Default parameter values in PowerShell

Introduction

Default parameter values let you set a fallback value for a function's input. This means the function still works even if you don't give it all the information.

When you want a function to work with common settings without needing extra input.

When you want to avoid errors if a user forgets to provide a parameter.

When you want to make your script easier to use by providing sensible defaults.

Syntax

PowerShell

function FunctionName {
  param(
    [type]$ParameterName = DefaultValue
  )
  # Function code here
}

You set the default value by using '=' after the parameter name.

If the caller does not provide a value, the default is used automatically.

Examples

This function says hello. If you don't give a name, it uses "Friend".

PowerShell

function Greet {
  param(
    [string]$Name = "Friend"
  )
  Write-Output "Hello, $Name!"
}

Greet
Greet -Name "Alice"

This function adds two numbers. If you don't give numbers, it adds 5 and 10.

PowerShell

function Add-Numbers {
  param(
    [int]$a = 5,
    [int]$b = 10
  )
  return ($a + $b)
}

Add-Numbers
Add-Numbers -a 3 -b 7

Sample Program

This script defines a function that shows a message. If no message is given, it shows "Hello, World!".

PowerShell

function Show-Message {
  param(
    [string]$Message = "Hello, World!"
  )
  Write-Output $Message
}

Show-Message
Show-Message -Message "PowerShell is fun!"

Important Notes

Default values can be any valid PowerShell expression.

You can mix parameters with and without default values, but parameters with defaults should come last.

Using default values makes your functions more flexible and user-friendly.

Summary

Default parameter values provide fallback inputs for functions.

They help avoid errors when parameters are missing.

They make scripts easier to use by setting common defaults.