const fs = require('fs');

fs.appendFile('./message.txt', 'Hello content!\n', function (err) {

if (err) throw err;

console.log('Saved!');

});

fs.readFile("./message.txt", (err, data) => {

console.log(data.toString());

console.log("Done with read");

})

fs.unlink('./message.txt',function (err) {

if (err) throw err;

console.log('Saved!');

});

const cp = require('child_process');

const ls = cp.spawn('ls', ['-lh', '/home/archit/Desktop']);

ls.stdout.on('data', (data) => {

console.log(`stdout: ${data}`);

});

cp.exec('dir | find /c /v ""', (error, stdout, stderr) => {

if (error) {

console.error(`exec error: ${error}`);

return;

}

console.log(`stdout: No. of directories = ${stdout}`);

if (stderr!= "")

console.error(`stderr: ${stderr}`);

});

const child = cp.execFile('node', ['runner.js'],

(error, stdout, stderr) => {

if (error) {

throw error;

}

console.log(stdout);

});

var events = require('events');

var eventEmitter = new events.EventEmitter();

var myEventHandler = (a)=> {

setTimeout(() => {

console.log(`this happens asynchronously${a}`);

},1000);

console.log("before **");

}

eventEmitter.on('scream', myEventHandler);

eventEmitter.emit('scream', '!!');

console.log("between **");

const { Worker } = require('worker_threads')

function runService(workerData) {

return new Promise((resolve, reject) => {

const worker = new Worker(

'./worker.js', { workerData });

worker.on('message', resolve);

worker.on('error', reject);

worker.on('exit', (code) => {

if (code !== 0)

reject(new Error(

`Stopped the Worker Thread with the exit code: ${code}`));

})

})

}

async function run() {

const result = await runService('Archit')

console.log(result);

}

run().catch(err => console.error(err))

console.log("worker threads implementation")