[c] Best timing method in C?

If you don't want CPU time then I think what you're looking for is the timeval struct.

I use the below for calculating execution time:

int timeval_subtract(struct timeval *result,                                                                                                                                        
                     struct timeval end,                                                                                                                                                 
                     struct timeval start)                                                                                                                                               
{                                                                                                                                                                                   
        if (start.tv_usec < end.tv_usec) {                                                                                                                                          
                int nsec = (end.tv_usec - start.tv_usec) / 1000000 + 1;                                                                                                             
                end.tv_usec -= 1000000 * nsec;                                                                                                                                      
                end.tv_sec += nsec;                                                                                                                                                 
        }                                                                                                                                                                           
        if (start.tv_usec - end.tv_usec > 1000000) {                                                                                                                                
                int nsec = (end.tv_usec - start.tv_usec) / 1000000;                                                                                                                 
                end.tv_usec += 1000000 * nsec;                                                                                                                                      
                end.tv_sec -= nsec;                                                                                                                                                 
        }                                                                                                                                                                           

        result->tv_sec = end.tv_sec - start.tv_sec;                                                                                                                                 
        result->tv_usec = end.tv_usec - start.tv_usec;                                                                                                                              

        return end.tv_sec < start.tv_sec;                                                                                                                                           
}                                                                                                                                                                                   

void set_exec_time(int end)                                                                                                                                                         
{                                                                                                                                                                                   
        static struct timeval time_start;                                                                                                                                           
        struct timeval time_end;                                                                                                                                                    
        struct timeval time_diff;                                                                                                                                                   

        if (end) {                                                                                                                                                                  
                gettimeofday(&time_end, NULL);                                                                                                                                      
                if (timeval_subtract(&time_diff, time_end, time_start) == 0) {                                                                                                      
                        if (end == 1)                                                                                                                                               
                                printf("\nexec time: %1.2fs\n",                                                                                                                     
                                        time_diff.tv_sec + (time_diff.tv_usec / 1000000.0f));                                                                                       
                        else if (end == 2)                                                                                                                                          
                                printf("%1.2fs",                                                                                                                                    
                                        time_diff.tv_sec + (time_diff.tv_usec / 1000000.0f));                                                                                       
                }                                                                                                                                                                   
                return;                                                                                                                                                             
        }                                                                                                                                                                           
        gettimeofday(&time_start, NULL);                                                                                                                                            
}                                                                                                                                                                                   

void start_exec_timer()                                                                                                                                                             
{                                                                                                                                                                                   
        set_exec_time(0);                                                                                                                                                           
}                                                                                                                                                                                   

void print_exec_timer()                                                                                                                                                             
{                                                                                                                                                                                   
        set_exec_time(1);                                                                                                                                                           
}