/* File:  ~liux/public_html/courses/cop4610/examples/simple-fork.cc
   Purpose: Demonstrate how to use fork system call COP4610
   Author:  Xiuwen Liu
   On the web: 
     http://www.cs.fsu.edu/~liux/courses/cop4610/examples/simple-fork.cc
   Compile:
     g++ -o simple-fork simple-fork.cc
*/
/* One running example
   ./simple-fork running.out
   */
/* more running.out
   A message line with i = 0 from 1624 whose parent is 14850
   A message line with i = 1 from 1624 whose parent is 14850
   A message line with i = 1 from 1625 whose parent is 1624
   A message line with i = 2 from 1625 whose parent is 1624
   A message line with i = 2 from 1624 whose parent is 14850
   A message line with i = 2 from 1627 whose parent is 1625
   A message line with i = 2 from 1626 whose parent is 1624
   */
/* Questions:
   1. How many new processes are created by running this program?
   2. Can you explain why the file "running.out" contains the information
      as shown above?
*/
   
#include <sys/types.h>
#include <unistd.h>
#include <iostream.h>
#include <fstream.h>
#include <string.h>

int main(int argc, char *argv[])
{
  char fname[256];
  if (argc <2) {
    cout << "Please give a file name to save output messages: ";
    cin >> fname;
  }
  else {
    strcpy(fname,argv[1]);
  }
  ofstream outFile(fname);
  int i = 0;
  while( i < 3) {
    cout << "A message line with i = " << i << endl;
    outFile << "A message line with i = " << i 
	   << " from " << getpid() << " whose parent is "
	   << getppid() << endl;
    fork();
    i++;
  }
  outFile.close();
  return 0;
}