How can I get the current network interface throug

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Tools such as MRTG provide network throughput / bandwidth graphs for the current network utilisation on specific interfaces, such as eth0. How can I return that information at the command line on Linux/UNIX?

Preferably this would be without installing anything other than what is available on the system as standard.

Answer 1

You can parse the output of ifconfig

Answer 2

I couldn't get the parse ifconfig script to work for me on an AMI so got this to work measuring received traffic averaged over 10 seconds

date && rxstart=`ifconfig eth0 | grep bytes | awk '{print $2}' | cut -d : -f 2` && sleep 10 && rxend=`ifconfig eth0 | grep bytes | awk '{print $2}' | cut -d : -f 2` && difference=`expr $rxend - $rxstart` && echo "Received `expr $difference / 10` bytes per sec"

Sorry, it's ever so cheap and nasty but it worked!

Answer 3

I wrote this dumb script a long time ago, it depends on nothing but Perl and Linux≥2.6:

#!/usr/bin/perl

use strict;
use warnings;

use POSIX qw(strftime);
use Time::HiRes qw(gettimeofday usleep);

my $dev = @ARGV ? shift : 'eth0';
my $dir = "/sys/class/net/$dev/statistics";
my %stats = do {
    opendir +(my $dh), $dir;
    local @_ = readdir $dh;
    closedir $dh;
    map +($_, []), grep !/^\.\.?$/, @_;
};

if (-t STDOUT) {
    while (1) {
        print "\033[H\033[J", run();
        my ($time, $us) = gettimeofday();
        my ($sec, $min, $hour) = localtime $time;
        {
            local $| = 1;
            printf '%-31.31s: %02d:%02d:%02d.%06d%8s%8s%8s%8s',
            $dev, $hour, $min, $sec, $us, qw(1s 5s 15s 60s)
        }
        usleep($us ? 1000000 - $us : 1000000);
    }
}
else {print run()}

sub run {
    map {
        chomp (my ($stat) = slurp("$dir/$_"));
        my $line = sprintf '%-31.31s:%16.16s', $_, $stat;
        $line .= sprintf '%8.8s', int (($stat - $stats{$_}->[0]) / 1)
            if @{$stats{$_}} > 0;
        $line .= sprintf '%8.8s', int (($stat - $stats{$_}->[4]) / 5)
            if @{$stats{$_}} > 4;
        $line .= sprintf '%8.8s', int (($stat - $stats{$_}->[14]) / 15)
            if @{$stats{$_}} > 14;
        $line .= sprintf '%8.8s', int (($stat - $stats{$_}->[59]) / 60)
            if @{$stats{$_}} > 59;
        unshift @{$stats{$_}}, $stat;
        pop @{$stats{$_}} if @{$stats{$_}} > 60;
        "$line\n";
    } sort keys %stats;
}

sub slurp {
    local @ARGV = @_;
    local @_ = <>;
    @_;
}

It just reads from /sys/class/net/$dev/statistics every second, and prints out the current numbers and the average rate of change:

$ ./net_stats.pl eth0
rx_bytes                       :  74457040115259 4369093 4797875 4206554 364088
rx_packets                     :     91215713193   23120   23502   23234  17616
...
tx_bytes                       :  90798990376725 8117924 7047762 7472650 319330
tx_packets                     :     93139479736   23401   22953   23216  23171
...
eth0                           : 15:22:09.002216      1s      5s     15s     60s

                                ^ current reading  ^-------- averages ---------^

Answer 4

You could parse /proc/net/dev.

Answer 5

I got another quick'n'dirty bash script for that:

#!/bin/bash
IF=$1
if [ -z "$IF" ]; then
        IF=`ls -1 /sys/class/net/ | head -1`
fi
RXPREV=-1
TXPREV=-1
echo "Listening $IF..."
while [ 1 == 1 ] ; do
        RX=`cat /sys/class/net/${IF}/statistics/rx_bytes`
        TX=`cat /sys/class/net/${IF}/statistics/tx_bytes`
        if [ $RXPREV -ne -1 ] ; then
                let BWRX=$RX-$RXPREV
                let BWTX=$TX-$TXPREV
                echo "Received: $BWRX B/s    Sent: $BWTX B/s"
        fi
        RXPREV=$RX
        TXPREV=$TX
        sleep 1
done

It's considering that sleep 1 will actually last exactly one second, which is not true, but good enough for a rough bandwidth assessment.

Thanks to @ephemient for the /sys/class/net/<interface>! :)

Answer 6

I like iptraf but you probably have to install it and it seems to not being maintained actively anymore.