PowerShell Scripting Fundamentals

Published: 2023-10-27 Author: Microsoft Docs Team Version: 7.3

PowerShell scripting is the art of automating tasks and managing systems through the creation and execution of PowerShell scripts. These scripts are essentially text files containing a series of PowerShell commands and logic that can be run to perform complex operations, from simple file manipulation to sophisticated system administration.

Why Script with PowerShell?

PowerShell offers numerous advantages for scripting:

Object-Oriented Pipeline: Unlike traditional text-based shells, PowerShell passes objects between cmdlets. This means data retains its structure and properties, making it easier to filter, sort, and manipulate.
Rich Command Set: PowerShell provides a vast collection of built-in cmdlets for managing Windows and various Microsoft products.
Extensibility: You can create your own cmdlets, functions, and modules to extend PowerShell's capabilities.
Cross-Platform: PowerShell Core (v6+) is cross-platform, allowing you to script on Windows, macOS, and Linux.
Integration: Seamless integration with .NET Framework and COM objects.

Basic Script Structure

A PowerShell script is typically saved with a .ps1 file extension. Here's a simple example:

# This is a simple PowerShell script

$greeting = "Hello"
$name = Read-Host "Enter your name"

Write-Host "$greeting, $name!"

# Get the current date and time
$currentTime = Get-Date
Write-Host "The current date and time is: $currentTime"

Key Scripting Concepts

Variables

Variables in PowerShell start with a dollar sign ($) and are used to store data. You can assign values using the assignment operator (=).

$computerName = "SERVER01"
$portNumber = 80
$isEnabled = $true

Cmdlets

Cmdlets are the fundamental commands in PowerShell. They follow a Verb-Noun naming convention, such as Get-Process, Stop-Service, or New-Item.

# Get running processes on the local machine
Get-Process

# Start the 'Spooler' service
Start-Service -Name Spooler

# Create a new directory
New-Item -Path "C:\Scripts\MyNewFolder" -ItemType Directory

Control Flow

PowerShell supports standard control flow structures like if/else statements, for loops, foreach loops, and while loops.

If/Else Statements

$userRole = "Administrator"

if ($userRole -eq "Administrator") {
    Write-Host "Full access granted."
} else {
    Write-Host "Limited access."
}

ForEach Loops

$files = Get-ChildItem "C:\Logs"

foreach ($file in $files) {
    Write-Host "Processing file: $($file.Name)"
    # You can add more operations here, like copying or deleting
}

Functions

Functions allow you to group code into reusable blocks. They improve script organization and readability.

function Get-SystemInfo {
    param(
        [string]$ComputerName = $env:COMPUTERNAME
    )

    Write-Host "Gathering information for: $ComputerName"
    Get-ComputerInfo -ComputerName $ComputerName
}

# Call the function
Get-SystemInfo -ComputerName "ANOTHERPC"

Important Note on Execution Policy

By default, PowerShell's execution policy may prevent scripts from running. You might need to adjust it using Set-ExecutionPolicy (e.g., Set-ExecutionPolicy RemoteSigned). Always understand the security implications before changing the execution policy.

Advanced Scripting Topics

As you become more comfortable, explore:

Error Handling: Using try/catch/finally blocks.
Modules: Packaging and distributing reusable code.
Remoting: Running commands and scripts on remote computers.
Desired State Configuration (DSC): For declarative system management.
Web Requests: Using Invoke-RestMethod and Invoke-WebRequest to interact with web services.

Tip: Use the PowerShell Integrated Scripting Environment (ISE) or VS Code

These tools provide syntax highlighting, IntelliSense, debugging capabilities, and more, greatly enhancing your scripting experience.

Mastering PowerShell scripting is a valuable skill for any IT professional. Start with simple tasks, gradually build complexity, and leverage the extensive documentation and community resources available.