title: grunt.js console.log in callback doesn't output anything
body: <p>What is wrong with my codes, the console.logs that is inside a call back of file related API's doesn't show anything in CLI.</p>
  
  <pre><code>module.exports = function (grunt) {
  
      var path = require("path"),
          fs = require("fs"),
          gm = require("gm");
      grunt.registerMultiTask("imagesizeslist", "Generate image sizes list", function () {
          var files = grunt.file.expandFiles(this.file.src);
          grunt.helper('imagesizeslist', files);
      });
  
      //  grunt.log.write(contents);
  
  
      grunt.registerHelper('imagesizeslist', function (files) {
          files.forEach(function (file) {
              basename = path.resolve(file);
              var exec = require('child_process').exec,
              child;
              //using sips
              console.log('sips "'+basename+'" -g pixelHeight');
              child = exec('sips "'+basename+'" -g pixelHeight',
                function (error, stdout, stderr) {
                    console.log(error);
                  console.log('stdout: ' + stdout);
              });
              // using gm
              gm(basename).size(function (err, size) {
                  if (!err)
                      console.log(size.width &gt; size.height ? 'wider' : 'taller than you');
                  else
                      console.log("test");
                  console.log(size);
              });
          });
      });
  };
  </code></pre>