CODEWITHSUNDEEP
powershellargs
Paul
Paul

Reputation: 99

How to prompt for $args when missing

My script:

$computername=$args[0]
if ($args -eq $null) { $computername = Read-Host "enter computer name" }
Get-ADComputer -Id $computername -Properties * | select name,description

If I pass the argument with the script i.e.:

get-ComputerName.ps1 computer01

it works fine. However if I skip the computer I want it to prompt me but instead I'm getting this error:

Get-ADComputer : Cannot validate argument on parameter 'Identity'. The argument
is null. Provide a valid value for the argument, and then try running the
command again.
At U:\get-ADComputer-assigned-user.ps1:9 char:20
+ Get-ADComputer -Id $computername -Properties * | select name,description
+                    ~~~~~~~~~~~~~
    + CategoryInfo          : InvalidData: (:) [Get-ADComputer], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationError,Microsoft.ActiveDirectory.Management.Commands.GetADComputer

I cannot figure out how to make it work.

Upvotes: 3

Views: 5246

Answers (2)

Scooter
Scooter

Reputation: 7061

It appears that $args will always be there, so ($args -eq $null) will always be false. To see if $args is empty you can do

if ($args.Length -eq 0)

Upvotes: 1

Ansgar Wiechers
Ansgar Wiechers

Reputation: 200293

Don't use the automatic variable $args, but define a specific mandatory parameter for the computername:

[CmdletBinding()]
Param(
  [Parameter(Mandatory=$true, Position=0)]
  [string]$ComputerName
)

Get-ADComputer -Id $ComputerName -Properties * | Select-Object Name, Description

That will allow you to run your script like this:

./Get-ComputerName.ps1 -ComputerName computer01

or like this:

./Get-ComputerName.ps1 computer01

If the parameter is missing you'll be prompted for it:

PS C:\> ./Get-ComputerName.ps1

cmdlet test.ps1 at command pipeline position 1
Supply values for the following parameters:
ComputerName: _

If you want the script to throw an error instead of prompting for a missing parameter you could do it like this:

[CmdletBinding()]
Param(
  [Parameter(Mandatory=$false, Position=0)]
  [string]$ComputerName = $(throw 'Parameter missing!')
)

Get-ADComputer -Id $ComputerName -Properties * | Select-Object Name, Description

Check the documentation for further information about parameter handling in PowerShell.

Upvotes: 9

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