MSDN clock

经常忘记写一下：

Example

/* CLOCK.C: This example prompts for how long
* the program is to run and then continuously
* displays the elapsed time for that period.
*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void sleep( clock_t wait );
void main( void )
{
  long    i = 600000L;
  clock_t start, finish;
  double  duration;
  /* Delay for a specified time. */
  printf( "Delay for three seconds\n" );
  sleep( (clock_t)3 * CLOCKS_PER_SEC );
  printf( "Done!\n" );
  /* Measure the duration of an event. */
  printf( "Time to do %ld empty loops is ", i );
  start = clock();
  while( i-- )
     ;
  finish = clock();
  duration = (double)(finish - start) / CLOCKS_PER_SEC;
  printf( "%2.1f seconds\n", duration );
}
/* Pauses for a specified number of milliseconds. */
void sleep( clock_t wait )
{
  clock_t goal;
  goal = wait + clock();
  while( goal > clock() )
     ;
}

Output

Delay for three seconds
Done!
Time to do 600000 empty loops is 0.1 seconds