Jassif Team Institution

CommonJS (Node.js இல் இயல்புநிலை)

const fs = require('fs');

ES Modules (Node.js 14+ with "type": "module" in package.json)

import fs from 'fs';
// Or for specific methods:
// import { readFile, writeFile } from 'fs/promises';

// Using promises (Node.js 10.0.0+)
const fs = require('fs').promises;

// Or with destructuring
const { readFile, writeFile } = require('fs').promises;

// Or with ES modules
// import { readFile, writeFile } from 'fs/promises';

myfile.txt

This is the content of myfile.txt

எடுத்துக்காட்டு: Callbacks உடன் கோப்பைப் படித்தல்

const fs = require('fs');

// Read file asynchronously with callback
fs.readFile('myfile.txt', 'utf8', (err, data) => {
  if (err) {
    console.error('Error reading file:', err);
    return;
  }
  console.log('File content:', data);
});

// For binary data (like images), omit the encoding
fs.readFile('image.png', (err, data) => {
  if (err) throw err;
  // data is a Buffer containing the file content
  console.log('Image size:', data.length, 'bytes');
});

எடுத்துக்காட்டு: async/await உடன் கோப்பைப் படித்தல்

// Using fs.promises (Node.js 10.0.0+)
const fs = require('fs').promises;

async function readFileExample() {
  try {
    const data = await fs.readFile('myfile.txt', 'utf8');
    console.log('File content:', data);
  } catch (err) {
    console.error('Error reading file:', err);
  }
}

readFileExample();

// Or with util.promisify (Node.js 8.0.0+)
const { promisify } = require('util');
const readFileAsync = promisify(require('fs').readFile);

async function readWithPromisify() {
  try {
    const data = await readFileAsync('myfile.txt', 'utf8');
    console.log(data);
  } catch (err) {
    console.error(err);
  }
}

readWithPromisify();

எடுத்துக்காட்டு: ஒத்திசைவாக கோப்பைப் படித்தல்

const fs = require('fs');

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

எடுத்துக்காட்டு: கோப்பில் எழுதுதல்

const fs = require('fs').promises;

async function writeFileExample() {
  try {
    // Write text to a file
    await fs.writeFile('myfile.txt', 'Hello, World!', 'utf8');

    // Write JSON data
    const data = { name: 'John', age: 30, city: 'New York' };
    await fs.writeFile('data.json', JSON.stringify(data, null, 2), 'utf8');

    console.log('Files created successfully');
  } catch (err) {
    console.error('Error writing files:', err);
  }
}

writeFileExample();

எடுத்துக்காட்டு: கோப்பில் சேர்த்தல்

const fs = require('fs').promises;

async function appendToFile() {
  try {
    // Append a timestamped log entry
    const logEntry = `${new Date().toISOString()}: Application started\n`;
    await fs.appendFile('app.log', logEntry, 'utf8');

    console.log('Log entry added');
  } catch (err) {
    console.error('Error appending to file:', err);
  }
}

appendToFile();

எடுத்துக்காட்டு: கோப்பு கைப்பிடிகளைப் பயன்படுத்துதல்

const fs = require('fs').promises;

async function writeWithFileHandle() {
  let fileHandle;

  try {
    // Open a file for writing (creates if doesn't exist)
    fileHandle = await fs.open('output.txt', 'w');

    // Write content to the file
    await fileHandle.write('First line\n');
    await fileHandle.write('Second line\n');
    await fileHandle.write('Third line\n');

    console.log('Content written successfully');
  } catch (err) {
    console.error('Error writing to file:', err);
  } finally {
    // Always close the file handle
    if (fileHandle) {
      await fileHandle.close();
    }
  }
}

writeWithFileHandle();

எடுத்துக்காட்டு: ஸ்ட்ரீம்களுடன் பெரிய கோப்புகளை எழுதுதல்

const fs = require('fs');
const { pipeline } = require('stream/promises');
const { Readable } = require('stream');

async function writeLargeFile() {
  // Create a readable stream (could be from HTTP request, etc.)
  const data = Array(1000).fill().map((_, i) => `Line ${i + 1}: ${'x'.repeat(100)}\n`);
  const readable = Readable.from(data);

  // Create a writable stream to a file
  const writable = fs.createWriteStream('large-file.txt');

  try {
    // Pipe the data from readable to writable
    await pipeline(readable, writable);
    console.log('Large file written successfully');
  } catch (err) {
    console.error('Error writing file:', err);
  }
}

writeLargeFile();

எடுத்துக்காட்டு: கோப்பை நீக்குதல்

const fs = require('fs').promises;

async function deleteFile() {
  const filePath = 'file-to-delete.txt';

  try {
    // Check if file exists before deleting
    await fs.access(filePath);

    // Delete the file
    await fs.unlink(filePath);
    console.log('File deleted successfully');
  } catch (err) {
    if (err.code === 'ENOENT') {
      console.log('File does not exist');
    } else {
      console.error('Error deleting file:', err);
    }
  }
}

deleteFile();

எடுத்துக்காட்டு: பல கோப்புகளை நீக்குதல்

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

async function deleteFiles() {
  const filesToDelete = [
    'temp1.txt',
    'temp2.txt',
    'temp3.txt'
  ];

  try {
    // Delete all files in parallel
    await Promise.all(
      filesToDelete.map(file =>
        fs.unlink(file).catch(err => {
          if (err.code !== 'ENOENT') {
            console.error(`Error deleting ${file}:`, err);
          }
        })
      )
    );

    console.log('Files deleted successfully');
  } catch (err) {
    console.error('Error during file deletion:', err);
  }
}

deleteFiles();

எடுத்துக்காட்டு: அடைவுகளை நீக்குதல்

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

async function deleteDirectory(dirPath) {
  try {
    // Check if the directory exists
    const stats = await fs.stat(dirPath);
   
    if (!stats.isDirectory()) {
      console.log('Path is not a directory');
      return;
    }

    // For Node.js 14.14.0+ (recommended)
    await fs.rm(dirPath, { recursive: true, force: true });

    // For older Node.js versions (deprecated but still works)
    // await fs.rmdir(dirPath, { recursive: true });

    console.log('Directory deleted successfully');
  } catch (err) {
    if (err.code === 'ENOENT') {
      console.log('Directory does not exist');
    } else {
      console.error('Error deleting directory:', err);
    }
  }
}

// Usage
deleteDirectory('directory-to-delete');

எடுத்துக்காட்டு: அடைவை காலியாக்குதல்

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

async function emptyDirectory(dirPath) {
  try {
    // Read the directory
    const files = await fs.readdir(dirPath, { withFileTypes: true });

    // Delete all files and directories in parallel
    await Promise.all(
      files.map(file => {
        const fullPath = path.join(dirPath, file.name);
        return file.isDirectory()
          ? fs.rm(fullPath, { recursive: true, force: true })
          : fs.unlink(fullPath);
      })
    );

    console.log('Directory emptied successfully');
  } catch (err) {
    console.error('Error emptying directory:', err);
  }
}

// Usage
emptyDirectory('directory-to-empty');

எடுத்துக்காட்டு: கோப்பை மறுபெயரிடுதல்

const fs = require('fs').promises;

async function renameFile() {
  const oldPath = 'old-name.txt';
  const newPath = 'new-name.txt';

  try {
    // Check if source file exists
    await fs.access(oldPath);

    // Check if destination file already exists
    try {
      await fs.access(newPath);
      console.log('Destination file already exists');
      return;
    } catch (err) {
      // Destination doesn't exist, safe to proceed
    }

    // Perform the rename
    await fs.rename(oldPath, newPath);
    console.log('File renamed successfully');
  } catch (err) {
    if (err.code === 'ENOENT') {
      console.log('Source file does not exist');
    } else {
      console.error('Error renaming file:', err);
    }
  }
}

// Usage
renameFile();

எடுத்துக்காட்டு: கோப்பை வெவ்வேறு அடைவுக்கு நகர்த்துதல்

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

async function moveFile() {
  const sourceFile = 'source/file.txt';
  const targetDir = 'destination';
  const targetFile = path.join(targetDir, 'file.txt');

  try {
    // Ensure source file exists
    await fs.access(sourceFile);

    // Create target directory if it doesn't exist
    await fs.mkdir(targetDir, { recursive: true });

    // Move the file
    await fs.rename(sourceFile, targetFile);

    console.log('File moved successfully');
  } catch (err) {
    if (err.code === 'ENOENT') {
      console.log('Source file does not exist');
    } else if (err.code === 'EXDEV') {
      console.log('Cross-device move detected, using copy+delete fallback');
      await moveAcrossDevices(sourceFile, targetFile);
    } else {
      console.error('Error moving file:', err);
    }
  }
}

// Helper function for cross-device moves
async function moveAcrossDevices(source, target) {
  try {
    // Copy the file
    await fs.copyFile(source, target);

    // Delete the original
    await fs.unlink(source);

    console.log('File moved across devices successfully');
  } catch (err) {
    // Clean up if something went wrong
    try { await fs.unlink(target); } catch (e) {}
    throw err;
  }
}

// Usage
moveFile();

எடுத்துக்காட்டு: தொகுதி மறுபெயரிடுதல் கோப்புகள்

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

async function batchRename() {
  const directory = 'images';
  const pattern = /^image(\d+)\.jpg$/;

  try {
    // Read directory contents
    const files = await fs.readdir(directory);

    // Process each file
    for (const file of files) {
      const match = file.match(pattern);
      if (match) {
        const [_, number] = match;
        const newName = `photo-${number.padStart(3, '0')}.jpg`;
        const oldPath = path.join(directory, file);
        const newPath = path.join(directory, newName);

        // Skip if the new name is the same as the old name
        if (oldPath !== newPath) {
          await fs.rename(oldPath, newPath);
          console.log(`Renamed: ${file} - ${newName}`);
        }
      }
    }

    console.log('Batch rename completed');
  } catch (err) {
    console.error('Error during batch rename:', err);
  }
}

batchRename();

எடுத்துக்காட்டு: அணு கோப்பு புதுப்பிப்பு

const fs = require('fs').promises;
const path = require('path');
const os = require('os');

async function updateFileAtomic(filePath, newContent) {
  const tempPath = path.join(
    os.tmpdir(),
    `temp-${Date.now()}-${Math.random().toString(36).substr(2, 9)}`
  );

  try {
    // 1. Write to temp file
    await fs.writeFile(tempPath, newContent, 'utf8');

    // 2. Verify the temp file was written correctly
    const stats = await fs.stat(tempPath);
    if (stats.size === 0) {
      throw new Error('Temporary file is empty');
    }

    // 3. Rename (atomic on most systems)
    await fs.rename(tempPath, filePath);

    console.log('File updated atomically');
  } catch (err) {
    // Clean up temp file if it exists
    try { await fs.unlink(tempPath); } catch (e) {}

    console.error('Atomic update failed:', err);
    throw err;
  }
}

// Usage
updateFileAtomic('important-config.json', JSON.stringify({ key: 'value' }, null, 2));