gistfile1.c

// gcc -o test test.c
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
    int i;
    time_t t;
    struct tm *tmp;
    char datestr[256];

    for (;;) {
        t = time(NULL);
        tmp = localtime(&t);

        strftime(datestr, sizeof(datestr), "%Y/%m/%d %H:%M:%S", tmp);
        printf("date: %s\n", datestr);
        sleep(1);
    }
    return 0;
}