How To Create PowerShell Function Mandatory Parameter And Optional Parameter

Overview

PowerShell functions are helpful in saving time when you have repetitive task(s) to be executed. In this guide we will demonstrate, passing function argument(s) value as mandatory and an optional argument. When the value is not given for the mandatory, function will prompt for parameter value.

Applies To

Tested on Windows 10, Windows 2008 R2 and Windows 2012.

Pre-Requisites

Launch PowerShell Command Console or PowerShell ISE.

To run this script, Execution Policy should be set to either of these “AllSigned” or “RemoteSigned” or “Unrestricted”, you can get current execution policy by running the command; “Get-ExecutionPolicy”. Each Policy type and its purpose is shown in the below table.

Policy Type	Purpose
Restricted	No scripts can be run. Windows PowerShell can be used only in interactive mode.
AllSigned	Only scripts signed by a trusted publisher can be run.
RemoteSigned	Downloaded scripts must be signed by a trusted publisher before they can be run.
Unrestricted	No restrictions; all Windows PowerShell scripts can be run.

PowerShell Script – Function

This PowerShell script call function with function’s mandatory argument / parameter value, when the argument value is passed; Passed value will be displayed else an exception will be thrown.

Code Snippet

In this function, one “Parameter” is set to false and “Parameter” is set to true; for argument position 1 is optional and position 2 argument is mandatory.

#
# Simple Function With One Argument Mandatory Value and Second Argument Optional
#
function MandatoryParameter_And_OptionalParameter
{
    param(
        [Parameter(Mandatory=$False, Position=1)]
        [string]$Parameter_Position_One,

        [Parameter(Mandatory=$True, Position=2)]
        [ValidateNotNull()]
        [string]$Parameter_Position_Two
    )    
    Clear-Host
    Write-Host "`n1st Parameter Value that was passed : $Parameter_Position_One`n"
    Write-Host "`n2nd Parameter Value that was passed : $Parameter_Position_Two`n"
    [console]::beep(500,300)
}

Call / Invoke Function - Attribute Name

To invoke / call the function, call the function from the PowerShell CLI or PowerShell ISE. Invoke the function and pass value for the specific attribute.

MandatoryParameter_And_OptionalParameter -Parameter_Position_Two Value_Passed

PowerShell Output #1

After execution of the function and mandatory argument value is passed; argument value is displayed as below;

Invoke Function – Without Passing Argument Value

When the parameter/argument value is not passed; script will ask for input of argument value, as shown below;

MandatoryParameter_And_OptionalParameter

Invoke Function – Passing Argument Value Space

When you intend to set the argument value with multiple words, enclose value with double quotes after invoking the function.

PowerShell Output #2

Slideshare Information

A step by step guide is uploaded to slideshare.

How To Create PowerShell Function Mandatory Parameter and Optional Parameter from VCP Muthukrishna