Tip of the Trade: Bandwidth Monitor NG

Bandwidth Monitor New Generation (bwm-ng) is a neat little console-based live bandwidth monitor for Linux, BSD, Solaris, Mac OS X, and any other Unix-type operating system. It watches any number of interfaces, and displays both individual and total statistics. bwm-ng is easy to use yet very useful. Output can be directed to ncurses, a plain console, a comma-delimited text file, or HTML, which is handy for remote monitoring.
Bandwidth Monitor NG is a simple bandwidth monitoring tool for Unix.

This example is from a Linux router with two Ethernet interfaces:

$ bwm-ng
  bwm-ng v0.6-pre1 (probing every 0.500s), press 'h' for help
  input: /proc/net/dev type: rate
  |       iface                  Rx                   Tx                Total
  ===========================================================================
            lo:           0.00 KB/s            0.00 KB/s            0.00 KB/s
           lan:           2.13 KB/s           88.12 KB/s           90.26 KB/s
           wan:          88.12 KB/s            2.13 KB/s           90.26 KB/s
  ---------------------------------------------------------------------------
         total:          90.26 KB/s           90.26 KB/s          180.52 KB/s

That’s pretty straightforward. This shows the incoming WAN link is nearly saturated. (By a Kubuntu dist-upgrade, in case you were wondering.) When you’re wondering why a particular Web site is slow, bmw-ng might tell the tale — are fat pages that take forever to download the culprit? Or is the server slow? If your bandwidth is maxed out, it’s not a server issue.

By default, bwm-ng updates itself every half-second. To change this interval, hit the + or – keys to increase or decrease the polling interval in 100ms intervals. Hit the letter “h” to see a help menu.

bwm-ng takes a long string of options to run in HTML mode. Give the output file, designated by the -F flag, any name you want. Then, point your browser to this file, which updates every second:

$ bwm-ng -o html -R 1 -H 1 -t 1 -D 1 -F bwm.html

Bwm-ng will run from a configuration file, so you don’t have to tire your fingers with all that typing. See Gropp.org for more information.