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The fs Module

Reading, writing, deleting files and working with directories using the fs module.

File System Module

The fs (file system) module provides an API for interacting with the file system in a POSIX-like manner.

const fs = require('fs');\n\n// Synchronous - blocking\nconst data = fs.readFileSync('./file.txt', 'utf8');\nconsole.log(data);\n\n// Asynchronous - non-blocking (callback)\nfs.readFile('./file.txt', 'utf8', (err, data) => {\n  if (err) throw err;\n  console.log(data);\n});\n\n// Promise based (fs.promises)\nconst fsPromises = require('fs').promises;\n\nasync function readFile() {\n  try {\n    const data = await fsPromises.readFile('./file.txt', 'utf8');\n    console.log(data);\n  } catch (err) {\n    console.error(err);\n  }\n}

Writing Files

// Write (overwrites)\nfs.writeFileSync('output.txt', 'Hello World');\n\n// Append\nfs.appendFileSync('log.txt', 'New log entry\n');\n\n// Directory operations\nfs.mkdirSync('./data', { recursive: true });\nfs.readdirSync('./folder');\nfs.rmSync('./old-file.txt');

Examples

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

const dir = './logs';
if (!fs.existsSync(dir)) {
  fs.mkdirSync(dir, { recursive: true });
}

const logFile = path.join(dir, 'app.log');
fs.appendFileSync(logFile, `${new Date().toISOString()} - Started\n`);

console.log('Log entry written to', logFile);
console.log('Directory contents:', fs.readdirSync(dir));

Table of Contents

Related Lessons

The fs Module

File System Module

Writing Files

Examples

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