05_ Node JS file management module FS

One 、fs Basic method ：

• fs.stat Check whether it's a file or a directory .
• fs.mkdir Create directory .
• fs.writeFile Create write file .
• fs.appendFile Additional documents .
• fs.readFile Read the file （ asynchronous ）.
• fs.readFileSync Read the file （ Sync ）.
• fs.readdir Read directory .
• fs.rename rename .
• fs.rmdir Delete directory .
• fs.unlink Delete file .

1、fs.stat： Check whether it's a file or a directory

fs.js

const fs = require("fs");
fs.stat('fs.js', (error, stats) => {
    if (error) {
        console.log(error);
        return false;
    } else {
        console.log(stats);
        console.log(` file ：${stats.isFile()}`); //  file ：true
        console.log(` Catalog ：${stats.isDirectory()}`); //  Catalog ：false

        return false;
    };
});
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perform node fs.js.

console.log(stats)：
{ dev: 636204,
  mode: 33206,
  nlink: 1,
  uid: 0,
  gid: 0,
  rdev: 0,
  blksize: undefined,
  ino: 1407374883609714,
  size: 242,
  blocks: undefined,
  atime: 2018-12-25T09:14:40.866Z,
  mtime: 2019-01-15T09:18:06.561Z,
  ctime: 2019-01-15T09:18:06.561Z,
  birthtime: 2018-12-25T09:14:40.866Z }

console.log(` file ：${stats.isFile()}`); //  file ：true
console.log(` Catalog ：${stats.isDirectory()}`); //  Catalog ：false
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Add ：

• stats.isFile() If it's a file return true, Otherwise return to false.
• stats.isDirectory() If it's a directory return true, Otherwise return to false.
• stats.isBlockDevice() If it's block device return true, Otherwise return to false.
• stats.isCharacterDevice() If it's character device return true, Otherwise return to false.
• stats.isSymbolicLink() If it's a soft link back true, Otherwise return to false.
• stats.isFIFO() If it is FIFO, return true, Otherwise return to false,FIFO yes UNIX A special type of command pipeline in .
• stats.isSocket() If it is Socket return true, Otherwise return to false.

2、fs.mkdir： Create directory

fs.js

const fs = require("fs");
fs.mkdir('images', (err) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(" Directory created successfully ！");
    };
});
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Receiving parameters ：

• path： Directory path to be created .
• mode： The directory permissions （ read-write permission ）, Default 0777.
• callback： Callback , Pass exception parameters err.

perform node fs.js.

You'll find one more in the directory images Folder .

3、fs.rmdir： Delete directory

fs.js

const fs = require("fs");
fs.rmdir('images', (err) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(" Directory deleted successfully ！");
    };
});
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perform node fs.js.

You will find the directory images Folder deleted .

4、fs.writeFile： Create write file

fs.js

const fs = require("fs");
fs.writeFile("index.js", "hello NodeJS！", (err) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(" File written successfully ！");
    };
});
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Receiving parameters ：

• filename (String) File name .
• data (String | Buffer) What will be written , It can be a string or buffer data .
• encoding (String) Optional . Default ‘utf-8’, When data yes buffer when , The value should be ignored.
• mode (Number) File read and write permissions , Default 438.
• flag (String) The default value is ‘w’.
• callback { Function } Callback , Pass an exception parameter err.

perform node fs.js.

You'll find one more in the directory index.js Folder , And added “hello NodeJS！” The content of .

Be careful , Such writes , Is to clear all data in the original file , Then add “hello NodeJS！” this sentence , namely ： Existence is coverage , Create... If it doesn't exist .

5、fs.unlink： Delete file

fs.js

const fs = require("fs");
fs.unlink("index.js", (err) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(" Delete successful ！");
    };
});
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perform node fs.js.

You will find the directory index.js File deleted .

6、fs.appendFile： Additional documents

fs.js

const fs = require("fs");
fs.appendFile("index.js", " Additional content ", (err) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(" Append succeeded ！");
    };
});
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perform node fs.js.

You will find the directory index.js A paragraph was appended to the document “ Additional content ”.

7、fs.readFile： Read the file

fs.js

const fs = require("fs");
fs.readFile("index.js", (err, data) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(" Read file successful ！");
        console.log(data); // <Buffer 68 65 6c 6c 6f 20 4e 6f 64 65 4a 53 ef bc 81 e8 bf bd e5 8a a0 e7 9a 84 e5 86 85 e5 ae b9>
    };
});
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perform node fs.js.

console.log(data) Print the results ：

<Buffer 68 65 6c 6c 6f 20 4e 6f 64 65 4a 53 ef bc 81 e8 bf bd e5 8a a0 e7 9a 84 e5 86 85 e5 ae b9>
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8、fs.readdir： Read directory

fs.js

const fs = require("fs");
fs.readdir("node_modules", (err, data) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(" Reading directory succeeded ！");
        console.log(data); // [ '03_tool_multiply.js', 'my_module' ]
    };
});
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perform node fs.js.

console.log(data) Print the results ：

[ '03_tool_multiply.js', 'my_module' ]
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9、fs.rename： rename

fs.js

const fs = require("fs");
fs.rename("index.js", "new_index.js", (err) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(" Rename successful ！");
    };
});
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perform node fs.js.

You will find the directory index.js The file was modified to new_index.js.

10、 Add ：fs.rename You can also cut

fs.js

const fs = require("fs");
fs.rename("new_index.js", "node_modules/new_index.js", (err) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(" Cut successfully ！");
    };
});
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perform node fs.js.

You will find the directory new_index.js The file was moved to node_modules Under the table of contents .

Two 、fs Case study

1、 To determine if there is upload Catalog

fsDemo.js

const fs = require("fs");
fs.stat("upload", (err, stats) => {
    if (err) {
        //  without , establish  upload  Catalog 
        fs.mkdir("upload", (err) => {
            if (err) {
                console.log(err);
                return false;
            } else {
                console.log(" Create success ！");
            };
        })
    } else {
        console.log(stats.isDirectory()); // true
        console.log(" Yes  upload  Catalog , You can do more ！");
    };
});
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perform fsDemo.js.

Print the results ：

console.log(stats.isDirectory()); // true
 Yes  upload  Catalog , You can do more ！
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2、 Read all the files in the directory

fsDemo.js

const fs = require("fs");
fs.readdir("../05fs/", (err, files) => {
    if (err) {
        console.log(err);
        return false;
    } else {
        console.log(files);
        let filesArr = [];

        (function getFile(i) {
            //  The loop ends 
            if (i == files.length) {
                //  Print out all directories 
                console.log(" Catalog ");
                console.log(filesArr);
                return false;
            };

            //  Determine whether the directory is a file or a folder 
            fs.stat("../05fs/" + files[i], (err, stats) => {
                if (stats.isDirectory()) {
                    filesArr.push(files[i]);
                };
                //  Recursively call 
                getFile(i + 1);
            });
        })(0);
    };
});
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perform fsDemo.js.

Print the results ：

[ 'fs.js', 'fsDemo.js', 'fsStream.js', 'upload' ]
 Catalog 
[ 'upload' ]
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3、 ... and 、fs flow

1、fs Stream and its reading

First create a index.js file , And add test text .

fsStream.js

const fs = require("fs");
//  Read files by stream 
const fileReadStream = fs.createReadStream("index.js");
//  Number of reads 
let count = 0;
//  Save the data 
let str = "";
//  Start reading 
fileReadStream.on("data", (chunk) => {
    console.log(`${++count}  Received ：${chunk.length}`);
    str += chunk;
});
//  Read complete 
fileReadStream.on("end", () => {
    console.log(" end ");
    console.log(count);
    console.log(str);
});
//  Read failed 
fileReadStream.on("err", (err) => {
    console.log(err);
});
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perform fsStream.js.

Print the results ：

1  Received ：18
 end 
1
fs  Stream and its reading 
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2、 Write to stream

fsStream.js

const fs = require("fs");
let data = " In the data ...";
//  Create a writable stream , Write to  index.js
let fileWriteStream = fs.createWriteStream("index.js");
//  Start writing 
fileWriteStream.write(data, "utf8");
//  Write completion 
fileWriteStream.end();
fileWriteStream.on("finish", () => {
    console.log(" Write completion ！");
});
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perform fsStream.js.

open index.js file , I found that the content inside turned into “ In the data …”.

Print the results ：

 Write completion ！
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Above, we read and write through the stream .

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