#!/bin/sh

# Ce script donne la volumétrie d'une interface réseau à intervalle régulier
# (se base sur /proc/net/dev)

FICHIER_PROC=/proc/net/dev
DELAI="1"

# Try to get a pretty formatter
FORMATTER="cat -"
if which numfmt >/dev/null 2>&1; then
	FORMATTER="numfmt --field 2-3 --to si --padding 7"
fi

# Factorize the parsing
getdata() {
	cat "$1" | sed -e '1d;2d' -e 's/^[[:space:]]*//' -e 's/[[:space:]]\+/ /g' | cut -f 1,2,10 -d " "
}

# First grab
OLDDATA="$( getdata "$FICHIER_PROC" )"

while sleep "$DELAI" ; do
	NEWDATA="$( getdata "$FICHIER_PROC" )"

	# header
	printf "\n% 15s\t% 6s\t% 6s\n" " " "IN" "OUT"

	echo "$NEWDATA" | while read INTERFACE VOLUME_IN VOLUME_OUT; do
		# Again, scope issues with read and pipes so we make a one-time loop :)
		echo "$OLDDATA" | grep "$INTERFACE" | while read DUMP OLD_VOLUME_IN OLD_VOLUME_OUT; do
			VOLUME_IN="$(( $VOLUME_IN - $OLD_VOLUME_IN ))"
			VOLUME_OUT="$(( $VOLUME_OUT - $OLD_VOLUME_OUT ))"
			printf "% 15s\t%d\t%d\n" "$INTERFACE" "$VOLUME_IN" "$VOLUME_OUT" | $FORMATTER
		done
	done

	OLDDATA="$NEWDATA"
done