How to create powershell script I can pass a parameter to

I would like to write a script such that I can pass a variable by the command line to the script. Example would be like below.

.\script.ps1 computername

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Usually in my scripts I would actually enter my variables within the script itself.  A very simple example would be

get-adcomputer computername

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What would I need do to to allow me to pass a parameter to the script through the command line and have it return a value?
LVL 35
Joseph DalyAsked:
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LearnctxEngineerCommented:
Don't worry about cmdlet binding and other advanced functions. Just stick to basic named parameters until you get your head around it all. If you want to pass a parameter to powershell you can do it named, or unnamed. An unnamed parameter is position (taken in the order it is given).

## Top of the script
$ComputerName = $args[0]
$ComputerName

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This would say take:

.\script.ps1 computer1

$ComputerName would be assigned the value computer1. If you were to do:

.\script.ps1 computer1 computer2

You would need to assign both values with $args[0] and $args[1]. $args is an array of all the arguments you provide to a script or function. You can see this is not ideal. It relies on the arguments in the right position always. This is where a named parameter comes in.

## Top of the script
param (
   [string]$ComputerName
)
$ComputerName

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This will let you launch your script with a named parameter like so:

.\script.ps1 -ComputerName Computer1

Casting as a string "[string]" is not required, but its good practice.

If you want to get a bit more advanced, cast it as a string with accepts multiple values.

## Top of the script
param (
   [string[]]$ComputerName
)
Foreach ($Computer in $ComputerName)
{
   $Computer
}

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This will let you launch your script with multiple computer names specified:

.\script.ps1 -ComputerName Computer1, Computer2, Computer3, Computer4

If you want to know more about what Justin Yeung is talking about after understanding parameters better look into "Powershell Advanced Functions" on Google. There are a number of good articles. Few Powershell userse will have a need to used Advanced Functions. I recommend getting a better understanding of named and unnamed parameters for scripts and functions first.
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Justin YeungSenior Systems EngineerCommented:
change your script as a function.

#>
function Verb-Noun #example get-something
{
    [CmdletBinding()]
    [OutputType([int])]
    Param
    (
        # Param1 help description
        [Parameter(Mandatory=$true,
                   ValueFromPipelineByPropertyName=$true,
                   Position=0)]
        [string]$computername

       
    )

{your script}

}
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Joseph DalyAuthor Commented:
Im sure that would work but would you mind explaining what exactly that does and how it does it. Looking at the code I am pretty over my head.
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Justin YeungSenior Systems EngineerCommented:
so what happen is, instead of set the variable within the script, you can specific it as a "required parameter" with (Mandatory=$true).

when you run the script, it will come up and ask you what is $computername will be by typing it in.

powershell can convert script that run to a function or module that can be used with different variable setup.

here is the full powershell 3.0 tutorial from Microsoft Academy, which explain and you can learn from it step by step to powershell.

http://www.microsoftvirtualacademy.com/training-courses/getting-started-with-powershell-3-0-jump-start
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Justin YeungSenior Systems EngineerCommented:
This course actually explain it really well, and I am sure you can learn from it.
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Joseph DalyAuthor Commented:
How would I create a function so that I could pass a .\name.ps1 parameter?
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Justin YeungSenior Systems EngineerCommented:
sorry I don't understand your question.....
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Joseph DalyAuthor Commented:
Thank you the explanation really helped.
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