Passing arguments to Powershell script

Question

I have a script that takes in a max of 3 parameters - username, password and distro.

The script needs to run as administrator since it checks certain things are enabled and can only be done as an admin.

# the command line is:
# linux-docker <username> <password> <distro>
# if no distro is specified then Debian is used.
param ([Parameter(Mandatory)]$username, [Parameter(Mandatory)]$password,  $distro='Debian')

# check if we are in admin mode and switch if we aren't
$currentPrincipal = New-Object Security.Principal.WindowsPrincipal([Security.Principal.WindowsIdentity]::GetCurrent())
if (-Not $currentPrincipal.IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)) {
    if (!([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] "Administrator")) {
        Start-Process powershell.exe "-NoProfile -ExecutionPolicy Bypass -File `"$PSCommandPath`"" -Verb RunAs; 
        Read-Host -Prompt "Failure: Press Enter to exit"
        exit;
    }
}

# ... rest of script

However restarting the script prompts the user for username and password. I would like to pass the arguments to the promoted script.

I first thought that adding $username,$password and $distro to the Start-Process command.

Start-Process powershell.exe "-NoProfile -ExecutionPolicy Bypass -File `"$PSCommandPath`" $username $password $debian" -Verb RunAs;

but that exits with the "Failure" message.

So I looked at -ArgumentList but that dies processing that line:

Start-Process : A positional parameter cannot be found that accepts argument '-NoProfile -ExecutionPolicy Bypass -File "C:\Users\Graham Reeds\Documents\linux-docker.ps1"'.
At C:\Users\Graham Reeds\Documents\linux-docker.ps1:15 char:9
+         Start-Process powershell.exe "-NoProfile -ExecutionPolicy Byp ...
+         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [Start-Process], ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,Microsoft.PowerShell.Commands.StartProcessCommand
 
Failure: Press Enter to exit:

It is probably something simple but I am a noob with Powershell.

Theo · Accepted Answer · 2022-05-05 10:43:31Z

Using the -ArgumentList parameter should work, but for the parameters sent to the script, you need to get their names and values from the BoundParameters hash:

$currentPrincipal = [Security.Principal.WindowsPrincipal] [Security.Principal.WindowsIdentity]::GetCurrent()
$isAdmin = $currentPrincipal.IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)

if (!$isAdmin) {
    $argList = '-NoLogo', '-NoProfile', '-NoExit', '-ExecutionPolicy Bypass', '-File', ('"{0}"' -f $PSCommandPath)
    # Add script arguments
    $argList += $MyInvocation.BoundParameters.GetEnumerator() | ForEach-Object {"-$($_.Key)", "$($_.Value)"}
    try {
        Start-Process PowerShell.exe -WorkingDirectory $pwd.ProviderPath -ArgumentList $argList -Verb Runas -ErrorAction Stop
        # exit the current script
        exit
    }
    catch {
        Write-Warning "Failed to restart script '$PSCommandPath' with runas"
    }
}
# rest of the script

P.S. Personally I like to always type-cast parameters and when possible make it clear in what order the mandatory parameters should be given if not used Named:

param (
    [Parameter(Mandatory = $true, Position = 0)][string] $username, 
    [Parameter(Mandatory = $true, Position = 1)][string] $password,  
    [string] $distro='Debian'
)

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