C++ obtaining milliseconds time on Linux -- clock() doesn't seem to work properly

hasen picture hasen · Feb 25, 2009 · Viewed 262.9k times · Source

On Windows, clock() returns the time in milliseconds, but on this Linux box I'm working on, it rounds it to the nearest 1000 so the precision is only to the "second" level and not to the milliseconds level.

I found a solution with Qt using the QTime class, instantiating an object and calling start() on it then calling elapsed() to get the number of milliseconds elapsed.

I got kind of lucky because I'm working with Qt to begin with, but I'd like a solution that doesn't rely on third party libraries,

Is there no standard way to do this?

UPDATE

Please don't recommend Boost ..

If Boost and Qt can do it, surely it's not magic, there must be something standard that they're using!

Answer

CTT picture CTT · Feb 26, 2009
#include <sys/time.h>
#include <stdio.h>
#include <unistd.h>
int main()
{
    struct timeval start, end;

    long mtime, seconds, useconds;    

    gettimeofday(&start, NULL);
    usleep(2000);
    gettimeofday(&end, NULL);

    seconds  = end.tv_sec  - start.tv_sec;
    useconds = end.tv_usec - start.tv_usec;

    mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5;

    printf("Elapsed time: %ld milliseconds\n", mtime);

    return 0;
}