#!/bin/bash

#
# If a workstation is not used for a certain amount of time, take an action
# such as hibernate, suspend or shutdown.
#
# Desktop manager such as Gnome and KDE typically have options to do that,
# but it only works when a use stays logged in. This script only works when
# no user is logged in.
#
# This script checks how many people are logged using who(1) and record
# the result in a file in /var. If the count is zero twice in a row
# (using the value in the file to know what the count was the last time)
# it means nobody has logged in during the interval and action is taken.
#
# Run this script through cron, and set the interval based on what you think
# is reasonable, for example if you run the script every 5 minutes, and
# nobody logs in for 5 to 10 minutes, the machine will hibernate (or suspend,
# or shutdown) automatically.
#
# For example, to shutdown after 5 minutes  with Paul Vixie's cron,
# use a line such as:
#
# 0-59/5 * * * * /usr/local/bin/action_if_nobody.bash hibernate
#
#
# Copyright Yves Dorfsman, Calgary, 2008
#

if [[ $# -ne 1 ]] ; then
  echo -e "\nThis script requires one argument.\n" >&2
  exit 1
fi

case $1 in
                # This script should be run as root, so we use the pm utils
                # from sbin
  hibernate)    ACTION="/usr/sbin/pm-hibernate" ;;
  suspend)      ACTION="/usr/sbin/pm-suspend"   ;;
  shutdown)     ACTION="/sbin/shutdown -hy now" ;;
  *)            echo -e "\nThe argument can only be hibernate, suspend or shutdown.\n" >&2
                exit 1
esac


# We use /var/run to prevent non-root users to touch the file
COUNTFILE=/var/run/who_count

WHO=/usr/bin/who


ACTION_NOW=0
WHO_COUNT_NOW=$($WHO |wc -l)

# If there is no file, we don't know the last count, so we skip
if [[ -f $COUNTFILE ]] ; then
  WHO_COUNT_LAST=$(head -1 $COUNTFILE)

  # Was the content of the file valid ?
  echo $WHO_COUNT_LAST |egrep '^([0-9])+$' >/dev/null 2>&1
  if [[ $? -eq 0 ]] ; then
    echo who count last $WHO_COUNT_LAST
    echo who count now $WHO_COUNT_NOW
    let TOTAL=WHO_COUNT_LAST+WHO_COUNT_NOW
    echo totalw $TOTAL

    if [[ TOTAL -eq 0 ]] ; then
      ACTION_NOW=1
    fi

  fi
  
fi


echo $WHO_COUNT_NOW > $COUNTFILE
(( $ACTION_NOW )) && $ACTION