#!/usr/bin/env bash

USAGE="$(basename $0) <options> \n
\n
\t      Print all prime numbers between the two specified numbers. \n
\n
\t      Options \n
\n
\t\t            [-h|--help]\t\t\t                               This message gets printed only. \n
\t\t            [-n|--min] <the start number>\t The start number, inclusive. \n
\t\t            [-m|--max] <the end number>\t   The end number, inclusive. \n
"

args=`getopt -o "hn:m:" -l "help,min,max" -- "$@"`
eval set -- "$args"
while true; do
  case "$1" in
                -h | --help)    echo -e ${USAGE};       exit;;
                -n | --min)             shift; min="$1";        shift;;
                -m | --max)             shift; max="$1";        shift;;
                --) shift; break;;
                *) echo "Internal error!"; exit 1;;
  esac
done

if [[ ${min}%2 -eq 0 ]]; then
        min=$((${min} + 1))
fi

total=0
first_prime=2
second_prime=3
for ((i=${min}; i<=${max};)); do
        sqrt_of_i=$(echo "sqrt($i)" | bc -l)
        sqrt_of_i=${sqrt_of_i%.*}

        is_prime=true
        for ((j=${second_prime}; j<=${sqrt_of_i};)); do
                if [[ ${i}%$j -eq 0 && $i -ne $j ]]; then
                        #echo prime=false i=$i j=$j
                        is_prime=false
                        break
                fi

                j=$(($j + ${first_prime}))
        done
        if [[ $is_prime == true ]]; then
                #echo is_prime=$is_prime
                total=$(($total+1))
                #echo $i
        fi

        i=$(($i + ${first_prime}))
done

echo "Total primes: $total"