a fast way for dns change(based on systemd) - Especially for Iranians

dns-changer.sh

#!/bin/bash

dns1=(78.157.42.100 78.157.42.101)
dns2=(178.22.122.100 185.51.200.2)
dns3=(172.29.2.100 172.29.0.100)
dns4=(185.55.226.26 185.55.225.25)

echo "0) Reset to default"
echo "1) Electro"
echo "2) Shecan"
echo "3) Hostiran"
echo "4) Begzar"
echo "5) Exit"
read -p "What is your choice? " choice

case $choice in
    0)
        resolvectl revert wlan0 # change wlan0 to your device
        resolvectl flush-caches
        echo "DNS settings reset to default."
        exit 0
        ;;
    1)
        selected_dns=("${dns1[@]}")
        ;;
    2)
        selected_dns=("${dns2[@]}")
        ;;
    3)
        selected_dns=("${dns3[@]}")
        ;;
    4)
        selected_dns=("${dns4[@]}")
        ;;
    5)
        echo "See you later :)"
        exit 0
        ;;
    *)
        echo "Not Found! :|"
        exit 1
        ;;
esac

resolvectl flush-caches
resolvectl dns wlan0 "${selected_dns[@]}" # change wlan0 to your device
resolvectl status