HOWTO Automatically logout your UNIX shell
This article is incomplete and was first written in June 2007 for the BeezNest technical website (http://glasnost.beeznest.org/articles/358).
To ensure a shell left open automatically logs out (kicks the user) after a certain idle time, most recent shells implement its autologout.
Just set the right environment variable and you’re done!
The following two expressions are equivalent.
TMOUT (expressed in seconds)
autologout (expressed in minutes)
But maybe what you are looking for is something to lock the console (or terminal) after a certain idle time? In this case, just use vlock.