Parameters

The following can accept parameters: 1. Cmdlets 2. functions 3. scripts
These make the scripts more flexible

Declare and Use a Parameter

To use parameters we use Param() keyword.

imagine we have a file named script.ps1

Param(
    $Path
)
New-Item $Path
Write-Host "File has been created"

The parameters been to be comma separated.

Use The Parameter

Then inside the PowerShell we can use it as follows.

./script.ps1 -Path "./newfile"

Improve Your Parameters

You should keep the following questions in mind: 1. Is this parameter optional or mandatory? 2. What are the legal and illegal values? 3. Does it accept multiple types of values or single type 4. Can it rely on default values? 5. Can you provide details to the user?

Select an Approach

You can do the following things

If / Else

Param(
   $Path
)

If (-Not $Path -eq '') {
   New-Item $Path
   Write-Host "File created at path $Path"
}

Else {
   Write-Error "Path cannot be empty"
}

Making Parameters Mandatory

You can make a parameter mandatory by using a decorator.

Param(
    [Parameter(Mandatory)]
    $Path
)

If you run the script without providing the value of the parameter, PowerShell would ask you to enter the value for it.

cmdlet script.ps1 at command pipeline position 1 Supply values for the following parameters:
Path:

You can further improve the decorator by providing a HelpMessage.

[Parameter(Mandatory, HelpMessage = "Please provide a valid path")]

Then if you type !?, the HelpMessage will pop up.

cmdlet script.ps1 at command pipeline position 1 Supply values for the following parameters:
(Type !? for Help.) 
Path: !?
Please provide a valid path

Assigning a Type

Param(
    [string]$Path
)

Default Values

Param(
    [string]$Path = "defaut value"
)