Is there any way, how to run a new independent process from node.js process?
Example:
console.log('Starting new process')
// fork bash script.sh
process.exit()
Node.js process is dead and script.sh still running.
I don't know how to implement, which function should I use?
Related
So I have some code which runs a command in a spawned child process. I do this using the execa module.
const childProcess = execa.command('yarn start');
const localhostStarted = await waitForLocalhost({ port: 8000 });
expect(localhostStarted.done).toBe(true);
childProcess.kill('SIGINT', { forceKillAfterTimeout: 2000 });
The yarn start command executes webpack-dev-server in another child process of its own. However when I kill the childProcess that I spawned, it does not automatically kill its spawned webpack-dev-server process. It is known to be an issue here https://github.com/webpack/webpack-dev-server/issues/2168.
To fix this I add manual listeners for SIGINT & SIGTERM inside my script which runs when yarn start is called
['SIGINT', 'SIGTERM'].forEach((signal) => {
console.log('registering events');
process.on(signal, () => {
console.log('received signal', signal);
devServer.close(() => {
console.log('exiting proces');
process.exit(0);
});
});
});
This fixes the issue on my local machine and when I kill child process I spawn, it kills all its descendents i.e the dev-server process too.
However, this fix still does not work on CI, and since the child process gets killed on CI but not the dev-server process, my tests dont exit and keeps hanging.
My local machine is OSX 10.15 but on CI we use ubuntu. If I change CI to use macos 10.15, then the fix works on CI too.
I am unable to find any docs on this issue which explains the different behaviour on why the signal of SIGTERM is not received by the dev-server process on ubuntu machines but receives fine on mac machines.
If this is possible I want to execute some command or script when one npm script is killed with CTRL + C. For example if gulp watch is interrupted.
It is possible?
The exit event is emitted when the process is about to exit. There is no way to prevent the exiting of the event loop at this point, and once all 'exit' listeners have finished running the process will exit. Therefore you must only perform synchronous operations in this handler.
From Node.js process docs
To spawn some command synchronously, you could look into Synchronous Process Creation:
process.on('exit', code => {
require('child_process').spawnSync(...);
require('child_process').execSync(...);
require('child_process').execFileSync(...);
});
If you have a custom script that you run through npm you can listen to the exit event of the process or child process. e.g.
process.on('exit', () => {
console.log('I am exiting....');
});
More info here
I try to run external application in node.js with child process like the following
var cp = require("child_process");
cp.exec("cd "+path+" && ./run.sh",function(error,stdout,stderr){
})
However when I try to run it stuck, without entering the callback
run.sh starts a server, when I execute it with cp.exec I expect it run asynchronously, such that my application doesn't wait until server termination. In callback I want to work with server.
Please help me to solve this.
cp.exec get the working directory in parameter options
http://nodejs.org/docs/latest/api/child_process.html#child_process_child_process_exec_command_options_callback
Use
var cp = require("child_process");
cp.exec("./run.sh", {cwd: path}, function(error,stdout,stderr){
});
for running script in the "path" directory.
The quotes are interpreted by the shell, you cannot see them if you just look at ps output.
I'm running require('child_process').exec('npm install') as a child process in a node.js script, but I want it to retain console colors. I'm running in windows, but want this script to be portable (e.g. to linux). How do I start a process that think's it's being run from the console?
Note: I'd rather not have npm-specific answers, but an answer that allows me to trick any command.
You can do this by letting the child process inherit the master process' stdio streams. This means you need to user spawn rather than exec, and this what you'd do:
var spawn = require('child_process').spawn;
var child = spawn('npm', ['install'], {
stdio: 'inherit'
});
I am trying to run my Node application as a Grunt task. I need to spawn this as a child process, however, to allow me to run the watch task in parallel.
This works:
grunt.registerTask('start', function () {
grunt.util.spawn(
{ cmd: 'node'
, args: ['app.js']
})
grunt.task.run('watch:app')
})
However, when changes are detected by the watch task, this will trigger the start task again. Before I spawn another child process of my Node app, I need to kill the previous one.
I can't figure out how to kill the process, however. Something like this does not work:
var child
grunt.registerTask('start', function () {
if (child) child.kill()
child = grunt.util.spawn(
{ cmd: 'node'
, args: ['app.js']
})
grunt.task.run('watch:app')
})
It appears that:
Even though I store the spawned process in a variable outside of the function context, it does not persist, so the next time the start task is run, child is undefined.
child has no kill function…
Take a look at grunt-nodemon which handles a lot of the headaches related to spawning a child process.
This is because grunt-contrib-watch currently spawns all task runs as child processes. So the variable child is not within the same process context. Fairly soon, grunt-contrib-watch#0.3.0 will be released with a nospawn option. This will let you configure the watch to spawn task runs within the same context and would make your above example work.
Take a look at this issue for a little more information:
https://github.com/gruntjs/grunt-contrib-watch/issues/45