libarphelper.sh

#!/bin/bash

function arp_mac_to_dns() {
        all_results=$(/usr/sbin/arp -a)
        declare -A mac_to_dns;
        OLDIFS=$IFS
        IFS=$'\n'
        for item in $all_results; do
                IFS=' '
                read -r dns ip at mac eth on port <<< "$item"
                if [[ "$dns" == "?" || $mac == "<incomplete>" ]]; then
                continue;
                fi
                mac_to_dns["$mac"]="$dns"
        done
        IFS=OLDIFS
        declare -p mac_to_dns
}

function arp_mac_to_ip() {
        all_results=$(/usr/sbin/arp -a)
        declare -A mac_to_ip;
        OLDIFS=$IFS
        IFS=$'\n'
        for item in $all_results; do
                IFS=' '
                read -r dns ip at mac eth on port <<< "$item"
                if [[ $mac == "<incomplete>" ]]; then
                continue;
                fi
                ip=${ip#*(}
                ip=${ip%)*}
                mac_to_ip["$mac"]="$ip"
        done
        IFS=OLDIFS
        declare -p mac_to_ip
}
function arp_ip_to_mac() {
        all_results=$(/usr/sbin/arp -a)
        declare -A ip_to_mac;
        OLDIFS=$IFS
        IFS=$'\n'
        for item in $all_results; do
                IFS=' '
                read -r dns ip at mac eth on port <<< "$item"
                if [[ $mac == "<incomplete>" ]]; then
                continue;
                fi
                ip=${ip#*(}
                ip=${ip%)*}
                ip_to_mac["$ip"]="$mac"
        done
        IFS=OLDIFS
        declare -p ip_to_mac
}