Keystoke Logger with Backspace Warning

#!/bin/bash

kb="/dev/input/by-path/platform-i8042-serio-0-event-kbd" #keyboard device
logfile="/tmp/bs.log"

#start loggin keystrokes
cat "$kb" | od -i > "$logfile" &

while [ 1 ]
do

    #Get number of times BackSpace has been pressed
    let x="$(tail -n 600 "$logfile"|awk '{print $5}'|grep "^14$"|wc -l)"

    echo "Check keystroke log."

    if [ "$x" -gt "20" ]
    then
        echo "BackSpace has been press to many times in the last 100 keystrokes"
        echo "Are you Drunk?"|wall
        sleep 1m
    fi
    sleep 10

done