Find Primes in Bash

# straight outta fub

printf "Starting Point [SPACE] Ending Point: "
read -r starting ending

IsPrime=1

while [ $starting -le $ending ]
do
    iteration=2
    IsPrime=1

    while [ $iteration -lt $starting ]
    do
        if [ `expr $starting % $iteration` -eq 0 ]
        then
            IsPrime=0
            break
        fi
            iteration=`expr $iteration + 1`
    done

    if [ $IsPrime -eq 1 ]
    then
        printf "$starting "
    fi
        starting=`expr $starting + 1`
done
echo