Passing Arguments to Encoded Commands

Why Encode PowerShell Code?

Encoding PowerShell code is a great way to run PowerShell code outside the PowerShell environment, i.e. in batch files. Here is some sample code that takes PowerShell code, encodes it, and shows how to run it with a console command:

$command = {
Get-Service | 
    Where-Object Status -eq Running | 
    Out-GridView -Title 'Pick a service that you want to stop' -PassThru | 
    Stop-Service
}

$bytes = [System.Text.Encoding]::Unicode.GetBytes($command)
$encodedCommand = [Convert]::ToBase64String($bytes)
"powershell.exe -noprofile -encodedcommand $encodedCommand" | clip

Running Encoded PowerShell Commands

When you run this code, you find the PowerShell command in the clipboard. It looks similar to this:

When you open a new cmd.exe window, you can paste the code right into it to execute pure PowerShell code. You can run encoded commands anywhere where there is enough space to contain the entire line. Because of length limitations, encoded commands won’t work well inside of shortcut files (.lnk files) and in the Run box inside of the start menu.

And there is another limitation: you can’t pass arguments to encoded commands. Except if you use a cool trick. First, add a param() block to your code, and make the parameter mandatory. Second, pass the arguments via the pipeline in an outer PowerShell.

Here is an example you may want to try:

$command = {
param
(
    [Parameter(Mandatory)]
    [string]
    $FirstName,

    [Parameter(Mandatory)]
    [string]
    $LastName
)
"Hello, your first name is $FirstName and your last name is $lastname!"
}

$bytes = [System.Text.Encoding]::Unicode.GetBytes($command)
$encodedCommand = [Convert]::ToBase64String($bytes)
"powershell.exe -noprofile -command 'Tobias', 'Weltner' | powershell -noprofile -encodedcommand $encodedCommand" | clip

The command looks similar to this:

When you run it, the arguments “Tom” and “Tester” are piped into the PowerShell that executes the encoded command. Since the parameters are mandatory, the piped elements are inserted into the prompts, and processed by the encoded command.

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