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utilityProcess creates a child process with
Node.js and Message ports enabled. It provides the equivalent of child_process.fork API from Node.js
but instead uses Services API from Chromium to launch the child process.
Process: Main
Methods?
utilityProcess.fork(modulePath[, args][, options])?
modulePathstring - Path to the script that should run as entrypoint in the child process.argsstring[] (optional) - List of string arguments that will be available asprocess.argvin the child process.
Returns UtilityProcess
utilityProcess.fork can only be called after the ready event has been emitted on App.
Class: UtilityProcess?
Instances of the
UtilityProcessrepresent the Chromium spawned child process with Node.js integration.
UtilityProcess is an EventEmitter.
Instance Methods?
child.postMessage(message, [transfer])?
messageanytransferMessagePortMain[] (optional)
Send a message to the child process, optionally transferring ownership of
zero or more MessagePortMain objects.
For example:
// Main process
const { port1, port2 } = new MessageChannelMain()
const child = utilityProcess.fork(path.join(__dirname, 'test.js'))
child.postMessage({ message: 'hello' }, [port1])
// Child process
process.parentPort.once('message', (e) => {
const [port] = e.ports
// ...
})
child.kill()?
Returns boolean
Terminates the process gracefully. On POSIX, it uses SIGTERM but will ensure the process is reaped on exit. This function returns true if the kill is successful, and false otherwise.
Instance Properties?
child.pid?
A Integer | undefined representing the process identifier (PID) of the child process.
Until the child process has spawned successfully, the value is undefined. When
the child process exits, then the value is undefined after the exit event is emitted.
const child = utilityProcess.fork(path.join(__dirname, 'test.js'))
console.log(child.pid) // undefined
child.on('spawn', () => {
console.log(child.pid) // Integer
})
child.on('exit', () => {
console.log(child.pid) // undefined
})
You can use the pid to determine if the process is currently running.
child.stdout?
A NodeJS.ReadableStream | null that represents the child process's stdout.
If the child was spawned with options.stdio[1] set to anything other than 'pipe', then this will be null.
When the child process exits, then the value is null after the exit event is emitted.
// Main process
const { port1, port2 } = new MessageChannelMain()
const child = utilityProcess.fork(path.join(__dirname, 'test.js'))
child.stdout.on('data', (data) => {
console.log(`Received chunk ${data}`)
})
child.stderr?
A NodeJS.ReadableStream | null that represents the child process's stderr.
If the child was spawned with options.stdio[2] set to anything other than 'pipe', then this will be null.
When the child process exits, then the value is null after the exit event is emitted.
Instance Events?
Event: 'spawn'?
Emitted once the child process has spawned successfully.
Event: 'error' Experimental?
Returns:
typestring - Type of error. One of the following values:FatalError
locationstring - Source location from where the error originated.reportstring -Node.js diagnostic report.
Emitted when the child process needs to terminate due to non continuable error from V8.
No matter if you listen to the error event, the exit event will be emitted after the
child process terminates.
Event: 'exit'?
Returns:
codenumber - Contains the exit code for the process obtained from waitpid on POSIX, or GetExitCodeProcess on Windows.
Emitted after the child process ends.
Event: 'message'?
Returns:
messageany
Emitted when the child process sends a message using process.parentPort.postMessage().