fs.fsyncSync(fd)

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

fs.fsyncSync = function(fd) {
  return binding.fsync(fd);
};