How to Read File Synchronously in Node.js with fs.readFileSync

In Node.js, you can read a file synchronously using the fs.readFileSync method from the built-in fs module. This method blocks the program until the file is fully read and returns its content as a string or buffer.

Syntax

The fs.readFileSync method reads a file synchronously and returns its content. It takes two main arguments:

• path: The file path as a string.
• options (optional): An object or string specifying the encoding (like 'utf8') or other flags.

If encoding is specified, the method returns a string; otherwise, it returns a buffer.

javascript

const fs = require('fs');

const data = fs.readFileSync(path, options);

Example

This example reads a text file named example.txt synchronously and prints its content to the console. It uses UTF-8 encoding to get a readable string.

javascript

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.message);
}

Output

File content: Hello, this is example text.

Common Pitfalls

Reading files synchronously blocks the entire program until the file is read, which can slow down your app if the file is large or the operation is frequent.

Also, forgetting to handle errors can crash your program if the file does not exist or is inaccessible.

Always use try...catch to handle errors when using fs.readFileSync.

javascript

const fs = require('fs');

// Wrong: no error handling
const data = fs.readFileSync('missing.txt', 'utf8');
console.log(data);

// Right: with error handling
try {
  const data = fs.readFileSync('missing.txt', 'utf8');
  console.log(data);
} catch (err) {
  console.error('File not found or cannot be read:', err.message);
}

Quick Reference

Remember these key points when using fs.readFileSync:

• Use utf8 encoding to get a string output.
• Wrap calls in try...catch to handle errors safely.
• Use synchronous reading only for small files or scripts where blocking is acceptable.

Key Takeaways

Use fs.readFileSync(path, encoding) to read files synchronously in Node.js.

Always handle errors with try...catch to avoid crashes.

Synchronous reading blocks the program; avoid it in performance-critical code.

Specify encoding like 'utf8' to get string output instead of a buffer.

Use synchronous reading mainly for small files or simple scripts.