Calculate the execution time of microseconds

cost_us.c

/* use gettimeofday() to calculate the execution time in microseconds */
#include <sys/time.h>
long timecost(void (*dosomething)())
{
	struct timeval start, end;
	long cost;

	gettimeofday(&start, NULL);
	dosomething();
	gettimeofday(&end, NULL);
	cost = end.tv_usec - start.tv_usec;
	printf("cost time: %ld us", cost);

	return cost;
}