1. Writing Files

---

1.1 Asynchronous writeFile

const fs = require('fs');

fs.writeFile('./motto.txt', 'When three walk together, one can be my teacher.', err => {
  if (err) {
    console.error(err);
    return;
  }
  console.log('File written');
});

1.2 Synchronous writeFileSync

try {
  fs.writeFileSync('./motto.txt', 'When three walk together, one can be my teacher.');
} catch (e) {
  console.error(e);
}

1.3 Apending Data

// async append
fs.appendFile('./motto.txt', '\nChoose the good and follow it, correct the bad.', err => {
  if (err) throw err;
  console.log('Appended');
});

// sync append
fs.appendFileSync('./motto.txt', '\nReview the old to know the new.');

1.4 Streaming Writes with createWriteStream

const ws = fs.createWriteStream('./poem.txt');

ws.write('A square pond like a mirror unfolds,\r\n');
ws.write('Clouds and light wander together.\r\n');
ws.write('Why is the water so clear?\r\n');
ws.write('Because fresh springs keep flowing.\r\n');
ws.end();

2. Reading Files

---

2.1 Asynchronous readFile

fs.readFile('./motto.txt', 'utf8', (err, data) => {
  if (err) throw err;
  console.log(data);
});

2.2 Synchronous readFileSync

const buffer = fs.readFileSync('./motto.txt');
const text   = fs.readFileSync('./motto.txt', 'utf8');

2.3 Streaming Reads with createReadStream

const rs = fs.createReadStream('./poem.txt');

rs.on('data', chunk => {
  console.log(chunk.toString());
});

rs.on('end', () => {
  console.log('Read finished');
});

3. Copy, Move, and Rename

---

3.1 Copying Files

// memory-heavy approach
const data = fs.readFileSync('./movie.mp4');
fs.writeFileSync('./movie-copy.mp4', data);

// stream approach
const rs = fs.createReadStream('./movie.mp4');
const ws = fs.createWriteStream('./movie-copy2.mp4');
rs.pipe(ws);

3.2 Move / Rename

fs.rename('./poem.txt', './short-poem.txt', err => {
  if (err) throw err;
  console.log('Renamed');
});

fs.renameSync('./motto.txt', './my-motto.txt');

4. Deleting Files

---

fs.unlink('./temp.log', err => {
  if (err) throw err;
  console.log('Deleted');
});

fs.unlinkSync('./old.db');

5. Diretcory Operations

---

5.1 Creating Directories

// single
fs.mkdir('./docs', err => {
  if (err) throw err;
});

// nested
fs.mkdir('./a/b/c', { recursive: true }, err => {
  if (err) throw err;
});

fs.mkdirSync('./x/y/z', { recursive: true });

5.2 Reading Directories

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

const list = fs.readdirSync('./x');

5.3 Removing Directories

fs.rmdir('./docs', err => {
  if (err) throw err;
});

fs.rmdir('./a', { recursive: true }, err => {
  if (err) throw err;
});

fs.rmdirSync('./x', { recursive: true });

6. Inspecting File Stats

---

fs.stat('./my-motto.txt', (err, stats) => {
  if (err) throw err;
  console.log(stats);
  console.log('Is file?', stats.isFile());
  console.log('Size (bytes):', stats.size);
});

const info = fs.statSync('./my-motto.txt');

7. Path Handling

---

Relative paths are resolved against the process working directory, not the script loaction. To avoid surprises, always build absolute paths with __dirname:

const path = require('path');
const data = fs.readFileSync(path.join(__dirname, 'data.txt'));