To summarize and fix a minor issue in a post by Johannes Weiss (non-German keyboard, sorry):
POSIX- usleep(), . , , :
#include <unistd.h>
usleep(500000);
POSIX ( man- Gentoo Linux POSIX.1-2001), nanosleep(), , . :
#include <time.h>
struct timespec t;
t.tv_sec = 0;
t.tv_nsec = 500000000;
nanosleep(&t, NULL);
nanosleep() "rem" , - . NULL . , ( ) , , , - .