Creates a multicast routing after the user inputs a valid network interface and then it lists the routing table.

mc_routing.sh

#!/bin/bash

# Creating an array containing all network interfaces which are up
net_array=()
for iface in $(ifconfig | cut -d ' ' -f1| tr ':' '\n' | awk NF)
do
        net_array+=("$iface")
done
unset "net_array[${#net_array[@]}-1]"

printf "\nPlease select the network interface you want to use:\n"
read -r net_iface

while ! [[ "${net_array[*]}" =~ (^| )"$net_iface"( |$) ]]; do # check if the user input is valid
        echo "Please enter a valid network interface:"
        read -r net_iface
done

sudo ip r a 224.0.0.0/3 dev "$net_iface"
ip r