Suspends the calling thread for the specified number of microseconds.
#include <unistd.h>
int usleep (
useconds_t useconds);
(IN) Specifies the microseconds to suspend the calling thread. The value must be less than 1,000,000.
When the requested time has elapsed, returns 0. If it returns before the sleep interval has elapse, returns -1 and sets errno to indicate the error.
Currently usleep is implemented on a mechanism that has precision of only a few milliseconds, so the time at which the calling thread returns cannot be more accurate than about 10 milliseconds.