Child process not getting killed with Node.JS

Question

I used child_process.exec / child_process.spawn to fork a new process and then kill it using child.kill / process.kill. It works fine with simple binary executables, such as cat / ls, and the child process just get killed.

However, when get to the scripts (say P1) that forks another child process (say P2), only the script interpreter P1 get killed, not the child process P2.

QUESTION: is there any way that getting such child process P2 killed with Node.JS?

Code works fine with run_and_kill('ls -Al /usr/lib'), but not OK with run_and_kill('firefox'):

function run_and_kill(cmd) {
    var exec = require('child_process').exec,
        ls = exec(cmd);
    console.log('Child process started: %d', ls.pid);
    ls.on('exit', function(code, signal) {
        console.log('exit with code %s and signal %s', code, signal);
    });
    ls.kill();
}

you can try to kill them manually (probably P2 ignores SIGHUP) - http://stackoverflow.com/questions/392022/best-way-to-kill-all-child-processes — Andrey Sidorov, Jul 26 '11 at 03:30
you know it - `ls.pid` ( https://github.com/joyent/node/blob/master/lib/child_process.js#L250 ) — Andrey Sidorov, Jul 27 '11 at 00:22
@AndreySidorov I mean PID of P2 since kill P1 does not make P2 exits. — Ghostoy, Jul 27 '11 at 01:51
you can try to pass group id when spawn p2 and use it to kill — Andrey Sidorov, Jul 27 '11 at 23:39
@AndreySidorov P1 is a read-only script not necessarily written with Node.JS. And how to get the group PID and kill P1/P2 both with Node.JS? — Ghostoy, Jul 29 '11 at 07:31
It depends on what P2 is. I'm not as familiar with Firefox, but with Chrome, as soon as you start it, the PID changes due to it's process per tab model and you are unable to kill it using the original reference to the process. This may be what is happening here. — Timothy Strimple, Apr 04 '12 at 17:10

score 4 · Answer 1 · answered Nov 24 '15 at 12:34

The safest way I've found to achieve this is creating a spawn process to kill the signal, using the child.pid as argument. Example with fork :

var process;
process = require('child_process');

var fork, child;
fork = process.fork;
child = fork('./index');

var spawn;
spawn = process.spawn;
spawn('kill', [child.pid]);
console.log('sending SIGTERM to child process (socket server)');

I typically use this in specs, mostly in beforeAll/afterAll blocks to start/kill servers (in the example './index.js').

this works, as long as *those* child processes exit too :) which they should — Alexander Mills, Oct 20 '16 at 18:31

score 2 · Answer 2 · answered Jul 20 '18 at 11:22

2

In my case the problem was the shell being used for the process. By default it's /bin/sh, and when this was being used it wasn't handling the kill signals.

To fix this you can use /bin/bash instead:

exec('your command', {
    shell: '/bin/bash',
});

answered Jul 20 '18 at 11:22

Daniel

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Any idea what the equivalent solution would be on a Windows system? – Sheldonfrith Jan 22 '23 at 03:08

score 1 · Answer 3 · answered Apr 11 '12 at 01:47

I think your P2 is neither a fork or a child of P1 but rather a parallel process spawned by it. In the case of Firefox ( at least in Linux ) the firefox app is launched by a wrapper shell script. If it's always going to be firefox, better run the binary straight from it's install folder

Child process not getting killed with Node.JS

3 Answers3