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Signals are standardized messages in Unix-like operating systems.

Signal Callbacks

EventLoop::onSignal() can be used to react to signals sent to the process.


use Revolt\EventLoop;

// Let's tick off output once per second, so we can see activity.
EventLoop::repeat(1, function (): void {
    echo "tick: ", date('c'), "\n";

// What to do when a SIGINT signal is received
EventLoop::onSignal(SIGINT, function (): void {
    echo "Caught SIGINT! exiting ...\n";


As should be clear from the fundamentals, signal callbacks may be enabled, disabled and canceled like any other event callback.

Generally, if all callbacks are gone and only the signal callback still exists, you want to exit the event loop unless you’re not actively waiting for that event to happen.

Signal Number Availability

ext-uv exposes UV::SIG* constants for watchable signals. Applications using the EventDriver will need to manually specify the appropriate integer signal numbers when registering signal callbacks or rely on ext-pcntl.