#!/bin/sh 

# turn the system's monitor on or off, manually or via timeout.  think of
#  it as the ultimate screen-saver.  this works on linux.


prog=`basename $0`

# invoked as "mon", turn the monitor on.  i have a user named "mon" on my
# system, whose .profile runs "monit on".  i can sit down at a blank screen
# and type "mon", and if i'm either at a login prompt or a shell prompt,
# the right thing will happen.  and the 'mo', and 'n' commands are pretty
# benign in vi, so i don't trash things in editor sessions if that's what
# i happen to hit, either.  and some people think modeless editors are better.
# hah!

# invoke from cron periodically

if [ "$prog" = mon ]
then
	action=on		#invoked as "mon"
elif [ "$prog" = moff ]
then
	action=off		#invoked as "moff"
else
    action=$1			#invoked as "monit on/off", or "monit timeout"
fi

case $action in
	on) heyu turn monitor on
	;;
	off) heyu turn monitor off
	;;
	timeout)
		# get a list of all users on console devices (tty[0-9])
		w -hs > /tmp/monit$$
		users=`egrep 'tty[0-9]' /tmp/monit$$ | wc -l`

		# get a list of those users that have been on for an 
		# hour or more.  parse the output of the 'w' command.
		idleusers=`egrep \
		    'tty[0-9].*[1-9][0-9]*:[0-9]|tty[0-9].*[1-9][0-9]*days' \
	 		/tmp/monit$$ | wc -l`
		
		# if all of the users are idle, turn it off
		# this also picks up the case where there are no logged-in
		# users at all.
		if [ "$idleusers" = "$users" ]
		then
			heyu turn monitor off
		fi
		rm -f /tmp/monit$$
	;;
	*)
		echo "usage: $prog on|off|timeout" >&2
		echo "	to control the console monitor" >&2
		echo "	(timeout will shut it off after an idle hour)" >&2
		exit 1
	;;
esac

exit