Auto-logoff facility in Unix

[Doug Gwyn]

Our version of the Bourne shell will timeout the user if he doesn't
respond to a PS1 prompt within a specified amount of time.  The
environment variable TIMEOUT contains the allowed time in minutes.
Obviously this is not user-proof and in fact setting TIMEOUT=0 will
disable the feature.  The intention is to terminate the shell on an
"abandoned" terminal, like when a fellow goes home for the day and
forgot to log out first.