Functions and Parameters

Functions let you package reusable blocks of code under a name you can call anytime. In PowerShell, you define a function with the function keyword and should follow the Verb-Noun naming convention — just like built-in cmdlets.

Defining a Simple Function

function Get-Greeting {
    "Hello, World!"
}

Get-Greeting   # outputs: Hello, World!

Adding Parameters with param()

Use a param() block inside the function to declare parameters. You can specify types and default values:

function Get-Greeting {
    param(
        [string]$Name = "World"
    )
    "Hello, $Name!"
}

Get-Greeting -Name "Alice"   # Hello, Alice!
Get-Greeting                 # Hello, World!

Mandatory Parameters

Mark a parameter as required using the [Parameter(Mandatory)] attribute:

function New-UserReport {
    param(
        [Parameter(Mandatory)]
        [string]$Username,

        [int]$Year = (Get-Date).Year
    )
    "Report for $Username - Year: $Year"
}

If the caller omits -Username, PowerShell will prompt for it automatically.

Parameter Types

Adding a type constraint like [string], [int], or [bool] tells PowerShell to validate and convert input:

function Get-Square {
    param([int]$Number)
    $Number * $Number
}

Get-Square -Number 7   # 49

Return Values

PowerShell functions return any output that is not captured or redirected. You can also use the return keyword, which outputs a value and exits the function:

function Test-EvenNumber {
    param([int]$Number)
    if ($Number % 2 -eq 0) { return $true }
    return $false
}