Preventing PowerShell from Running in the ISE

Once in a great while you will have the need to force your scripts to only run in the console. Mostly likely you have created special formatting commands that only work in the console, but would cause the script to crash in the ISE. It is prudent then to prevent that code from even executing. But how?

Turns out it’s pretty simple. The PowerShell ISE has a built in variable called $psise. Within the ISE you can use this variable to alter various settings in the environment, such as colors, or the position of the code window. When you run from the console however, $psise will be null.

So the solution is simple, just check to see if $psise is null. To make it even easier, I put the code inside a simple function I can import to my various scripts. It checks to see if we’re in the ISE, and if so presents the user with an error and breaks out.

Note, the break will only be effective if you call this from the outermost level script, that is the script you actually run from the console command line. Break will return control to the outer script, which in that case would be nothing.

I admit this is not something you’ll use all that often, if it were you might consider throwing an error as opposed to breaking so you can nest it at any level.

Here is my simple version of the script.

function Prevent-IseExecution ()
{
<#
  .SYNOPSIS
  Prevents a script from executing any further if it's in the ISE
  
  .DESCRIPTION
  The function determines whether it's running in the ISE or a window, 
  if it's in the ISE it breaks, causing further execution of the script to halt. 
#>

  # If we're in the PowerShell ISE, there will be a special variable
  # named $PsIse. If it's null, then we're in the command prompt
  if ($psise -ne $null)
  {
    "You cannot run this script inside the PowerShell ISE. Please execute it from the PowerShell Command Window."
    break # The break will bubble back up to the parent
  }

}

# Stop the user if we're in the ISE
Prevent-IseExecution

# Code will only continue if we're in command prompt
"I must not be in the ISE"