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Realtime bandwidth terminal graph visualization

Written by Solène, on 19 July 2019.
Tags: #openbsd65

If for some reasons you want to visualize your bandwidth traffic on an interface (in or out) in a terminal with a nice graph, here is a small script to do so, involving ttyplot, a nice software making graphics in a terminal.

The following will works on OpenBSD. You can install ttyplot by pkg_add ttyplot as root, ttyplot package appeared since OpenBSD 6.5.

For Linux, the ttyplot official website contains tons of examples.

Example

Output example while updating my packages:

                                          IN Bandwidth in KB/s
  ↑ 1499.2 KB/s#
  │            #
  │            #
  │            #
  │            ##
  │            ##
  │ 1124.4 KB/s##
  │            ##
  │            ##
  │            ##
  │            ##
  │            ##
  │ 749.6 KB/s ##
  │            ##
  │            ##
  │            ##                                                    #
  │            ##      # #       #                     #             ##
  │            ##  #   ###    # ##      #  #  #        ##            ##         #         # ##
  │ 374.8 KB/s ## ##  ####  # # ## # # ### ## ##      ###  #      ## ###    #   #     #   # ##   #    ##
  │            ## ### ##### ########## #############  ###  # ##  ### ##### #### ##    ## ###### ##    ##
  │            ## ### ##### ########## #############  ###  ####  ### ##### #### ## ## ## ###### ##   ###
  │            ## ### ##### ########## ############## ###  ####  ### ##### #### ## ## ######### ##  ####
  │            ## ### ##### ############################## ######### ##### #### ## ## ############  ####
  │            ## ### #################################################### #### ## #####################
  │            ## ### #################################################### #############################
  └────────────────────────────────────────────────────────────────────────────────────────────────────→
     # last=422.0 min=1.3 max=1499.2 avg=352.8 KB/s                             Fri Jul 19 08:30:25 2019
                                                                           github.com/tenox7/ttyplot 1.4

In the following command, we will use trunk0 with INBOUND traffic as the interface to monitor.

At the end of the article, there is a command for displaying both in and out at the same time, and also instructions for customizing to your need.

Article update: the following command is extremely long and complicated, at the end of the article you can find a shorter and more efficient version, removing most of the awk code.

You can copy/paste this command in your OpenBSD system shell, this will produce a graph of trunk0 inbound traffic.

{ while :; do netstat -i -b -n ; sleep 1 ; done } | awk 'BEGIN{old=-1} /^trunk0/ { if(!index($4,":") && old>=0)  { print ($5-old)/1024 ; fflush  ; old = $5 } if(old==-1) { old=$5 } }'  | ttyplot -t "IN Bandwidth in KB/s" -u "KB/s" -c "#"

The script will do an infinite loop doing netstat -ibn every second and sending that output to awk. You can quit it with Ctrl+C.

Explanations

Netstat output contains total bytes (in or out) since system has started so awk needs to remember last value and will display the difference between two output, avoiding first value because it would make a huge spike (aka the total network transfered since boot time).

If I decompose the awk script, this is a lot more readable. Awk is very readable if you take care to format it properly as any source code!

#!/bin/sh
{ while :;
  do
      netstat -i -b -n
      sleep 1
  done
} | awk '
    BEGIN {
        old=-1
    }
    /^trunk0/ { 
        if(!index($4,":") && old>=0) {
            print ($5-old)/1024
            fflush
            old = $5
        }
        if(old==-1) {
            old = $5
        }
    }' | ttyplot -t "IN Bandwidth in KB/s" -u "KB/s" -c "#"

Customization

  • replace trunk0 by your interface name
  • replace both instances of $5 by $6 for OUT traffic
  • replace /1024 by /1048576 for MB/s values
  • remove /1024 for B/s values
  • replace 1 in sleep 1 by another value if you want to have the value every n seconds

IN/OUT version for both data on the same graph + simpler

Thanks to leot on IRC, netstat can be used in a lot more efficient way and remove all the awk parsing! ttyplot supports having two graphs at the same time, one being in opposite color.

netstat -b -w 1 -I trunk0 | awk 'NR>3 { print $1/1024; print $2/1024; fflush }' | ttyplot -2 -t "IN/OUT Bandwidth in KB/s" -u "KB/s" -c "#"