const fs = require('fs');

// Create a readable stream in chunks inside buffer
// HighWaterMark => the size of a chunck
let readable = fs.createReadStream(_dirname + '/path.txt', 
                         { encoding: 'utf8', highWaterMark: 32 * 1024 });

// Writable stream
let writable = fs.createWriteStream(_dirname + '/pathCopy.txt');

// Stream is an event emitter 
readable.on('data', chunk => {
    writable.write(chunk);
})