fs.fsync(fd, [callback(err)])

var fs = require('fs');
fs.open('content.txt', 'a', function(err,fd){
 if(err){
  throw err;
 }
 console.log('file open');
 fs.fsync(fd, function(err){
  if(err){
   throw err;
  }
  console.log('done');
  fs.close(fd,function(err){
   if(err){
    throw err;
   }
   console.log('file closed');
  })
 })
})

fs.fsync(fd, callback)fs.fsync = function(fd, callback) {
  binding.fsync(fd, makeCallback(callback));
};