Introduction to PowerShell

PowerShell is a powerful command-line shell and scripting language designed for automation and configuration management. Built on .NET, it provides deep system integration, making it a valuable tool for administrators and developers.

Why Use PowerShell?

• Automates repetitive tasks
• Manages system configurations
• Works with various data formats (JSON, XML, CSV)
• Supports remote administration
• Extensible via modules and scripts

Getting Started

Installation

PowerShell comes pre-installed on Windows, but newer versions (PowerShell Core) are cross-platform and can be installed on macOS and Linux.

Check PowerShell Version

$PSVersionTable.PSVersion

Install PowerShell Core

• Windows: Download from Microsoft Store (opens in a new tab)
• Linux/macOS: Use a package manager (e.g., brew install powershell for macOS)

Running PowerShell

• Windows: Open PowerShell or pwsh for PowerShell Core.
• macOS/Linux: Run pwsh in a terminal.

Commands and Syntax

Cmdlets

PowerShell commands are called cmdlets and follow a Verb-Noun format.

Get-Process   # Retrieves running processes
Stop-Service  # Stops a service

Finding Commands

Get-Command -Noun Process
Get-Help Get-Process -Full

Variables and Data Types

Declaring Variables

$Name = "PowerShell"
$Number = 10
$IsAdmin = $true

Data Types

[String]$Text = "Hello"
[Int]$Age = 30
[Array]$Items = @(1,2,3)

Operators

Arithmetic Operators

$Sum = 5 + 10
$Multiply = 4 * 3

Comparison Operators

$Result = 5 -eq 5    # True
$Check = 10 -gt 5    # True

Loops and Conditional Statements

If-Else

if ($Age -ge 18) {
    Write-Output "Adult"
} else {
    Write-Output "Minor"
}

Loops

# For Loop
for ($i=0; $i -lt 5; $i++) { Write-Output $i }
 
# While Loop
$counter = 1
while ($counter -le 3) {
    Write-Output $counter
    $counter++
}

Functions and Scripts

Creating Functions

function Greet {
    param ($Name)
    Write-Output "Hello, $Name!"
}
Greet -Name "User"

Running Scripts

Save as script.ps1, then execute:

.\script.ps1

Modules and Packages

Importing Modules

Import-Module ActiveDirectory

Installing Modules

Install-Module -Name PowerShellGet

File System Operations

Working with Files

New-Item -Path "test.txt" -ItemType File
Get-Content "test.txt"

Working with Directories

New-Item -Path "C:\Temp" -ItemType Directory
Remove-Item -Path "C:\Temp" -Recurse

Working with JSON, XML, and CSV

JSON

$Data = Get-Content "data.json" | ConvertFrom-Json
$Data | ConvertTo-Json | Out-File "output.json"

XML

[xml]$xmlData = Get-Content "data.xml"
$xmlData.DocumentElement.ChildNodes

CSV

$csv = Import-Csv "data.csv"
$csv | Export-Csv "output.csv" -NoTypeInformation

Registry and WMI

Query Registry

Get-ItemProperty -Path "HKLM:\Software\Microsoft\Windows\CurrentVersion"

Query WMI

Get-WmiObject Win32_OperatingSystem

Remote Execution

Running Remote Commands

Invoke-Command -ComputerName "Server01" -ScriptBlock { Get-Service }

Entering Remote Sessions

Enter-PSSession -ComputerName "Server01"

Error Handling and Debugging

Try-Catch Blocks

try {
    Get-Item "C:\NonExistentFile.txt"
} catch {
    Write-Output "Error: $_"
}

Debugging Scripts

Set-PSDebug -Trace 1

Best Practices

General Guidelines

• Use meaningful variable names
• Follow Verb-Noun naming convention for functions
• Use comments to improve readability
• Avoid hardcoding values; use parameters instead

Security Practices

• Avoid running scripts from untrusted sources
• Use Set-ExecutionPolicy to control script execution
• Regularly update PowerShell modules

This guide provides a solid foundation in PowerShell. Keep exploring and practicing!