File System (fs) Module

The Node.js File System module, commonly accessed via require('fs'), provides an extensive API for interacting with the file system. It allows you to read, write, update, delete, and manage files and directories. Here are some key aspects:

Asynchronous vs Synchronous Methods

1️⃣ Asynchronous Methods

Most methods in the fs module are asynchronous, meaning they perform I/O operations without blocking the event loop. They typically use an error-first callback pattern.

const fs = require('fs');

fs.readFile('example.txt', 'utf8', (err, data) => {
  if (err) {
    console.error('Error reading file:', err);
    return;
  }
  console.log('File content:', data);
});

2️⃣ Synchronous Methods

Synchronous versions (e.g., fs.readFileSync) block the event loop until the operation completes. These are generally used during startup or in scripts where blocking behavior is acceptable.

const fs = require('fs');

try {
  const data = fs.readFileSync('example.txt', 'utf8');
  console.log('File content:', data);
} catch (err) {
  console.error('Error reading file:', err);
}

Common File Operations

• Reading Files:
  • Asynchronously: fs.readFile(path, [options], callback)
  • synchronously: fs.readFileSync(path, [options])
• Writing Files:
  • Asynchronously: fs.writeFile(path, data, [options], callback)
  • Synchronously: fs.writeFileSync(path, data, [options])
• Appending to Files:
  • Asynchronously: fs.appendFile(path, data, [options], callback)
  • Synchronously: fs.appendFileSync(path, data, [options])
• Watching Files:

  • Use fs.watch() to monitor changes to files or directories.

    fs.watch('example.txt', (eventType, filename) => {
      console.log(`File ${filename} changed: ${eventType}`);
    });
    

• Working with Directories:
  • Read Contents: fs.readdir(path, callback)
  • Create a directory: fs.mkdir(path, [options], callback)
  • Remove a directory: fs.rmdir(path, [options], callback)