Node.js基礎(chǔ) 78：創(chuàng)建和刪除目錄、流和管道

MrZONT 發(fā)布于2019-08-23 15:43 / 990人閱讀

創(chuàng)建和刪除目錄

異步創(chuàng)建刪除目錄

var fs = require("fs");

fs.mkdir("stuff", function() {
    fs.readFile("readMe.txt", "utf8", function(err, data) {
        fs.writeFile("./stuff/writeMe.txt", data, function() {
            console.log("copy successfully");
        })
    })
});
// fs.unlink("writeMe.txt", function() {
//     console.log("delete writeMe.txt file");
// })刪除文件

遞歸刪除非空文件夾

function delDir(path){
    let files = [];
    if(fs.existsSync(path)){
        files = fs.readdirSync(path);
        files.forEach((file, index) => {
            let curPath = path + "/" + file;
            if(fs.statSync(curPath).isDirectory()){
                delDir(curPath); //遞歸刪除文件夾
            } else {
                fs.unlinkSync(curPath); //刪除文件
            }
        });
        fs.rmdirSync(path);
    }
}
module.exports = delDir;

流和管道

舉例:在命令行中

ls命令:查看當(dāng)前目錄下的文件和目錄
grep:篩選,例如是否包含"app"這個(gè)關(guān)鍵字
ls輸出一個(gè)流(輸出一個(gè)信息),這個(gè)流作為了grep命令的輸入

文檔:http://nodejs.cn/api/stream.h...
例如:HTTP請(qǐng)求是輸入流,響應(yīng)是輸出流.
流的應(yīng)用:

處理數(shù)據(jù),最典型的就是http服務(wù)的時(shí)候.請(qǐng)求和響應(yīng)就是流的一種體現(xiàn),再比如對(duì)數(shù)據(jù)進(jìn)行的處理,例如webpack,gulp也大量運(yùn)用了流這個(gè)技術(shù),或者對(duì)文件進(jìn)行打包壓縮

提高讀寫(xiě)性能,與文件系統(tǒng)的讀寫(xiě)命令有所區(qū)別,文件系統(tǒng)的讀寫(xiě)文件命令是一次性把文件里的內(nèi)容放到內(nèi)存當(dāng)中,如果文件很大,用這種命令就不太合適,要用流來(lái)處理,流會(huì)把內(nèi)容放到buffer(緩存)中,一邊放一邊處理,這樣的話性能就會(huì)很高

//把讀取的文件放入一個(gè)流中
var fs = require("fs")
var myReadStream = fs.createReadStream(__dirname + "/readMe.txt")
//流是一個(gè)事件的實(shí)例,所以可以放置監(jiān)聽(tīng)事件(流可以是可讀的、可寫(xiě)的、或者可讀可寫(xiě)的。 所有的流都是 EventEmitter 的實(shí)例。)
myReadStream.on("data",function(chunk) {//chunk是塊的意思
    console.log("new chunk received")
    console.log(chunk)
})

readMe.txt文件有5000行的字符,把文件分成一個(gè)個(gè)buffer,分段處理

在參數(shù)里加utf-8,會(huì)發(fā)現(xiàn),把那段字符打印出來(lái).

on是在接收數(shù)據(jù)的時(shí)候的監(jiān)聽(tīng)函數(shù),end代表在接受數(shù)據(jù)完成之后的數(shù)據(jù)

var fs = require("fs")
var myReadStream = fs.createReadStream(__dirname + "/readMe.txt")
myReadStream.setEncoding("utf8")//編碼也可以這樣寫(xiě)
var data = ""
myReadStream.on("data",function(chunk) {
    data+=chunk
})
myReadStream.on("end",function () {
    console.log(data)
})

以上就是把一個(gè)readMe.txt當(dāng)做一個(gè)流來(lái)處理.

如何寫(xiě)一個(gè)流

新建一個(gè)寫(xiě)入流.
寫(xiě)入的時(shí)候直接使用方法write,參數(shù)為數(shù)據(jù)片段
把readMe.txt里面的內(nèi)容寫(xiě)到writeMe2.txt里面

var fs = require("fs")
var myReadStream = fs.createReadStream(__dirname + "/readMe.txt")
var myWriteStream = fs.createWriteStream(__dirname+"/writeMe2.txt")//新建一個(gè)寫(xiě)入流.
myReadStream.setEncoding("utf8")
var data = ""
myReadStream.on("data",function(chunk) {
    myWriteStream.write(chunk)//寫(xiě)入的時(shí)候直接使用方法write,參數(shù)為數(shù)據(jù)片段
})
myReadStream.on("end",function () {
    // console.log(data)
})

或者:
把"hello world"寫(xiě)入""writeMe2.txt" 文件

var myWriteStream = fs.createWriteStream(__dirname+"/writeMe2.txt")
var writeData = "hello world"
myWriteStream.write(writeData)
myWriteStream.end()
myWriteStream.on("finish",function () {
    console.log("finish")
})

使用管道更方便得實(shí)現(xiàn)流的操作

實(shí)現(xiàn)復(fù)制內(nèi)容的操作

var myReadStream = fs.createReadStream(__dirname + "/readMe.txt")
var myWriteStream = fs.createWriteStream(__dirname+"/writeMe2.txt")
myReadStream.pipe(myWriteStream)

把readMe的內(nèi)容復(fù)制到writeMe2
管道運(yùn)送流

流與管道例子

加密,壓縮的過(guò)程

// 壓縮
var crypto = require("crypto");
var fs = require("fs");
var zlib = require("zlib");

var password = new Buffer(process.env.PASS || "password");
var encryptStream = crypto.createCipher("aes-256-cbc", password);

var gzip = zlib.createGzip();
var readStream = fs.createReadStream(__dirname + "/readMe.txt"); // current file
var writeStream = fs.createWriteStream(__dirname + "/out.gz");

readStream // reads current file
    .pipe(encryptStream) // encrypts
    .pipe(gzip) // compresses
    .pipe(writeStream) // writes to out file
    .on("finish", function() { // all done
        console.log("done");
    });



// 解壓
var crypto = require("crypto");
var fs = require("fs");
var zlib = require("zlib");

var password = new Buffer(process.env.PASS || "password");
var decryptStream = crypto.createDecipher("aes-256-cbc", password);

var gzip = zlib.createGunzip();
var readStream = fs.createReadStream(__dirname + "/out.gz");

readStream // reads current file
    .pipe(gzip) // uncompresses
    .pipe(decryptStream) // decrypts
    .pipe(process.stdout) // writes to terminal
    .on("finish", function() { // finished
        console.log("done");
    });