test.cpp

#include <iostream>    // for using std, printf(),...
#include <unistd.h>    // for using fork()

int main(int argc, char** argv)
{
	printf("[PID:%d] Hello world\n", getpid());
	
	int a = 0;
	
	int pid = fork();
	printf("[PID:%d] Fork pid : %d\n", getpid(), pid);

	if(pid != 0)
	{
		// Parent process
		for(int i = 0; i < 3; i++)
		{
			a++;
			printf("[PID:%d] This is Parent process, forked pid = %d, a = %d\n", getpid(), pid, a);
		}
	}
	else
	{
		// Child process
		for(int i = 0; i < 5; i++)
		{
			a--;
			printf("[PID:%d] This is Child process, forked pid = %d, a = %d\n", getpid(), pid,  a);		
		}
	}
	
	printf("[PID:%d] Goodbye, a = %d\n", getpid(), a);
	
	return 0;
}