Bash Script Help Needed

[Charlie Hill]

I need to write a script which will kill duplicate login users in Red Hat. 
When the script determines a user has duplicate logins it will kill just the oldest login. The most recent login can not be killed.
 
For operational reasons we can not just limit logins to 1 login only. The duplicate logins are created when RF scanning guns drop off the network. When the gun user logs back on, it creates the duplicate user.
 
I would be very appreciative if the group can provide links / URLs to script repositories. I have limited skills with awk and pearl. 
 
Thanks in advance.
 
Charlie
 
 
Charlie Hill
Systems Administrator
East Penn Mfg Co Inc
1 Deka Road
Lyon Station, Pa. 19536
chill at dekabatteries.com
Phone: 610.682.6361 Ext 2638;   Fax:  610.682.9568 
 
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