How to detect if a Node spawned process is still running?

Question

I can spawn a process like:

var spawn = require('child_process').spawn;

var topicListener = spawn('python', ['topic_listener.py','Node.js'], {env: {
    TWITTER_CONSUMER_SECRET: process.env.TWITTER_CONSUMER_SECRET,
    TWITTER_CONSUMER_KEY: process.env.TWITTER_CONSUMER_KEY,
    TWITTER_TOKEN_SECRET: process.env.TWITTER_TOKEN_SECRET,
    TWITTER_ACCESS_TOKEN: process.env.TWITTER_ACCESS_TOKEN
}});

topicListener.stdout.on('data', function (data) {
    console.log(data.toString());
});

topicListener.stderr.on('data', function (data) {
    console.log(data.toString());
});

topicListener.on('close', function (code) {
    console.log("EXITED " + code);
});

So of course I can control it all asycnchronously with .on(close, ...) but is there any other way to control if a process is still alive?

score 4 · Answer 1 · answered May 03 '17 at 16:53

4

topicListener.on('exit', function (code) { 
 topicListener = null;
 console.log("EXITED " + code);
});

If topiclistener is null, the process is gone

answered May 03 '17 at 16:53

Ben Bieler

1,518
1
14
22

does this work if the process crashes? – Switch386 Nov 04 '22 at 16:30

score 1 · Accepted Answer · answered Oct 28 '15 at 05:03

1

spawn('python', ['topic_listener.py','Node.js'].. Return Child process Object. Use topicListener.pid to find unique ID associated with the process if it's alive.

answered Oct 28 '15 at 05:03

n_rao

155
1
5

I already had tested that but even if process was ended pid was still a defined number – diegoaguilar Oct 28 '15 at 05:05
1

`topicListener.on('close', function (code) { topicListener = null; console.log("closed" + code); }); ` `topicListener.on('exit', function (code) { topicListener = null; console.log("EXITED " + code); });`
if `topiclistener` is `null` process is absent. – n_rao Oct 28 '15 at 05:31

How to detect if a Node spawned process is still running?

2 Answers2