PowerShell Structures: The Knowledgeable way to Scripting Fundamentals

PowerShell Variables and Scopes

Control structures are an essential aspect of programming that help you define the logic for decision-making, looping, and managing flow. They enable you to assess conditions and variables to determine actions based on specific scenarios. In this post, we’ll explore key PowerShell control structures and provide code examples to get you started.

Conditional Statements

If / ElseIf / Else

This structure evaluates conditions and executes specific actions based on those conditions.

Syntax:

if (<condition>) {
    <action>
} elseif (<condition>) {
    <action>
} else {
    <action>
}

Switch

Use switch to evaluate a variable against multiple values.

Syntax:

switch (<value to test>) {
    <condition 1> { <action 1> }
    <condition 2> { <action 2> }
    default { <default action> }
}

Using Regular Expressions with Switch

The -Regex parameter allows regex matching.

$userInput = Read-Host “Enter a value”

switch -Regex ($userInput) {

    “^[A-Z]” { Write-Host “User input starts with a letter.” }

    “^[0-9]” { Write-Host “User input starts with a number.” }

    default { Write-Host “User input doesn’t start with a letter or number.” }

}

Loops and Iterations

ForEach-Object

Processes each item in a collection. Best used when working with piped objects

$path = $env:TEMP + “baselines”

Get-ChildItem -Path $path | ForEach-Object { Write-Host $_ }

Foreach

Loads all items into a collection before processing.

$path = $env:TEMP + “baselines”
$items = Get-ChildItem -Path $path
foreach ($file in $items) {
    Write-Host $file
}

While Loop

Executes as long as the condition is true.

Syntax:

while (<condition>) {

    <action>

}

Example:

For Loop

Defines an initializer, condition, and iteration

Syntax:

for (<init>; <condition>; <iteration>) {

    <action>

}

Do-While / Do-Until

Executes actions at least once and then checks the condition.

do {
    <action>
} while (<condition>)

Special Statements

Break

Exits a loop immediately.

Example:

Continue

Skips the current iteration and moves to the next one.

Naming Conventions

PowerShell cmdlets and functions follow a Verb-Noun naming convention, such as Get-Help or Stop-Process.

Finding Approved Verbs

Use the Get-Verb cmdlet to see the list of approved verbs.

This guide provides a comprehensive look at PowerShell control structures and how to leverage them for effective scripting. Practice these examples to enhance your understanding and proficiency!