Tiny Networkinterface Monitor (TNM) was written to practice bash scripting. It's analyzing any interface usage (I used it for my DSL connection) . I generates a pseudo graphical representation of the receive and send usage in % of the interface bandwidth an usage in KBs .
Download the script from here in a local directory and customize it to the local environment. The parameters to customized are marked in the script.
Adapt the following parameters:
1) max transmission speed in KB/s 2) max receiving speed in KB/s 3) Measurement interval in seconds 4) Scrren width in number of chars
Invocation without a parameter or any parameter. If a parameter was passed th max xmit and rcv speed is not used to calculate the bandwidth.