fileappend.js

/*
 * Simple example of using fs methods to append to a file
 */
var sys = require('sys'),
    fs = require('fs');

fs.open('my.log', 'a', undefined, function(err, fd) {
            if(err) throw err;

            fs.write(fd, 'Appending to this file\n', undefined, undefined, function(err, written) {
                         if(err) throw err;

                         sys.puts(written + ' bytes written');

                         fs.close(fd, function(err) {
                                      if(err) throw err;

                                      fs.readFile('my.log', function(err, data) {
                                                      if(err) throw err;

                                                      sys.puts(data); 
                                                  });
                                  });
                     });
        });