The Linux Programming Interface

490 Chapter 23

Listing 23-3: Using nanosleep()

––––––––––––––––––––––––––––––––––––––––––––––––––––––timers/t_nanosleep.c

#define _POSIX_C_SOURCE 199309

#include <sys/time.h>

#include <time.h>

#include <signal.h>

#include "tlpi_hdr.h"

static void

sigintHandler(int sig)

{

return; /* Just interrupt nanosleep() */

}

int

main(int argc, char *argv[])

{

struct timeval start, finish;

struct timespec request, remain;

struct sigaction sa;

int s;

if (argc != 3 || strcmp(argv[1], "--help") == 0)

usageErr("%s secs nanosecs\n", argv[0]);

request.tv_sec = getLong(argv[1], 0, "secs");

request.tv_nsec = getLong(argv[2], 0, "nanosecs");

/* Allow SIGINT handler to interrupt nanosleep() */

sigemptyset(&sa.sa_mask);

sa.sa_flags = 0;

sa.sa_handler = sigintHandler;

if (sigaction(SIGINT, &sa, NULL) == -1)

errExit("sigaction");

if (gettimeofday(&start, NULL) == -1)

errExit("gettimeofday");

for (;;) {

s = nanosleep(&request, &remain);

if (s == -1 && errno != EINTR)

errExit("nanosleep");

if (gettimeofday(&finish, NULL) == -1)

errExit("gettimeofday");

printf("Slept for: %9.6f secs\n", finish.tv_sec - start.tv_sec +

(finish.tv_usec - start.tv_usec) / 1000000.0);

if (s == 0)

break; /* nanosleep() completed */

printf("Remaining: %2ld.%09ld\n", (long) remain.tv_sec,

remain.tv_nsec);