cppreference.com > Standard C Date & Time > clock clock Syntax:
      #include <time.h>
      clock_t clock( void );
The clock() function returns the processor time since the program started, or -1 if that information is unavailable. To convert the return value to seconds, divide it by CLOCKS_PER_SEC. (Note: if your compiler is POSIX compliant, then CLOCKS_PER_SEC is always defined as 1000000.) Related topics: asctime ctime time