index.js

var Readable = require('stream').Readable,
    exec = require('child_process').exec;

var clc = require('cli-color'),
    csv2 = require('csv2'),
    through2 = require('through2');

function getVolume(){
  var rs = new Readable;
  var cmd = 'osascript -e "get volume settings"';
  rs._read = function(){
    exec(cmd,function(err,stdout,stderr){
      if(err) return rs.emit('error',err);
      if(stderr) return rs.emit('error',stderr);
      rs.push(stdout);
    });
  };
  return rs 
};

function valueParser(){
  function _split(str){
    return parseInt(str.split(/:/)[1]);
  };
  return through2({objectMode: true}, function(chunk,enc,next){
    this.push({
      output: _split(chunk[0])
    });
    next();
  });
};

function show(data){
  var c = (function(n){
    var ret = [];
    for(var i=0; i<n; i++){ ret.push("\uD83C\uDE50"); }
    return ret.join('')
  })(Math.round(data.output*0.1));
  var out = [
    clc.reset,
    "\uD83C\uDFA7 ",
    c
  ].join('');
  console.log(out);
};

var volvis = getVolume().pipe(csv2()).pipe(valueParser());
volvis.on('data',show);
process.once('SIGINT',function(sig){
  volvis.push(null);
  process.exit(0);
});