title: What the scenario call fs.close is necessary
body: <p>I can't find more about fs.close explain in nodejs API.
  I want to know what the scenario call fs.close is necessary.
  for example:</p>
  
  <pre>
  var fs =  require('fs');
  fs.writeFile("/home/a.tex","abc"); or like fs.appendFile("/home/a.tex","close")
  fs.close(); //is it necessary?
  </pre>
  
  <p>Are there any effects if i don't call fs.close?</p>
  
  <p>Any help is appreciated. </p>