Detect if running with administrator privileges under Windows XP

Question

I am trying to work out how to detect whether a user is running with admin rights under Windows XP. This is fairly easy to do in Vista/Win7 thanks to the whoami command. Here's a snippet in Ruby for how to do it under Vista:

Note, the following link now incorporates the solution suggested by muteW

http://gist.github.com/65931

The trouble is, whoami doesn't come with Windows XP and so the above linked method will always return false on WinXP, even if we're running as an administrator.

So, does anyone know of a way to detect whether we're running as an admin under Windows XP using Ruby, command-line tools, batch-files, or even third-party (needs to be open source, really) tools?

Answer 1

This will detect if the user is running in elevated mode (eg a command prompt that was "Run As" Administrator). It relies on the fact that you require admin privileges to read the LOCAL SERVICE account reg key:

reg query "HKU\S-1-5-19"

this will return a non-zero error code if it cannot be read, and zero if it can.
Works from XP up...