Detailed explanation of node file batch renaming examples

This article mainly introduces the example of the method of batch renaming node files. The editor thinks it is quite good, so I will share it with you now and give it as a reference. Let’s follow the editor to take a look, I hope it can help everyone.

In an actual requirement, a batch of files (such as text, pictures) need to be renamed and numbered according to numbers. I just took this opportunity to get familiar with node's fs file operations and wrote a script to batch modify file names.

Requirements

The following image files currently exist

The file names need to be modified in batches , become a unified prefix name and automatically increase the index. The effect after modification is

The simplest manual operation is to rename files one by one, but in the spirit of DRY(Don' t repeat yourself) principle, it is better to write a node script.

Research

To perform file operations in node, you need to understand the fs module

There are synchronous and asynchronous in the fs module Two ways

Read files

//异步
fs.readFile('test.txt', 'utf-8' (err, data) => {
  if (err) {
    throw err;
  }
  console.log(data);
});

//同步
let data = fs.readFileSync('test.txt');
console.log(data);

Asynchronously read file parameters: file path, encoding method, callback function

Write file

fs.writeFile('test2.txt', 'this is text', { 'flag': 'w' }, err => {
  if (err) {
    throw err;
  }
  console.log('saved');
});

Write file parameters: target file, write content, write form, callback function

flag writing method:

r: read file
w: write file
a: append

Create directory

fs.mkdir('dir', (err) => {
  if (err) {
    throw err;
  }
  console.log('make dir success');
});

dir is the name of the new directory

Read the directory

fs.readdir('dir',(err, files) => {
  if (err) {
    throw err;
  }
  console.log(files);
});

dir is the directory name to read, files is the file or directory name array under the directory

Get file information

fs.stat('test.txt', (err, stats)=> {
  console.log(stats.isFile());     //true
})

Stats method after obtaining file information:

Method	Description
stats.isFile()	Whether it is a file
stats.isDirectory()	Whether it is a directory
stats.isBlockDevice()	Whether it is a block device
stats.isCharacterDevice()	Whether it is a character device
stats.isSymbolicLink()	Whether it is a soft link
stats.isFIFO()	Whether it is a UNIX FIFO command pipeline
stats.isSocket()	Whether to create a read stream for Socket

let stream = fs.createReadStream('test.txt');

Create write stream

let stream = fs.createWriteStreamr('test_copy.txt');

Development

Development ideas:

1. Read the source directory

2. Determine whether the storage directory exists, and create a new directory if it does not exist

3. Copy files

4. Determine whether the copied content is a file

5. Create a read stream

6. Create a write stream

7. Link pipe, write file content

let fs = require('fs'),
  src = 'src',
  dist = 'dist',
  args = process.argv.slice(2),
  filename = 'image',
  index = 0;

//show help
if (args.length === 0 || args[0].match('--help')) {
  console.log('--help\n \t-src 文件源\n \t-dist 文件目标\n \t-n 文件名\n \t-i 文件名索引\n');
  return false;
}

args.forEach((item, i) => {
  if (item.match('-src')) {
    src = args[i + 1];
  } else if (item.match('-dist')) {
    dist = args[i + 1];
  } else if (item.match('-n')) {
    filename = args[i + 1];
  } else if (item.match('-i')) {
    index = args[i + 1];
  }
});

fs.readdir(src, (err, files) => {
  if (err) {
    console.log(err);
  } else {
    fs.exists(dist, exist => {
      if (exist) {
        copyFile(files, src, dist, filename, index);
      } else {
        fs.mkdir(dist, () => {
          copyFile(files, src, dist, filename, index);
        })
      }
    });
  }
});

function copyFile(files, src, dist, filename, index) {
  files.forEach(n => {
    let readStream,
      writeStream,
      arr = n.split('.'),
      oldPath = src + '/' + n,
      newPath = dist + '/' + filename + index + '.' + arr[arr.length - 1];
    fs.stat(oldPath, (err, stats) => {
      if (err) {
        console.log(err);
      } else if (stats.isFile()) {
        readStream = fs.createReadStream(oldPath);
        writeStream = fs.createWriteStream(newPath);
        readStream.pipe(writeStream);
      }
    });
    index++;
  })
}

Effect

Summary

node provides many modules that can help us complete the functional development of different needs, so that javascript is not limited to browsers , trying to write some scripts yourself will help you understand these modules, and it can also improve office efficiency.

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