If output of bash command is empty, do something

Hi I am new to bash so please excuse me if I have a really silly/easy question. I am writing a script which allows the user to change their region (for wireless). What I am wanting to do is put a check in place, so if they type in an incorrect value, it brings up the prompt again to input the region. I want to do this by checking if the output of the command sudo iw reg set $reg, if it is a correct input, there is no output. But if it is a wrong input, it gives an error message. I tried to do this but im getting an error:

#!/bin/bash
echo "Please set a region: " 
read reg

if [(sudo iw reg set $reg) -ne 0]; then
    echo "Please set a valid region: "  
    read reg

else    
    echo "Setting reg as $reg"
    sudo iw reg set $reg 
fi

Thanks in advance