pcntl_signal_get_handler

<?php         $windowsHandler = null;

        if ($handleInterruptsUnix) {

            pcntl_async_signals(true);

            $prevHandler = pcntl_signal_get_handler(SIGINT);

            pcntl_signal(SIGINT, function ($sig) use ($runCleanup, $prevHandler, $io) {

                $io->writeError('Received SIGINT, aborting', true, IOInterface::DEBUG);

                $runCleanup();