Lookup CPU usage in details

cpu-watch.js

/*
  USAGE: node cpu-watch.js <pid> <how-many-minutes>
*/

var fs = require('fs');
var format = require('util').format;

var PID = process.env.PID || process.argv[2];
if(!PID) throw new Error('No PIC Provided!');
var ENDIN_MINUTES = process.env.ENDIN_MINUTES || process.argv[3];

var INTERVAL_MILLIES = 2000;

var startedAt = Date.now();
var startedTimes;
var previous = {};

processTimes();
var processTimesInterval = setInterval(processTimes, INTERVAL_MILLIES);
process.on('SIGINT', atTheEnd);
if(ENDIN_MINUTES) {
  setTimeout(atTheEnd, ENDIN_MINUTES * 1000 * 60);
}

function processTimes(processTimes) {
  var times = getTimes();
  if(!startedTimes) startedTimes = times;

  if(previous.times) {
    var sectionTimes = getSectionTimes(times, previous.times, INTERVAL_MILLIES);
    console.log('%s + %s = %s (%s%)', 
      sectionTimes.stime, sectionTimes.utime, sectionTimes.total, sectionTimes.ptotal);
    previous.sectionTimes = sectionTimes;
  }

  previous.times = times;
}

function getSectionTimes(currTimes, previousTimes, elaspedMillis) {
  var sectionTimes = {};
  sectionTimes.utime = currTimes.utime - previousTimes.utime;
  sectionTimes.stime = currTimes.stime - previousTimes.stime;
  sectionTimes.total = sectionTimes.utime + sectionTimes.stime;
  sectionTimes.ptotal = ((sectionTimes.total * 1000/100) / elaspedMillis) * 100;
  sectionTimes.ptotal = sectionTimes.ptotal.toFixed(2);

  return sectionTimes;
}

function atTheEnd() {
  var times = getTimes();
  var elaspedMillis = Date.now() - startedAt;
  var elaspedSecs = (elaspedMillis/1000).toFixed(2);
  var sectionTimes = getSectionTimes(times, startedTimes, elaspedMillis);
    console.log('\nAVG(%ssec) => %s + %s = %s (%s%)', elaspedSecs,
      sectionTimes.stime, sectionTimes.utime, sectionTimes.total, sectionTimes.ptotal);
  process.exit(0);
}

function getTimes() {
  var content = fs.readFileSync(format('/proc/%s/stat', PID), 'utf8');
  content = content.substr(content.lastIndexOf(')') + 2);
  var parts = content.split(' ');

  return {
    stime: parts[12],
    utime: parts[11]
  };
}