Show network activity

net_activity.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"strconv"
	"strings"
	"time"
)

const (
	rx_bytes = "/statistics/rx_bytes"
	tx_bytes = "/statistics/tx_bytes"
	interval = 2 * time.Second
)

func main() {
	log.SetFlags(log.Ltime | log.Lshortfile)
	if len(os.Args) < 2 {
		fmt.Fprintf(os.Stderr, "Usage: %s eth0\n", os.Args[0])
		os.Exit(1)
	}
	ifname := os.Args[1]
	base := "/sys/class/net/" + ifname

	read := func(f string) uint64 {
		cnt, err := readCount(f)
		if err != nil {
			os.Exit(2)
		}
		return cnt
	}
	tx0 := read(base + tx_bytes)
	rx0 := read(base + rx_bytes)

	ticker := time.NewTicker(interval)
	defer ticker.Stop()
loop:
	for {
		select {
		case t, ok := <-ticker.C:
			if !ok {
				break loop
			}
			tx := read(base + tx_bytes)
			rx := read(base + rx_bytes)
			output(t, tx, rx, tx0, rx0, interval)
			tx0 = tx
			rx0 = rx
		}
	}
}

func output(t time.Time, tx, rx, tx0, rx0 uint64, interval time.Duration) {
	nsec := float64(interval / time.Second)
	txs := float64(tx-tx0) / nsec / 1024
	rxs := float64(rx-rx0) / nsec / 1024
	fmt.Printf("t=%d, tx=%d, rx=%d, tx/s=%.1f KB/s, rx/s=%.1f KB/s\n", t.Unix(), tx, rx, txs, rxs)
}

func readCount(f string) (uint64, error) {
	b, err := ioutil.ReadFile(f)
	if err != nil {
		log.Print(err)
		return 0, err
	}
	cnt, err := strconv.ParseUint(strings.TrimSpace(string(b)), 10, 64)
	if err != nil {
		log.Print(err)
		return 0, err
	}
	return cnt, nil
}