CODEWITHSUNDEEP
node.js
Deer Hunter
Deer Hunter

Reputation: 1221

How to detach a spawned child process in a Node.js script?

Intent: call an external application with specified arguments, and exit script.

The following script does not work as it should:

 #!/usr/bin/node
 var cp = require('child_process');
 var MANFILE='ALengthyNodeManual.pdf';
 cp.spawn('gnome-open', ['\''+MANFILE+'\''], {detached: true});

Things tried: exec - does not detach. Many thanks in advance

Upvotes: 27

Views: 34891

Answers (2)

CarbonDonuts
CarbonDonuts

Reputation: 65

My solution to this problem:

app.js

require('./spawn.js')('node worker.js');

spawn.js

module.exports = function( command ) {
    require('child_process').fork('./spawner.js', [command]); 
};

spawner.js

require('child_process').exec(
    'start cmd.exe @cmd /k "' + process.argv[2] + '"', 
    function(){}
);
process.abort(0);

Upvotes: 2

Vadim Baryshev
Vadim Baryshev

Reputation: 26189

From node.js documentation:

By default, the parent will wait for the detached child to exit. To prevent the parent from waiting for a given child, use the child.unref() method, and the parent's event loop will not include the child in its reference count.

When using the detached option to start a long-running process, the process will not stay running in the background unless it is provided with a stdio configuration that is not connected to the parent. If the parent's stdio is inherited, the child will remain attached to the controlling terminal.

You need to modify your code something like this:

#!/usr/bin/node
var fs = require('fs');
var out = fs.openSync('./out.log', 'a');
var err = fs.openSync('./out.log', 'a');

var cp = require('child_process');
var MANFILE='ALengthyNodeManual.pdf';
var child = cp.spawn('gnome-open', [MANFILE], { detached: true, stdio: [ 'ignore', out, err ] });
child.unref();

Upvotes: 55

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