File size: 1,867 Bytes
4559903 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 | #define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <time.h>
#include <err.h>
#include <sys/timerfd.h>
static void
print_elapsed_time(void)
{
static struct timespec start;
struct timespec curr;
static int first_call = 1;
int secs, nsecs;
if (first_call) {
first_call = 0;
if (clock_gettime(CLOCK_MONOTONIC, &start) == -1)
err(1, "clock_gettime");
}
if (clock_gettime(CLOCK_MONOTONIC, &curr) == -1)
err(1, "clock_gettime");
secs = curr.tv_sec - start.tv_sec;
nsecs = curr.tv_nsec - start.tv_nsec;
if (nsecs < 0) {
secs--;
nsecs += 1000000000;
}
printf("%d.%03d: ", secs, (nsecs + 500000) / 1000000);
}
int
main(int argc, char *argv[])
{
struct itimerspec new_value;
int max_exp, fd;
struct timespec now;
uint64_t exp, tot_exp;
ssize_t s;
if ((argc != 2) && (argc != 4)) {
fprintf(stderr, "%s init-secs [interval-secs max-exp]\n", argv[0]);
return 1;
}
if (clock_gettime(CLOCK_MONOTONIC, &now) == -1)
err(1, "clock_gettime");
new_value.it_value.tv_sec = now.tv_sec + atoi(argv[1]);
new_value.it_value.tv_nsec = now.tv_nsec;
if (argc == 2) {
new_value.it_interval.tv_sec = 0;
max_exp = 1;
} else {
new_value.it_interval.tv_sec = atoi(argv[2]);
max_exp = atoi(argv[3]);
}
new_value.it_interval.tv_nsec = 0;
fd = timerfd_create(CLOCK_MONOTONIC, 0);
if (fd == -1)
err(1, "timerfd_create");
if (timerfd_settime(fd, TFD_TIMER_ABSTIME, &new_value, NULL) == -1)
err(1, "timerfd_settime");
print_elapsed_time();
printf("timer started\n");
for (tot_exp = 0; tot_exp < (uint64_t)max_exp;) {
s = read(fd, &exp, sizeof(uint64_t));
if (s != sizeof(uint64_t))
err(1, "read");
tot_exp += exp;
print_elapsed_time();
printf("read: %llu; total=%llu\n",
(unsigned long long)exp,
(unsigned long long)tot_exp);
}
return 0;
}
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