based on ip tool it checks RX and TX value of specified interface within some interval and provide speed in KB
Usage: ./check_net.sh -i dev -t int>0 -w int>0 -c int>0 Options: -h show this page; -t time interval between checks, in sec (default = 1sec); -i name of network interface; -w warning level (in KB) integer more then zero; -c critical level (in KB) integer more then zero;