NIC stats from /sys/class/net/

nic-stats.sh

#!/usr/bin/env bash

width=10
declare -a stats=(rx_bytes tx_bytes rx_packets tx_packets)
declare -a names=('RX Bps ' 'TX Bps' 'RX pps' 'TX pps')
declare -a fmt=('--to iec --suffix B' '--to iec --suffix B' '--to si' '--to si')

function get_stat() {
    local iface="$1"
    local stat="$2"
    echo -n "$(< /sys/class/net/$iface/statistics/$stat)"
}

function get_all_stats() {
    local iface="$1"
    local values=()
    shift
    for stat; do
        values+=("$(get_stat "$iface" "$stat")")
    done
    echo "${values[@]}"
}

function print_header() {
    echo
    for name; do
        printf "%${width}s" "$name"
    done
    echo
    echo
}

iface="${1:-lo}"
echo "# iface '$iface'" >&2

declare -a prev curr

n=0
prev=($(get_all_stats "$iface" "${stats[@]}"))
while sleep 1; do
    if [ $((n % 10)) = 0 ]; then
        print_header "${names[@]}" >&2
    fi

    curr=($(get_all_stats "$iface" "${stats[@]}"))

    for (( i = 0 ; i < "${#stats[@]}" ; i++ )) ; do
        metric=$((${curr[$i]} - ${prev[$i]}))
        printf "%${width}s" "$(numfmt "$metric" ${fmt[$i]})"
    done
    echo

    prev=("${curr[@]}")
    n=$((n + 1))
done