calc code execeute time on c++

double get_time(){
	struct timeval t;
	gettimeofday(&t, NULL);
	double d = t.tv_sec + (double) t.tv_usec/1000000;
	return d;
}
...
double time_start = get_time();
...
double time_end = get_time();
printf("This program has run for: %f seconds.\n",  time_end - time_start);


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

void do_something()
{
	for(int i=0;i<100000;i++)
		for(int j=0;j<10000;j++)
			;
}

int main(int arg,char ** argv)
{
	clock_t start=clock();
	do_something();
	clock_t end=clock();
	float time=(float)(end-start)/CLOCKS_PER_SEC;
	printf("%f\n",time);
	return 0;
}