Preferences and Try/Catch

Handles terminating and non-terminating errors cleanly:

$ErrorActionPreference = "Stop" # Treat all errors as terminating

try {
    Invoke-RestMethod -Uri "https://api.internal.corp/status" -Method GET -TimeoutSec 5
} catch [System.Net.WebException] {
    Write-Warning "Network connection failed: $($_.Exception.Message)"
} catch {
    Write-Error "Unexpected fatal error: $_"
}

Common Patterns

Advanced Pipeline Function with ShouldProcess Support

Problem: Automating destructive infrastructure changes without dry-run safety mechanisms.

Solution: Build advanced functions supporting -WhatIf and pipeline input:

function Remove-StaleLogs {
    [CmdletBinding(SupportsShouldProcess = $true)]
    param(
        [Parameter(Mandatory = $true, ValueFromPipelineByPropertyName = $true)]
        [string]$Path,
        [int]$DaysOld = 30
    )
    process {
        $cutoff = (Get-Date).AddDays(-$DaysOld)
        Get-ChildItem -Path $Path -Filter *.log | Where-Object { $_.LastWriteTime -lt $cutoff } | ForEach-Object {
            if ($PSCmdlet.ShouldProcess($_.FullName, "Delete stale log")) {
                Remove-Item $_.FullName -Force
            }
        }
    }
}

Best Practices

Do:

• Follow Standard Approved Verb-Noun Naming: Use approved verbs (Get-, Set-, New-, Remove-, Invoke-).
• Use PowerShell 7+ (pwsh): Standardize on cross-platform PowerShell 7+; avoid legacy Windows PowerShell 5.1.
• Add [CmdletBinding()] to Custom Functions: Gain automatic support for -Verbose, -Debug, and -ErrorAction.
• Use PSScriptAnalyzer in CI: Run automated static analysis to catch security flaws and code quality issues.

Don't:

• Use command aliases in production scripts: Avoid ls, cat, curl, and select; use full cmdlet names (Get-ChildItem).
• Parse text output with regex when objects exist: Access object properties directly ($proc.Id) rather than parsing text.
• Store plaintext passwords: Use PSCredential with SecretManagement or Azure Key Vault.

Troubleshooting

Error	Cause	Solution
execution of scripts is disabled on this system	Execution policy restricts running unsigned PowerShell scripts.	Run Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy RemoteSigned.
The term '...' is not recognized as the name of a cmdlet	Module not installed, missing in $env:PSModulePath, or typo.	Install module with Install-Module -Name <Name>.
Cannot bind argument to parameter because it is null	Parameter defined with [Parameter(Mandatory)] received null input.	Verify pipeline output or provide default parameter value.

References

• Microsoft PowerShell Docs