/////////////////////////////////////////
// Fork.cpp
// This program forks children.  It prints child process ids.
// It works with global and local variables.
//////////////////////////////////////////
//  Working with UNIX processes: To compile and run:
//    g++ fork.cpp -o fork 
//    chmod u+x fork
//    ./fork
//    ./fork > fork.out
/////////////////////////////////////////
#include <sys/types.h>  // defines pid_t
#include <unistd.h>		// defines fork
#include <iostream>	// defines cout, cin
#include <stdlib.h>     // defines exit()
#include <sys/wait.h>   // defines wait()
using namespace std;

int global=0;

class Process {
public:
   Process()    {} 
   int count(char text);
private:
   int index;
};

int Process::count(char text)
{
      index=0;

      // Get process ID
      pid_t  identification = getpid();
      cout << "Started: " << identification << endl;

      // Print text 5000 times in rows of 10
      for (int i=0; i<50000; i++) {
            cout << text << index++; 
	    if (i%10==0) cout << " g" << global++ << endl;
      }

      // Print that process is done - with its ID
      cout << "Completed: " << identification << endl;
      exit(0);   // do not return
}

int main()
{
      Process child;
      int stat;        // returns a status from the child here

      // Create children
      if (fork() == 0)  // child process
         child.count('a');  
      if (fork() == 0)  // child process
         child.count('b');  
      if (fork() == 0)  // child process
         child.count('c');  
      // Have parent pause to wait for all children to complete before terminating
      //wait(&stat);
      //wait(&stat);
      //wait(&stat);
      sleep(10);    // Sleep 10 seconds if wait() does not work
      cout << "All done" << endl;
}