time_t start, end;time(&end); total_time = (long) difftime(end, start)

《time.h:
typedef long time_t;        /* time value */
》
time_t start, end; /* variables to hold read timing */
long total_time = 0L; /* variable to hold delta t */
time(&start);
time(&end);
total_time = (long) difftime(end, start)