Node.js: Sistema de Arquivos

const fs = require('fs');

// Synchronize
const data = fs.readFileSync('config.json', 'utf8');

// Asynchronous Callbacks
fs.readFile('config.json', 'utf8', (err, data) => {
  if (err) throw err;
  console.log(data);
});

// Promise
const fsPromises = require('fs/promises');
fsPromises.readFile('config.json', 'utf8')
  .then(data => console.log(data))
  .catch(err => console.error(err));

const fs = require('fs');

console.log('Start Reading...');
const data = fs.readFileSync('big-log.txt', 'utf8');
console.log('Reading complete，Number of lines：', data.split('\n').length);
console.log('This line must wait until the data has finished loading before it is executed.');

Start Reading...
Reading complete，Number of lines：50000
This line must wait until the data has finished loading before it is executed.

const fs = require('fs');

console.log('Start Reading...');
fs.readFile('big-log.txt', 'utf8', (err, data) => {
  if (err) throw err;
  console.log('Reading complete，Number of lines：', data.split('\n').length);
});
console.log('This line is executed immediately，No need to wait for the data to be read');

Start Reading...
This line is executed immediately，No need to wait for the data to be read
Reading complete，Number of lines：50000

const fs = require('fs');

fs.writeFile('output.txt', 'Content on the first line\n', 'utf8', (err) => {
  if (err) throw err;
  console.log('Write complete');

  fs.appendFile('output.txt', 'The second line added\n', 'utf8', (err) => {
    if (err) throw err;
    console.log('Addition Complete');

    fs.readFile('output.txt', 'utf8', (err, data) => {
      if (err) throw err;
      console.log('Document Content：\n', data);
    });
  });
});

Write complete
Addition Complete
Document Content：
 Content on the first line
The second line added

const fs = require('fs/promises');

async function writeAndRead() {
  try {
    await fs.writeFile('output.txt', 'Content on the first line\n', 'utf8');
    console.log('Write complete');
    await fs.appendFile('output.txt', 'The second line added\n', 'utf8');
    console.log('Addition Complete');
    const data = await fs.readFile('output.txt', 'utf8');
    console.log('Document Content：\n', data);
  } catch (err) {
    console.error('Operation Failed：', err.message);
  }
}

writeAndRead();

const fs = require('fs/promises');

async function deleteFile() {
  try {
    await fs.unlink('output.txt');
    console.log('The file has been deleted');
  } catch (err) {
    console.error('Deletion Failed：', err.message);
  }
}

deleteFile();

const fs = require('fs/promises');

async function dirOperations() {
  try {
    await fs.mkdir('logs', { recursive: true });
    console.log('The directory was successfully created');

    await fs.writeFile('logs/app.log', '2025-01-01 Server started\n', 'utf8');
    await fs.writeFile('logs/error.log', '2025-01-01 Connection timeout\n', 'utf8');

    const files = await fs.readdir('logs');
    console.log('Table of Contents：', files);
  } catch (err) {
    console.error('Operation Failed：', err.message);
  }
}

dirOperations();

The directory was successfully created
Table of Contents： [ 'app.log', 'error.log' ]

const fs = require('fs/promises');

async function checkType() {
  const stats = await fs.stat('logs');
  console.log('logs This is the table of contents：', stats.isDirectory());
  console.log('logs It is a file：', stats.isFile());

  const fileStats = await fs.stat('logs/app.log');
  console.log('app.log It is a file：', fileStats.isFile());
  console.log('File size：', fileStats.size, 'bytes');
}

checkType();

logs This is the table of contents： true
logs It is a file： false
app.log It is a file： true
File size： 29 bytes

const fsCallback = require('fs');
const fsPromise = require('fs/promises');

// Error-First Callback
fsCallback.readFile('not-exist.txt', 'utf8', (err, data) => {
  if (err) {
    console.error('Callback Method - Error：', err.code);
    return;
  }
  console.log(data);
});

// Promise Method
async function readWithPromise() {
  try {
    const data = await fsPromise.readFile('not-exist.txt', 'utf8');
    console.log(data);
  } catch (err) {
    console.error('PromiseMethod - Error：', err.code);
  }
}

readWithPromise();

Callback Method - Error： ENOENT
PromiseMethod - Error： ENOENT

const fs = require('fs/promises');

async function readEncodings() {
  await fs.writeFile('sample.txt', 'Hello The World', 'utf8');

  const utf8Data = await fs.readFile('sample.txt', 'utf8');
  console.log('UTF-8：', utf8Data);

  const base64Data = await fs.readFile('sample.txt', 'base64');
  console.log('Base64：', base64Data);

  const bufferData = await fs.readFile('sample.txt');
  console.log('Buffer：', bufferData);
  console.log('Buffer Hexadecimal：', bufferData.toString('hex'));
}

readEncodings();

UTF-8： Hello The World
Base64： SGVsbG8g5LiW55WM
Buffer： <Buffer 48 65 6c 6c 6f 20 e4 b8 96 e7 95 8c>
Buffer Hexadecimal： 48656c6c6f20e4b896e7958c

const fs = require('fs/promises');
const path = require('path');

async function fileManager() {
  const dir = 'project-data';
  const configPath = path.join(dir, 'config.json');
  const logPath = path.join(dir, 'app.log');

  try {
    // Step 1: Create a Directory
    await fs.mkdir(dir, { recursive: true });
    console.log('✓ The table of contents has been created:', dir);

    // Step 2: Write to the configuration file
    const config = {
      appName: 'LogAnalyzer',
      version: '1.0.0',
      maxLines: 50000,
      encoding: 'utf8'
    };
    await fs.writeFile(configPath, JSON.stringify(config, null, 2), 'utf8');
    console.log('✓ The configuration file has been written.:', configPath);

    // Step 3: Read and Parse the Configuration
    const raw = await fs.readFile(configPath, 'utf8');
    const parsed = JSON.parse(raw);
    console.log('✓ Configuration loaded:', parsed.appName, 'v' + parsed.version);

    // Step 4: Add a log entry
    const timestamp = new Date().toISOString();
    await fs.appendFile(logPath, `[${timestamp}] Service started\n`, 'utf8');
    await fs.appendFile(logPath, `[${timestamp}] Config loaded: ${parsed.maxLines} lines\n`, 'utf8');
    console.log('✓ The log has been appended.:', logPath);

    // Step 5: List the contents of the table of contents
    const entries = await fs.readdir(dir, { withFileTypes: true });
    console.log('✓ Table of Contents:');
    for (const entry of entries) {
      const type = entry.isDirectory() ? '[DIR]' : '[FILE]';
      const stats = await fs.stat(path.join(dir, entry.name));
      console.log(`  ${type} ${entry.name} (${stats.size} bytes)`);
    }
  } catch (err) {
    console.error('✗ Operation Failed:', err.message);
  }
}

fileManager();

✓ The table of contents has been created: project-data
✓ The configuration file has been written.: project-data/config.json
✓ Configuration loaded: LogAnalyzer v1.0.0
✓ The log has been appended.: project-data/app.log
✓ Table of Contents:
  [FILE] app.log (106 bytes)
  [FILE] config.json (98 bytes)