Sometimes, we want to spawn child process and get terminal output live with Node.js.

In this article, we’ll look at how to spawn child process and get terminal output live with Node.js.

How to spawn child process and get terminal output live with Node.js?

To spawn child process and get terminal output live with Node.js, we can use the child_process module’s spawn method.

For instance, we write

const spawn = require('child_process').spawn;
const child = spawn('node ./commands/server.js');
let scriptOutput = "";

child.stdout.setEncoding('utf8');
child.stdout.on('data', (data) => {
  console.log('stdout: ' + data);
  data = data.toString();
  scriptOutput += data;
});

child.stderr.setEncoding('utf8');
child.stderr.on('data', (data) => {
  console.log('stderr: ' + data);
  data = data.toString();
  scriptOutput += data;
});

child.on('close', (code) => {
  console.log('closing code: ' + code);
  console.log('Full output of script: ', scriptOutput);
});

to call spawn to run 'node ./commands/server.js'.

Then we call child.stdout.on with 'data' to listen for stdout outputs.

In the function we pass into child.stdout.on , we log the output data with console.log and append the data to scriptOutput after it’s converted to a string.

Likewise, we call child.stderr.on to listen to stderr output by calling child.stderr.on with 'data'.

The callback is the same.

Finally, we call child.on with 'close' to get the exit code when the child process finishes running.

Conclusion

To spawn child process and get terminal output live with Node.js, we can use the child_process module’s spawn method.