Node.js学习之路08——fs文件系统之stream流的基本介绍

• fs模块中集中文件读写方法的区别

• 流的概念

• Node.js中各种用于读取数据的对象

9.1 使用ReadStream对象读取文件

• fs.createReadStream(path,[options])

• options参数@H_618_135@

  • flags: 'r',//default,
  • encoding: 'utf8',//base64,ascii,null(default),
  • autoClose: true(default),//false
  • start: 使用整数值来指定文件的开始读取位置
  • end: 使用整数值来指定文件的结束读取位置

const fs = require('fs');
let filename = './one.js'
let file = fs.createReadStream(filename,{
    start: 0,end: 100,encoding: 'utf8'
});

file.on('open',(fd) => {
    console.log('open file and start read this file stream..');
});

file.pause(); // 暂停读取文件流

file.on('data',(data) => {
    console.log(`读取到文件内容,${data}`);
});

file.resume(); // 恢复读取文件流

file.on('end',() => {
    console.log('文件读取结束');
});

file.on('close',() => {
    console.log('文件关闭');
});

file.on('error',(err) => {
    console.log(`文件读取错误,${err}`);
});
/***
 * open file and start read this file stream..
 * 读取到文件内容,Hello
 * 文件读取结束
 * 文件关闭
 */

9.2 使用WriteStream对象写入文件

• fs.createWriteStream(path,[options])

const fs = require('fs');
let readFilename = './readFilename.js';
let writeFilename = './writeFilename.js';
let readFile = fs.createReadStream(readFilename,encoding: 'utf8'
});
let writeFile = fs.createWriteStream(writeFileName);
readFile.on('data',(data) => {
    writeFile.write(data,() => {
        console.log('write writeFilename.js');
        console.log(data);
    })
});

readFile.on('open',(fd) => {
    console.log(`open readFilename.js`);
});

readFile.on('end',() => {
    writeFile.end('byebye',() => {
        console.log('writeFile.js end');
        console.log(`${writeFile.bytesWritten}`)
    });
});
/***
 * open readFilename.js
 * write writeFilename.js
 * console.log('this is readFilename.js');
 * writeFile.js end
 * 45 
 */