SLEEP(3) Linux Programmer's Manual SLEEP(3)
sleep - sleepfor a specified number of seconds
unsigned int sleep(unsigned int seconds);
sleep() causes the calling thread to sleep either until the number of real-time seconds speci‐
fied in seconds have elapsed or until a signal arrives which is not ignored.
Zero if the requested time has elapsed, or the number of seconds left to sleep, if
the call was interrupted by a signal handler.