A is_prime function in bash script using trail division, thus not very fast and efficient.

is_prime.sh

#!/usr/bin/env bash
#
# Author: Liblor
# Date: 16.03.2016
# License: Creative Commons Attribution License (CC BY 4.0)
#
#
# A is_prime function in bash script using trail division,
# thus not very fast and efficient.
#


function is_prime {
    local maxi=$(echo "sqrt( $1 )+1" | bc)
    local i=0;
    if [ $1 -lt 2 ]; then
        return 1
    fi
    if [ $1 -eq 2 ]; then
        return 0
    fi
    if [ $1 -eq 3 ]; then
        return 0
    fi
    if [ $(($1%2)) -eq 0 ]; then
        return 1
    fi
    for i in $(seq 3 $maxi); do
        if [ $(($1%i)) -eq 0 ]; then
            return 1
        fi
    done
    return 0
}

for i in {1..50}; do
    if is_prime $i; then
        echo "$i is a prime"
    fi
done