const { spawn } = require('child_process');

const subprocess = spawn('ls');

subprocess.stdout.on('data', (data) => {
  console.log(`Received chunk ${data}`);
});

var spawn = require('child-process-promise').spawn;
 
var promise = spawn('echo', ['hello']);
 
var childProcess = promise.childProcess;
 
console.log('[spawn] childProcess.pid: ', childProcess.pid);
childProcess.stdout.on('data', function (data) {
    console.log('[spawn] stdout: ', data.toString());
});
childProcess.stderr.on('data', function (data) {
    console.log('[spawn] stderr: ', data.toString());
});
 
promise.then(function () {
        console.log('[spawn] done!');
    })
    .catch(function (err) {
        console.error('[spawn] ERROR: ', err);
    });

(async () => {
    let ffmpeg$ = spawnAsync('ffmpeg', ['-i', 'path/to/source.flac', '-codec:a', 'libmp3lame', '-b:a', '320k', '-ar', '44100', 'path/to/output.mp3']);
    let childProcess = ffmpeg$.child;
    childProcess.stdout.on('data', (data) => {
      console.log(`ffmpeg stdout: ${data}`);
    });
    childProcess.stderr.on('data', (data) => {
      console.error(`ffmpeg stderr: ${data}`);
    });
    let result = await ffmpeg$;
    console.log(`ffmpeg pid ${result.pid} exited with code ${result.code}`);
})();
 

const { spawn } = require('child_process');
const subprocess = spawn('bad_command');

subprocess.on('error', (err) => {
  console.error('Failed to start subprocess.');
});

const { spawn } = require('child_process');

const subprocess = spawn(process.argv[0], ['child_program.js'], {
  detached: true,
  stdio: 'ignore'
});

subprocess.unref();