我分叉了多个流程，我想衡量完成整个任务需要多长时间，即所有分叉的流程都完成了。请告知如何使父进程等待所有子进程终止？我想确保在正确的时间停止计时器。

这是我使用的代码：

#include <iostream>
#include <string>
#include <fstream>
#include <sys/time.h>
#include <sys/wait.h>

using namespace std;

struct timeval first,  second,  lapsed;
struct timezone tzp;

int main(int argc, char* argv[])// query, file, num. of processes.
{

    int pCount = 5; // process count

    gettimeofday (&first, &tzp); //start time

    pid_t* pID = new pid_t[pCount];

    for(int indexOfProcess=0; indexOfProcess<pCount; indexOfProcess++)
    {
        pID[indexOfProcess]= fork();

        if (pID[indexOfProcess] == 0)                // child
        {
            // code only executed by child process

            // magic here

            // The End
            exit(0);
        }
        else if (pID[indexOfProcess] < 0)    // failed to fork
        {
            cerr << "Failed to fork" << endl;
            exit(1);
        }
        else                         // parent
        {
            // if(indexOfProcess==pCount-1) and a loop with waitpid??

            gettimeofday (&second, &tzp); //stop time
            if (first.tv_usec > second.tv_usec)
            {
                second.tv_usec += 1000000;
                second.tv_sec--;
            }

            lapsed.tv_usec = second.tv_usec - first.tv_usec;
            lapsed.tv_sec = second.tv_sec - first.tv_sec;

            cout << "Job performed in " <<lapsed.tv_sec << " sec and " << lapsed.tv_usec    << " usec"<< endl << endl;

        }

    }//for

}//main