Thread: Calculate time in microseconds or nanoseconds

Hello

In Java the following loop calculates me the results in nanoseconds and with the addition of /1000 therefore in microseconds.
Here the incomplete programm. The important part is the loop of 39 and two values which will be printed out.

Code:

for(int sx=1; sx<=39; sx++){
             long startTime = java.lang.System.nanoTime();       
             System.out.println("Hello world");
             long endTime = java.lang.System.nanoTime();
             System.out.println((endTime - startTime)/1000); 
         }

I would like to do the same in C:
There are some examples in the internet unfortunately it returns 0 microseconds.

This is the code I have found in the internet:

Code:

/**
 * Get time difference in microseconds
 * */
  
#include <stdio.h>
#include <sys/time.h>
  
double time_diff(struct timeval x , struct timeval y);
  
int main()
{  
    int i;
     
    struct timeval before , after;
    gettimeofday(&before , NULL);
   
    //Time taking task
    for (i=1 ; i <= 100 ; i++)
    {
        printf("%d %d %d n",i, i*i, i*i*i);
    }
   
    gettimeofday(&after , NULL);
 
    printf("Total time elapsed : %.0lf us" , time_diff(before , after) ); 
   
    return 0;
}
 
double time_diff(struct timeval x , struct timeval y)
{
    double x_ms , y_ms , diff;
     
    x_ms = (double)x.tv_sec*1000000 + (double)x.tv_usec;
    y_ms = (double)y.tv_sec*1000000 + (double)y.tv_usec;
     
    diff = (double)y_ms - (double)x_ms;
     
    return diff;
}

I have changed this code to:

Code:

/**
 * Get time difference in microseconds
 * */

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

double time_diff(struct timeval x , struct timeval y);

int main()
{
    int i;

    struct timeval before , after;


    //Time taking task
    for (i=1 ; i <= 39 ; i++)
    {
        gettimeofday(&before , NULL);
        printf("Hello world\n");
        gettimeofday(&after , NULL);
        printf("Total time elapsed : %.0lf us\n" , time_diff(before , after) );
    }

    return 0;
}

double time_diff(struct timeval x , struct timeval y)
{
    double x_ms , y_ms , diff;

    x_ms = (double)x.tv_sec + (double)x.tv_usec;
    y_ms = (double)y.tv_sec + (double)y.tv_usec;

    diff = (double)y_ms - (double)x_ms;

    return diff;
}

This is another example:
Again 0 value.

Code:

#include <sys/time.h>
#include <stdio.h>
#include <unistd.h>
int main()
{
    struct timeval start, end;

    long mtime, seconds, useconds;


    for(int sx=1; sx<=39; sx++){

        gettimeofday(&start, NULL);
        printf("Hello world");
        gettimeofday(&end, NULL);

        printf("Elapsed time: %ld microsecons\n", end.tv_usec - start.tv_usec);

     }

    return 0;
}

Any idea?

Thx,
Troix