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作者: 黄杰；
标签: fs模块

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文件系统（File System）

基本概念

• 服务器的本质就是将本地的文件发送给远程客户端
• 学习fs模块的API
• 使用fs模块前，需要引入 cost fs = require('fs');

特点

• 提供同步异步两种选择
• 同步导致阻塞
• 异步操作完成通过回调返回结果

使用

同步写入操作

let fs = require("fs");

//同步打开文件
let fd = fs.openSync('text_1', 'w');
console.log(fd)

//写入内容
fs.writeFileSync(fd, 'hello ink!');

//退出
fs.closeSync(fd);

异步写入操作

let fs = require("fs");

fs.open("text_2.txt", "w", (err, fd) => {
    if( !err ) {
        fs.writeFile(fd, 'ink nice to meet u!!', (err) => {
            if( !err ) {
                console.log('success');
                fs.close(fd, (err) => {
                    if ( !err ) {
                        console.log('file closed');
                    } else {
                        throw err;
                    }
                })
            } else {
                throw err;
            }
        });
    } else {
        throw err;
    }
})

文件流写入操作

let fs = require("fs");

let ws = fs.createWriteStream('text_3.txt');

//打开通道
ws.once('open', () => {
    console.log('通道已打开！')
})

ws.write("what's your name?\n");
ws.write("what's your name?\n");
ws.write("what's your name?\n");
ws.write("what's your name?\n");

ws.end();

//监听通道关闭
ws.once('close', () => {
    console.log('通道已关闭！')
})

文件读取操作

读取图片并写入到另一个文件中(单个文件操作)

let fs = require("fs");

fs.readFile("../images/deskPic1.jpg", (err, data) => {
    if ( !err ) {
        console.log(data);
        //写入图片文件
        fs.writeFile('receiveimage_1.jpg', data, (err, data) => {
            if ( !err ) {
                console.log('transfer success!');
            } else {
                throw err;
            }
        })
    } else {
        throw err;
    }
})

使用文件读入流处理

let fs = require("fs");

let readStream = fs.createReadStream("../images/deskPic2.jpg"); 

let writeStream = fs.createWriteStream("receiveimage_2.jpg");

//监听文件流打开关闭
readStream.once('open', () => {
    console.log('readstream opened');
})

readStream.once('clos', () => {
    console.log('readstream closed');
})

writeStream.once('open', () => {
    console.log('writeStream opened');
})

writeStream.once('clos', () => {
    console.log('writeStream closed');
})

//读入流操作
readStream.on('data', (data) => {
    console.log(data);
    //文件过大时分段读取
    //写入
    writeStream.write(data);
})

简便方法

let fs = require("fs");

let readStream = fs.createReadStream("../images/deskPic2.jpg"); 

let writeStream = fs.createWriteStream("receiveimage_2.jpg");

//创建管道

readStream.pipe(writeStream);