Making the LED on router flash with traffic. http://sorz.org/flashled/

flash-led.sh

#!/bin/sh
#set -x
export PATH="/bin:/sbin:/usr/sbin:/usr/bin"

IFNAME="eth0"
FULLSPEED=1200  # KiB/s
LED='/sys/class/leds/tp-link:blue:system/brightness'

while [ True ]
do

# Get traffic data:
str=$(ifconfig $IFNAME | grep 'RX bytes')
str=${str#*'RX bytes:'}
str=${str%' ('*}
str=${str%' ('*}
now=$((str/1024))

speed=$((now-last))
if [ "$speed" -gt "$FULLSPEED" ] ; then
        speed="$FULLSPEED"
fi
last="$now"

# Flash LED:
ratio=`echo "scale=3;$speed/$FULLSPEED*1000"|bc`
ontime=${ratio%'.'*}
offtime=$((1000-ontime))
#echo "$ontime"

if [ "$ontime" -gt "0" ] ; then
        echo 255 > "$LED"
        msleep "$ontime"
fi

if [ "$offtime" -gt "0" ] ; then
        echo 0 > "$LED"
        msleep "$offtime"
fi

#sleep 10
done