#!/bin/sh
##
## SCRIPT NAME: get_net_stats.sh
##
## PURPOSE:
##    Gets 'RX' (received) and 'TX' (transmitted) data from output of
##    the 'netstat' command (or some other command supplying the same data).
##
##+############################################
## Example output from the 'netstat -i' command:
##
## Kernel Interface table
## Iface   MTU Met   RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
## eth0       1500 0     23449      0      0 0         19670      0      0      0 BMRU
## lo        16436 0         4      0      0 0             4      0      0      0 LRU
## wlan0      1500 0         0      0      0 0             0      0      0      0 BMU
## wmaster0      0 0         0      0      0 0             0      0      0      0 RU
##
##+#########################################################
## ALTERNATIVELY, we could use 'ifconfig -a -s', which gives:
## 
## Iface   MTU Met   RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
## eth0       1500 0     23449      0      0 0         19670      0      0      0 BMRU
## lo        16436 0         4      0      0 0             4      0      0      0 LRU
## wlan0      1500 0         0      0      0 0             0      0      0      0 BMU
## wmaster0      0 0         0      0      0 0             0      0      0      0 RU
##
## where '-a' stands for 'all' --- and '-s' stand for 'summary'.
##+########################################################################
##
## This script gets the data from the 'RX-OK' and 'TX-OK' columns.
##
## INPUT: a single argument supplies an interface ID, such as
##                                      'eth0' or 'eth1' or 'wlan0'.
##
## CALLED BY: a Tk GUI script that shows 'RX' and 'TX' DIFFERENCE data
##            --- i.e. RATE data ---
##            as needle readings on a couple of meters (dials) drawn
##            on a Tk canvas --- Tk script name:
##                    meters_net_stats.tk
##
## MAINTENANCE HISTORY:
## Updated by: Blaise Montandon 2013sep05 Started this script on Linux,
##                                        using Ubuntu 9.10 (2009 October,
##                                        'Karmic Koala').
## Updated by: Blaise Montandon 20.......
##+########################################################################

## FOR TESTING:
# set -x

if test "$1" = ""
then
   echo "ERROR: Missing argument. Need a network interface ID."
   exit
fi

## ALTERNATIVE:
# ifconfig -a -s | grep "^$1" | awk '{print $4 " " $8}'

netstat -i | grep "^$1" | awk '{print $4 " " $8}'