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();
}

Answer 1

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').

Answer 2

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

Answer 3

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',
});