Shell script test mini game...

missingdigit.sh

#!/bin/sh

clear
printf "spot the (missing) digit\n" 

# rnd(0..9)
r=$(($RANDOM%10))

# unix EPOCH time in seconds
t=$(($(date +%s)))

for i in {0..9}
do
    if [ "$i" -ne "$r" ]; then
       printf $i
    fi
done

# read an int from keyboard
printf "\n?"
declare -i a
read a

printf "\n"

if [ "$a" -eq "$r" ]; then
   echo "YES"
else 
   echo "NO"
fi

printf "TIME:%is\n" $(($(($(date +%s)))-$t))