¹³ In the process, system() blocks SIGCHLD, which will cause a SIGCHLD signal to be delivered to the program immediately before system() returns (but after system() has called wait() on the process it spawned), so programs that use signal handlers need to be careful to handle this possibly spurious signal. The system() function also ignores SIGINT and SIGQUIT, which means that a tight loop calling system() repeatedly could be uninterruptible by everything except SIGSTOP and SIGKILL.