ifmeter_node.js

var fs = require('fs');

function readLines(input, func) {
  var remaining = '';
  var lines = [];

  input.on('data', function(data) {
    remaining += data;
    var index = remaining.indexOf('\n');
    while (index > -1) {
      var line = remaining.substring(0, index);
      remaining = remaining.substring(index + 1);
      //func(line);
      lines.push(line);
      index = remaining.indexOf('\n');
    }
  });

  input.on('end', function() 
  {
    if (remaining.length > 0) 
    {
      lines.push(remaining);
      return func(lines);
    }
    func(lines);
  });
}


var data = [];

setInterval(function()
{
 var input = fs.createReadStream('/proc/net/dev'),
	linesInterfaces = [],
	interfaces = {};

  readLines(input, function(lines)
  {
	linesInterfaces = lines.splice(2);

	linesInterfaces.forEach(function(ifLine)
	{
	    var ifData = ifLine.split(':'),
		ifName = ifData[0].trim(),
    		ifValues = ifData[1].split(' ').filter(function(v){  
		    var intV = parseInt(v);
		    return !isNaN(intV);
		}).map(function(v)
		{
		    return parseInt(v)
		});

	    interfaces[ifName] = ifValues;
	});

	data.push(interfaces);

	if( data.length > 1 )
	{
	    var l_data = data[data.length - 1],
		r_data = data[data.length - 2],
		l_size = l_data.length,
		r_size = r_data.length,
		if_data = l_size > r_size ? l_data : r_data;

		Object.keys(if_data).forEach(function(if_name)
		{
		    if( l_data[if_name] == 'undefined' || r_data[if_name] == 'undefined' )
		    {
			console.log( 'if: ' + if_name + ' is down' );
		    }
		    else 
		    {
			var l_v = l_data[if_name][0];
			var r_v = r_data[if_name][0];
			
			console.log( 'if: ' + if_name + ' : ' + (l_v - r_v) );
		    }

		});
	}

    });
}, 1000);

// bytes packets errs drop fifo frame compressed multicast
// bytes packets errs drop fifo colls carrier compressed