How to read a file in blocks with node?

Question

I need to read a file in node but, for example, if the size of the file is 4KB I need to read the first 1K and print it on the console, then, the second Kb of the file... and continue to the end. The problems is that I don't know how to "stop" reading after the first Kb and continue afterwards by there.

Any help?

Thanks¡¡

Answer 1

You can use fs.read to read a fixed number of bytes and async to loop.

untested code:

var buf = new Buffer();
var length=4096; // you can get this with fs.stat
var position=0;
fs.open('/tmp/file', 'r', function(err, fd) {
  if(err) throw err;

  async.whilst(
    function() { position < length; },
    function(callback) {
      fs.read(fd, buf, null, 1024, position, function(err, bytesRead, buf) {
        if(err) callback(err);
        if(bytesRead!=1024) throw new Error('bytes read not 1024');
        console.log(buf.toString());
        position+=bytesRead;
        callback(); 
      });
    },
    function(err) {
      if(err) throw err;
    }
  );
});