kill process ubuntu

C++
pidof slack 
9734 9718 9716 9708 9622 9619
sudo kill -9 process_id

pidof apt 
9734 9718 9716 9708 9622 9619
sudo kill -9 9734 9718 9716 9708 9622 9619 
sudo kill -9 process_idps -ax | grep application name
Source

Also in C++: