title: callback in fs.write is not working as document
body: <p>as node.js document</p>
  
  <blockquote>
    <p>fs.write(fd, buffer, offset, length, position, [callback])</p>
  </blockquote>
  
  <p>So I wrote like:</p>
  
  <pre><code>var fs = require('fs');
  
  fs.open('./example.txt', 'a', 0666, function(err, fd) {
    if (err) { throw err; }
    console.log('file opened');
    fs.write(fd, 'test', null, null, null, function(err) {
      if (err) { throw err; }
      console.log('file written');
      fs.close(fd, function() {
        console.log('file closed');
      });
    });
  });
  </code></pre>
  
  <p>but callback of fs.write is not fired. output is just 'file opended'.</p>
  
  <pre><code>fs.write(fd, 'test', null, null, function(err) {
  </code></pre>
  
  <p>but I assign callback for 5th parameter not 6th. this is works.
  Why defferent with document.</p>
  
  <p>and in node source( node_file.cc ) callback is 6th parameter.</p>
  
  <pre><code> Local&lt;Value&gt; cb = args[5];
  </code></pre>
  
  <p>I don't understand. </p>