How to sleep for 3 seconds in C language

Example of the millisecond sleep function:

/*
Example: sleep 3 seconds in C language
*/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>

#include <errno.h>

int msleep(long msec)
{
    struct timespec ts;
    int res;

    if (msec < 0)
    {
        errno = EINVAL;
        return -1;
    }

    ts.tv_sec = msec / 1000;
    ts.tv_nsec = (msec % 1000) * 1000000;

    do {
        res = nanosleep(&ts, &ts);
    } while (res && errno == EINTR);

    return res;
}

int main(int argc, char *argv[]) {
    time_t now = time(0);
    printf("the time： %ld\n", now);

	msleep(3000); // Sleep for 3 seconds

	now = time(0);
    printf("the time： %ld\n", now);
    return 0;
}