// crt_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 );

int main( void )
{
   long    i = 6000000L;
   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() )
      ;
}

#define TIMEOUT_IN_SECONDS  100 
time_t t;
int i;

i =  0 ;
t = time( 0 );
while( (time( 0 ) - t) < TIMEOUT_IN_SECONDS ) {
  i++;
  // еще какая-нибудь глупость
}
printf ("Цикл сделал %d итераций за %d секунд\n", i, TIMEOUT_IN_SECONDS);