Raspberry Pi: CPU usage monitoring using GPIO

#!/bin/bash
# script created by chteuchteu
# original article here:
# http://www.chteuchteu.com/2012/11/05/raspberry-pi-cpu-usage-monitoring-using-gpio
# www.chteuchteu.com

# Has to be done once at the begging of the script
echo "4" > /sys/class/gpio/export 2> /dev/null
echo "17" > /sys/class/gpio/export 2> /dev/null
echo "18" > /sys/class/gpio/export 2> /dev/null
echo "25" > /sys/class/gpio/export 2> /dev/null
echo "22" > /sys/class/gpio/export 2> /dev/null
echo "23" > /sys/class/gpio/export 2> /dev/null
echo "24" > /sys/class/gpio/export 2> /dev/null
echo "out" > /sys/class/gpio/gpio4/direction
echo "out" > /sys/class/gpio/gpio17/direction
echo "out" > /sys/class/gpio/gpio18/direction
echo "out" > /sys/class/gpio/gpio25/direction
echo "out" > /sys/class/gpio/gpio22/direction
echo "out" > /sys/class/gpio/gpio23/direction
echo "out" > /sys/class/gpio/gpio24/direction

        #################
        #   1   |   18  #
        #   2   |   4   #
        #   3   |   25  #
        #   4   |   17  #
        #   5   |   22  #
        #   6   |   23  #
        #   7   |   24  #
        #################


#################################################
#                   FUNCTIONS                   #
#################################################

number=0
gpio=0

function ON
{
    # Allow you to turn on the del (the number of the del is contained in "number")
    # number <-> pin is done at the begining of the function

    if  [ ${number} -gt 0 ] ; then
        if [ ${number} == 1 ] ; then
            gpio=18
        elif [ ${number} == 2 ] ; then
            gpio=4
        elif [ ${number} == 3 ] ; then
            gpio=25
        elif [ ${number} == 4 ] ; then
            gpio=17
        elif [ ${number} == 5 ] ; then
            gpio=22
        elif [ ${number} == 6 ] ; then
            gpio=23
        elif [ ${number} == 7 ] ; then
            gpio=24
        fi

        echo "1" > /sys/class/gpio/gpio$gpio/value
        number=0
        gpio=0
    fi
}
function OFF
{
    # Allow you to turn off the del (the number of the del is contained in "number")
    # number <-> pin is done at the begining of the function

    if  [ ${number} -gt 0 ] ; then
        if [ ${number} == 1 ] ; then
            gpio=18
        elif [ ${number} == 2 ] ; then
            gpio=4
        elif [ ${number} == 3 ] ; then
            gpio=25
        elif [ ${number} == 4 ] ; then
            gpio=17
        elif [ ${number} == 5 ] ; then
            gpio=22
        elif [ ${number} == 6 ] ; then
            gpio=23
        elif [ ${number} == 7 ] ; then
            gpio=24
        fi

        echo "0" > /sys/class/gpio/gpio$gpio/value
        number=0
        gpio=0
    fi
}

function allON
{
    # Turns ON all the dels
    number=1 ; ON
    number=2 ; ON
    number=3 ; ON
    number=4 ; ON
    number=5 ; ON
    number=6 ; ON
    number=7 ; ON
}
function allOFF
{
    # Turns OFF all the dels
    number=1 ; OFF
    number=2 ; OFF
    number=3 ; OFF
    number=4 ; OFF
    number=5 ; OFF
    number=6 ; OFF
    number=7 ; OFF
}
function flash
{
    i=0
    while [ ${i} -lt 10 ] ; do
        allON
        sleep 0.08
        allOFF
        sleep 0.08

        i=$(( i + 1))
    done
}

#################################################
#                   MAIN CODE                   #
#################################################

number=1 ; ON
sleep 0.3
number=2 ; ON
sleep 0.3
number=3 ; ON
sleep 0.3
number=4 ; ON
sleep 0.3
number=5 ; ON
sleep 0.3
number=6 ; ON
sleep 0.3
number=7 ; ON
sleep 1

allOFF


i=0
while [ ${i} -lt 200 ] ; do
    # Processing the current CPU usage
    idle=`vmstat 2 3 | tail -n1 | sed "s/\ \ */\ /g" | cut -d' ' -f 16`
    cpu=$(( 100 - idle ))

    echo "######## $i / 200 ########"
    echo "CPU usage: $cpu        (idle: $idle)"

    # Switching the dels on or off depending of the "cpu" value
    allOFF
    if [ ${cpu} -lt 15 ] ; then
        number=1    ; ON
        echo " 1 0 0 0 0 0 0 "

    elif [ ${cpu} -lt 30 ] ; then
        number=1    ; ON
        number=2    ; ON
        echo " 1 1 0 0 0 0 0 "

    elif [ ${cpu} -lt 45 ] ; then
        number=1    ; ON
        number=2    ; ON
        number=3    ; ON
        echo " 1 1 1 0 0 0 0 "

    elif [ ${cpu} -lt 60 ] ; then
        number=1    ; ON
        number=2    ; ON
        number=3    ; ON
        number=4    ; ON
        echo " 1 1 1 1 0 0 0 "

    elif [ ${cpu} -lt 75 ] ; then
        number=1    ; ON
        number=2    ; ON
        number=3    ; ON
        number=4    ; ON
        number=5    ; ON
        echo " 1 1 1 1 1 0 0 "

    elif [ ${cpu} -lt 90 ] ; then
        number=1    ; ON
        number=2    ; ON
        number=3    ; ON
        number=4    ; ON
        number=5    ; ON
        number=6    ; ON
        echo " 1 1 1 1 1 1 0 "

    else
        number=1    ; ON
        number=2    ; ON
        number=3    ; ON
        number=4    ; ON
        number=5    ; ON
        number=6    ; ON
        number=7    ; ON
        echo " 1 1 1 1 1 1 1 "
    fi

    echo

    i=$(( i + 1))
done

allOFF

exit 0