Thread: Parent and Child Processes

I'm trying to understand how child and parent processes work....this is my output.

Child0Parent0
ChildParent10

Child2
Parent0

Child3
Parent0

Child4
Parent0

Can anyone tell me why Parent isn't incrementing? My code is below:

Code:

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>


char mynum='0';
int main(void)
{
    int i;
    pid_t fork_return;
    static char buffer[10];
    fork_return = fork();
    if (fork_return == 0)
    {
        strcpy(buffer, "CHILD"); 
        for (i=0; i<5; ++i) 
        {
            mynum=i + '0';
            sleep(1); 
            write(1, buffer, sizeof(buffer));
            write(1, &mynum, 1);
            write(1, "\n", 1);
        }
        return 0;
    }
    else
    {
        strcpy(buffer, "PARENT"); 
        for (i=0; i<5; ++i) 
        {
            sleep(1); /*5 times each*/
            write(1, buffer, sizeof(buffer));
            write(1, &mynum, 1);
            write(1, "\n", 1);
        }
        return 0;
    }
}

Because after the fork(), both processes have unique copies of all variables.

Incrementing a variable in the child has no effect in the parent.

You need proper shared memory for this to happen.