communication between parent and child through pipe

Question

I want a program where the parent and child talk each other. so the output would be:

• p: value
• c: value
• p: word
• c: word

and so on.....

Below there is an example of code where the output makes first talk the parent and after the childs. How can I correct the code?

    for(int i=0; i<N; i++){
            pid=fork();
            if(pid==-1){
                    perror("fork\n");
                    exit(EXIT_FAILURE);
            }
            else if(pid==0){
                    srand(time(NULL));
                    int c;
                    read(fd[i][0], &c, 1);
                    printf("c: value: %d\n", c);
                    char word[c];
                    read(fd[i][0],&word, sizeof(word));
                    printf("c: word: %s\n", word);
                    int sum;
                    sum=c*i;
                    write(fd[i][1], &sum, sizeof(int));
                    printf("c: sended %d\n", sum);
                    int flag=0;
                    printf("flag :%d\n", flag);
                    read(fd[i][0], &flag, sizeof(int));
                    printf("c: flag= %d ->exit\n", flag);
                    exit(1);
            }else{
                    int c;
                    c=rand()%100+1;
                    write(fd[i][1], &c, sizeof(int));
                    printf("p: value: %d\n", c);
                    char word[c];
                    write(fd[i][1], &word, sizeof(word));
                    printf("p: word: %s\n", word);
                    int sum;
                    read(fd[i][0], &sum, sizeof(int));
                    printf("p: sum is: %d\n", sum);
                    int flag=1;
                    write(fd[i][1], &flag, sizeof(int));
                    printf("par: flag exit %d\n", flag);
                    wait(NULL);
            }
    }

Answer 1

To have duplex communication between two processes, you need two<\/em> pipes:

1. <\/li>
2. <\/li><\/ol>

   If you use the same pipe for both, then you can end up with a situation like the child writing something to the pipe, and directly read it back again (and the parent will never see the data).