[K12OSN] Solution? Managing Identical logins

[Robert Arkiletian]

Attention script writers:
I just had an idea. Is it possible to run a script at beginning of login that
would do this

#!/bin/sh

if [$USER != root]
then
   if [who | grep $USER]  #this line needs some help
   then
      #abort login (not sure how to do this)
   fi
fi

basically check to see if the user is already logged in and abort login if true.
I am not familiar with bash script writing. It's on my to learn list. 

At least this way the student who is already logged on with the username will
not get kicked off. Only the second attempt to login with the same username will
fail.

Robert Arkiletian