PowerShell Scripting Fundamentals

Welcome to the core of PowerShell automation! This section covers the essential concepts and syntax required to write powerful and efficient PowerShell scripts. Whether you're automating system administration tasks or developing complex workflows, mastering these fundamentals is key.

What is PowerShell Scripting?

PowerShell scripts are text files (with a .ps1 extension) containing a sequence of PowerShell commands and control flow statements. They allow you to automate repetitive tasks, manage systems at scale, and create custom tools.

Basic Syntax and Commands

PowerShell uses a verb-noun naming convention for its commands, known as cmdlets (pronounced "command-lets").

Get-Process
New-Item -Path "C:\MyFolder" -Name "NewFile.txt"
Stop-Service -Name "Spooler"

Variables

Variables are used to store data. They start with a dollar sign ($).

$userName = "AdminUser"
$computerCount = 10
$isValid = $true

Write-Host "Processing user: $userName"
Write-Host "Number of computers: $computerCount"

Data Types

PowerShell supports various data types, including strings, integers, booleans, arrays, and hashtables.

Arrays: Ordered collections of items.

$servers = "Server01", "Server02", "Server03"
$servers[0] # Accesses the first element ("Server01")

Hashtables: Key-value pairs.

$userConfig = @{
    UserName = "jdoe"
    Department = "IT"
    Active = $true
}
$userConfig["Department"] # Returns "IT"

Control Flow

Control flow statements allow you to dictate the execution path of your script based on conditions.

If/Else Statements

Execute code blocks based on whether a condition is true or false.

$diskSpace = Get-Volume -DriveLetter "C" | Select-Object -ExpandProperty SizeRemaining
$threshold = 10GB

if ($diskSpace -lt $threshold) {
    Write-Warning "Low disk space on C: drive! Available: $([math]::Round($diskSpace / 1GB, 2)) GB"
} else {
    Write-Host "Sufficient disk space on C: drive."
}

Loops

Repeat a block of code multiple times.

For Loop

for ($i = 1; $i -le 5; $i++) {
    Write-Host "Iteration number: $i"
}

ForEach Loop

Iterate over items in a collection.

$files = Get-ChildItem -Path "C:\Logs" -Filter "*.log"
foreach ($file in $files) {
    Write-Host "Processing log file: $($file.Name)"
    # Add more actions here
}

Error Handling

Robust scripts gracefully handle errors.

Tip: Use Try-Catch-Finally blocks for structured error handling.

try {
    $result = Invoke-Command -ComputerName "NonExistentServer" -ScriptBlock { Get-Date }
    Write-Host "Command executed successfully."
} catch {
    Write-Error "An error occurred: $($_.Exception.Message)"
} finally {
    Write-Host "Script execution finished."
}

Comments

Use comments to explain your code. Single-line comments start with #.

# This is a single-line comment
$value = 10 # This comment explains the variable assignment

Block comments are enclosed in <# ... #>.

<#
This is a multi-line comment.
It can span several lines
to provide detailed explanations.
#>

Important: Always strive to write clear, well-commented code for maintainability.

Next Steps

Now that you understand the fundamentals, explore advanced topics like creating functions, building modules, and leveraging PowerShell remoting to manage your infrastructure more effectively.