What is the 'detached' option when spawning a child process, and when would you use it?

By default, a child process is tied to its parent's lifecycle in certain ways depending on the platform -- the { detached: true } option allows the child to continue running independently even after the parent process exits, useful for launching a genuinely independent background process (like starting a separate long-running daemon) that shouldn't be killed just because the process that launched it terminates; combined with child.unref(), the parent can also exit without waiting for the detached child.

const { spawn } = require('node:child_process');

const child = spawn('long-running-daemon', [], {
  detached: true,
  stdio: 'ignore', // don't keep parent alive waiting on child's stdio either
});
child.unref(); // parent process can now exit independently of the child