深入nodejs中流(stream)的理解

var source = fs.readFileSync('/path/to/source', {encoding: 'utf8'});
fs.writeFileSync('/path/to/dest', source);

var fs = require('fs');
var readStream = fs.createReadStream('/path/to/source');
var writeStream = fs.createWriteStream('/path/to/dest');

readStream.on('data', function(chunk) { // 当有数据流出时，写入数据
  writeStream.write(chunk);
});

readStream.on('end', function() { // 当没有数据时，关闭数据流
  writeStream.end();
});

var fs = require('fs');
var readStream = fs.createReadStream('/path/to/source');
var writeStream = fs.createWriteStream('/path/to/dest');

readStream.on('data', function(chunk) { // 当有数据流出时，写入数据
  if (writeStream.write(chunk) === false) { // 如果没有写完，暂停读取流
    readStream.pause();
  }
});

writeStream.on('drain', function() { // 写完后，继续读取
  readStream.resume();
});

readStream.on('end', function() { // 当没有数据时，关闭数据流
  writeStream.end();
});

// pipe自动调用了data,end等事件
fs.createReadStream('/path/to/source').pipe(fs.createWriteStream('/path/to/dest'));

var fs = require('fs'),
  path = require('path'),
  out = process.stdout;

var filePath = '/Users/chen/Movies/Game.of.Thrones.S04E07.1080p.HDTV.x264-BATV.mkv';

var readStream = fs.createReadStream(filePath);
var writeStream = fs.createWriteStream('file.mkv');

var stat = fs.statSync(filePath);

var totalSize = stat.size;
var passedLength = 0;
var lastSize = 0;
var startTime = Date.now();

readStream.on('data', function(chunk) {

  passedLength += chunk.length;

  if (writeStream.write(chunk) === false) {
    readStream.pause();
  }
});

readStream.on('end', function() {
  writeStream.end();
});

writeStream.on('drain', function() {
  readStream.resume();
});

setTimeout(function show() {
  var percent = Math.ceil((passedLength / totalSize) * 100);
  var size = Math.ceil(passedLength / 1000000);
  var diff = size - lastSize;
  lastSize = size;
  out.clearLine();
  out.cursorTo(0);
  out.write('已完成' + size + 'MB, ' + percent + '%, 速度：' + diff * 2 + 'MB/s');
  if (passedLength < totalSize) {
    setTimeout(show, 500);
  } else {
    var endTime = Date.now();
    console.log();
    console.log('共用时：' + (endTime - startTime) / 1000 + '秒。');
  }
}, 500);

ln -s /path/to/copy.js /usr/local/bin/mycopy