In C, How to get full timestamp (even after seconds) in linux?

Question

I get a stream of bytes, after each 2000 bytes, I want to create a new file and store it. as it is a continuous stream of bytes, I cant use counter etc. So, I want to use system time stamp to identify file uniquely like filename.

I found some threads to get system time stamp, but there I am seeing till seconds. Is there any other way, with which we can get full timestamp in C, linux OS (timestmap like: 2011-11-08 18:02:08.954092000)? In all thread, I am seeing only till seconds like 2011-11-08 18:02:08

Answer 1

Linux has clock_gettime() with nanosecond resolution.

Example code

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

int main(void) {
    unsigned mult = 0;
    struct timespec t0, t1;
    clock_gettime(CLOCK_REALTIME, &t0);
    for (unsigned k = 0; k < 10000000; k++) mult *= k; // no overflow!
    clock_gettime(CLOCK_REALTIME, &t1);

    printf("%lld.%09ld --> %lld.%09ld\n",
          (long long)t0.tv_sec, t0.tv_nsec,
          (long long)t1.tv_sec, t1.tv_nsec);
    return 0;
}

On my machine (FreeBSD/Unix but should be the same as any Linux), the code above prints

1438167485.022409606 --> 1438167485.055779608