Modules fs in node js

Understanding the fs Module in Node.js

The fs module in Node.js is a built-in module that provides an API for interacting with the file system. It allows you to perform various operations like reading, writing, updating, and deleting files and directories.

Key Features of the fs Module

• Reading Files: Read the content of a file.
• Writing Files: Write data to a file.
• Appending Files: Append data to an existing file.
• Deleting Files: Remove files from the system.
• Directory Operations: Create, read, and delete directories.

Installation with npm

In earlier versions of Node.js, you would typically install modules via npm, including built-in ones like fs. However, fs is a core module, so you don't need to install it separately. The command npm install fs --save is outdated for fs as it’s already included in Node.js by default.

Example 1: Reading a File

Let's start with reading a file using the fs module.

Code:

const fs = require('fs');

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

Explanation:

• fs.readFile reads the content of the file asynchronously.
• 'example.txt' is the file you want to read.
• 'utf8' specifies the encoding.
• The callback function receives an error object err (if any) and the file content data.

Output:

If the file example.txt contains:

Hello, Node.js!

The output in the console will be:

File content: Hello, Node.js!

Example 2: Writing to a File

Next, let’s write some data to a file.

Code:

const fs = require('fs');

// Writing to a file asynchronously
fs.writeFile('output.txt', 'Hello, Node.js!', 'utf8', (err) => {
    if (err) {
        console.error('Error writing to the file:', err);
        return;
    }
    console.log('File has been written successfully!');
});

Explanation:

• fs.writeFile writes data to a file asynchronously.
• 'output.txt' is the file where the content will be written.
• 'Hello, Node.js!' is the content to be written.
• 'utf8' specifies the encoding.

Output:

A file named output.txt will be created with the content:

Hello, Node.js!

Console output:

File has been written successfully!

Example 3: Appending to a File

Appending data to an existing file is also straightforward.

Code:

const fs = require('fs');

// Appending to a file asynchronously
fs.appendFile('output.txt', '\nThis is additional content.', 'utf8', (err) => {
    if (err) {
        console.error('Error appending to the file:', err);
        return;
    }
    console.log('Content has been appended successfully!');
});

Explanation:

• fs.appendFile adds data to an existing file.
• The content \nThis is additional content. will be added at the end of the file output.txt.

Output:

If output.txt initially contained:

Hello, Node.js!

After running the code, it will contain:

Hello, Node.js!
This is additional content.

Console output:

Content has been appended successfully!

Example 4: Deleting a File

Deleting a file is just as easy.

Code:

const fs = require('fs');

// Deleting a file asynchronously
fs.unlink('output.txt', (err) => {
    if (err) {
        console.error('Error deleting the file:', err);
        return;
    }
    console.log('File has been deleted successfully!');
});

Explanation:

• fs.unlink is used to delete a file.
• 'output.txt' is the file to be deleted.

Output:

If output.txt exists, it will be deleted, and the console will show:

File has been deleted successfully!

Example 5: Working with Directories

You can also create and remove directories using the fs module.

Creating a Directory:

const fs = require('fs');

// Creating a new directory
fs.mkdir('new_directory', { recursive: true }, (err) => {
    if (err) {
        console.error('Error creating directory:', err);
        return;
    }
    console.log('Directory created successfully!');
});

Deleting a Directory:

const fs = require('fs');

// Deleting a directory
fs.rmdir('new_directory', { recursive: true }, (err) => {
    if (err) {
        console.error('Error deleting directory:', err);
        return;
    }
    console.log('Directory deleted successfully!');
});

Conclusion

The fs module is powerful and essential for file system operations in Node.js. With it, you can easily manage files and directories within your application. Remember, since fs is a core module, there’s no need to install it separately using npm.