text: var util = require('util');
  
  var stdio = module.exports = {};
  
  // constant
  stdio.DEBUG = 0;
  stdio.INFO = 1;
  stdio.WARN = 2;
  stdio.ERROR = 3;
  
  // current level
  stdio.level = stdio.INFO;
  
  stdio.write = function() {
      if (stdio.level <= stdio.INFO) {
          process.stdout.write(util.format.apply(util, arguments));
      }
  };
  
  stdio.debug = function() {
      if (stdio.level <= stdio.DEBUG) {
          process.stderr.write(util.format.apply(util, arguments) + '\n');
      }
  };
  
  stdio.info = function() {
      if (stdio.level <= stdio.INFO) {
          process.stderr.write(util.format.apply(util, arguments) + '\n');
      }
  };
  
  stdio.warn = function() {
      if (stdio.level <= stdio.WARN) {
          process.stderr.write(util.format.apply(util, arguments) + '\n');
      }
  };
  
  stdio.error = function() {
      if (stdio.level <= stdio.ERROR) {
          process.stderr.write(util.format.apply(util, arguments) + '\n');
      }
  };
  
  stdio.readline = function(callback, thisArg) {
      process.stdin.setEncoding('utf8');
      process.stdin.once('data', function(data) {
          callback.call(thisArg, data.toString().trim());
      }).resume();
  };
  