fs Module

fileDescriptor.js

const fs = require('fs');

module.exports.loadHome = (req, res) => {
  res.render('index', {title: 'fs Module Node.js', message: 'File System Module Tutorial'});
};

module.exports.getfd = (req, res) => {
  fs.open(__dirname + '/files/TestFile1.txt', 'r', (err, fd) => {
    if(err){
      return res.render('index', {title: 'Error', message: 'There was an error opening the file', content: err});
    }
    //You can now use fd to read, write or get stats about the file
    fs.readFile(fd, (err, data) => {
      if(err){
        return res.render('index', {title: 'Error', message: 'There was an error reading the file', content: err});
      }
      
      //Always close the file descriptor as this may lead to memory leaks
      fs.close(fd, (err) => {
        if(err){
          return res.render('index', {title: 'Error', message: 'There was an error closing the file', content: err});
        }
      });

      res.render('index', {title: 'fs Module Node.js', message: 'File Descriptor for the file is ' + fd, content: data});
    });
  });
}

fsReadStream.js

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

let pathToFile = path.join(__dirname, '../files/', 'TestFile1.txt');

let readStream = fs.createReadStream(pathToFile);

readStream.on('open', (fd) => {
  console.log('Stream opened');
});

readStream.on('data', (chunk) => {
  console.log(`Data chunk is ${chunk}`);
});

readStream.on('close', () => {
  console.log('Stream closed');
});

fsStats.js

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

fs.open(path.join(__dirname, '../files/', 'TestFile1.txt'), 'r', (err, fd) => {

  if(err){
    console.log('Error opening file');
    console.log(err);
  }

  let stats = fs.fstat(fd, (err, stats) => {
    if(err){
      console.log('Error finding stats');
    }
    
    console.log(stats);

    fs.close(fd, (err) => {
      if(err){
        console.log('Error closing file');
      }
    })
  });

});

fsWatch.js

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

let pathToFile = path.join(__dirname, '../files/', 'TestFile1.txt');

let watcher = fs.watch(pathToFile, (eventType, filename) => {
  console.log(`Event type is ${eventType}`);        //This can either be change or rename
  if(filename){
    console.log(`Filename is ${filename}`);         //This may not always be set depending on the OS
  }
});

setTimeout(() => {
  console.log('Closing watcher');
  watcher.close();
}, 5000);

fsWriteStream.js

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

let pathToFile = path.join(__dirname, '../files/', 'TestFile2.txt');

let writeStream = fs.createWriteStream(pathToFile);

writeStream.on('open', (fd) => {
  console.log('Stream opened');
  writeStream.write('THis is some extra text', (err) => {
    if(err){
      console.log('Error writing data');
    }
    console.log('Data written');
  });
});


writeStream.on('finish', () => {
  console.log('Write complete');
});

Stats.js

Stats {
  dev: 2114,
  ino: 48064969,
  mode: 33188,
  nlink: 1,
  uid: 85,
  gid: 100,
  rdev: 0,
  size: 527,
  blksize: 4096,
  blocks: 8,
  atimeMs: 1318289051000.1,
  mtimeMs: 1318289051000.1,
  ctimeMs: 1318289051000.1,
  birthtimeMs: 1318289051000.1,
  atime: Mon, 10 Oct 2011 23:24:11 GMT,
  mtime: Mon, 10 Oct 2011 23:24:11 GMT,
  ctime: Mon, 10 Oct 2011 23:24:11 GMT,
  birthtime: Mon, 10 Oct 2011 23:24:11 GMT }