Programming

#include<iostream>
#include<time.h>
using namespace std;
int main()
{
    system("date");
    clock_t start = clock();
         int i=9*8;
         while(i--)
         {
             int j=9999999;
             while(j--);
         }
    clock_t end = clock();
    double elapsed = ((double) (end - start)) / CLOCKS_PER_SEC;
    cout<<"elapsed:"<<elapsed<<"\n";
    system("date");
}

$./a.out
Tue Jul 27 05:14:24 PDT 2010
elapsed:17.9997
Tue Jul 27 05:14:29 PDT 2010

> ./a.out
Tue Jul 27 07:34:36 MDT 2010
6.980000
Tue Jul 27 07:34:43 MDT 2010

# ./a.out
Tue Jul 27 07:43:59 MDT 2010
3.700000
Tue Jul 27 07:44:03 MDT 2010
#

       On several other implementations, the value returned  by  clock()  also
       includes  the times of any children whose status has been collected via
       wait(2) (or another wait-type call).  Linux does not include the  times
       of  waited-for children in the value returned by clock().  The times(2)
       function, which explicitly returns  (separate)  information  about  the
       caller and its children, may be preferable.

time ./a.out

 
$cat ts.C
#include<iostream>
#include<time.h>
using namespace std;
int main()
{
clock_t start = clock();
int i=9*8;
while(i--)
{
int j=9999999;
while(j--);
}
clock_t end = clock();
cout<<"elapsed:"<<((end - start) / CLOCKS_PER_SEC)<<"\n";
}
$g++ ts.C
$time ./a.out
elapsed:17
real 0m4.364s
user 0m4.320s
sys 0m0.011s
$