There are many ways how to get the current bandwidth usage on Linux. This is a very simple shell script that lists the network statistic every second: #!/bin/bash
if [ -z "$1" ]; then
       [ ... ]

"lsof" is a command which lists all open open files on a system. And because everything is a file in Unix (this includes pipes, network sockets, disk files and all other devices) it is a bit like a sw [ ... ]