Thread: <time.h> in program

I am trying to find out how much time it takes to complete an execution of a program in Linux, by executing it from a new process. I am using the <time.h> time() function, but I get strange numbers pushed into the clockTimeA vector, but can't figure out why. Any suggestions as to what the problem may be? Thanks.

Here is my code:

Code:

#include <ctime>
#include <iostream>
#include <fstream>
#include <vector>
#include <cmath>
#include <sys/types.h>
#include <unistd.h>

using namespace std;

int main()
{
 pid_t pid;

 time_t start, finish; //time variables

 vector <double> clockTimeA;
 double sdA;
 double meanA = 0;
 double varianceA = 0;

 ofstream OUTPUTFILE;
 OUTPUTFILE.open("Runtime_Data_Fork_Linux_A.txt");

 pid = fork();

for(int i = 0; i <= 1; i++)
{

if(pid == 0)

{ 
 start = time(NULL);

 //Process A

  ///////////////////////////////////////////////  

  execlp("/A", "A", NULL);
}// end if loop

if (pid > 0)
 {
  wait();
  cout <<"waiting for child process to finish" << "\n"; 
  //get finish time for process A

  finish = time(NULL);

 cout << "A started at: " << " " << start << " " << "and finished at: " << finish << " " << "\n";

 clockTimeA.push_back((double) (finish-start) ) ;
 cout << "1st time is: " << clockTimeA[0] << "\n" ;
 }

} // end 30 times loop
  

if(pid > 0)
{
  for(int i = 0; i < clockTimeA.size(); i++)
  {
   OUTPUTFILE << ((double) (finish-start)) << "\n";
   meanA += clockTimeA[i]/2; 
  }

  OUTPUTFILE << "\n" << "Mean" << "\n" << meanA << "\n" << "\n";

 
  for(int i = 0; i < clockTimeA.size(); i++)
  {
   varianceA += (pow((clockTimeA[i] - meanA), 2))/2 ;
  }

  sdA = sqrt(varianceA);
  OUTPUTFILE << "StdDev" << "\n" << sdA <<  endl;

}
 return 0;

}