Sar Script by Enlik v 1.02

#!/bin/sh

# display sar network statistics in a friendly way

# by Enlik
# this script (that tries to be portable!)
# is in public domain

# put the interface name here or specify as parameter
# if you specify a parameter passed to the script, it
# will be used as interface name, overriding the variable
# below; default: eth0
interface="${1:-eth0}"

# set interval here (the first numeric argument to sar)
# defaults to 1 second
# it can be overriden with second parameter passed to
# the script
sardelay="${2:-1}"

die() {
	echo "$1" >&2
	exit 1
}

if [ ! -n "$interface" ]; then
	die "empty interface"
fi

out=$(ifconfig "$interface") || die "ifconfig error, interface = $interface"

# note: IPv4
myip=$(echo "x$out" | sed -n "s/.*inet addr:\([^ ]*\).*/\1/p")

# we need fixed field positions, which would break with time like "02:25:00 AM"
# ("sanity checks" FTW!)
export LC_TIME=C

# simple sanity checks
which sar > /dev/null 2>&1 || die "can't find sar command"
full_sar=$(sar -n DEV 1 1) || die "sanity check (1) failed: can't run sar; interface = $interface"
echo "$full_sar" | grep -F -q "$interface" || die "sanity check (2) failed: no output for interface $interface"
echo "$full_sar" | awk '{
		iface=0;
		if (/IFACE/) {
			iface=1;
			if ($5 == "rxkB/s" && $6 == "txkB/s") {
				exit 0
			} else {
				exit 1
			}
		}
	}
	END {
		if (iface != 1)
			exit 2
	}
' || die "santity check (3) failed - maybe you have different or broken sar? exit status: $?; output: $full_sar"

# Interface: wlan0 IP: xxx.xxx.xxx.xxx UL: 10 KB/s DL: 12 KB/s
sar -n DEV "$sardelay" | awk -v ip="$myip" -v iface="$interface" '{ if (index($0,iface)) { print "Interface:", iface, "IP:", ip, "UL:", $6, "kB/s DL:", $5, "kB/s" } }'