ping pong

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void child(int p[2]) {
    int value[1] = {0};
    while (*value < 9) {
        read(p[0], value, sizeof (int));
        printf(" < < < %d\n", *value);
        *value += 1;
        write(p[1], value, sizeof (int));
        sleep(1);
    }
    close(p[1]);
    close(p[0]);
    exit(EXIT_SUCCESS);
}

int main(void) {
    int pp[2];
    pipe(pp);
    if (fork() == 0) { child(pp); } // child() exits
    int value[1] = {0};
    while (*value < 9) {
        printf("%d > > > ", *value);
        fflush(stdout);
        *value += 1;
        write(pp[1], value, sizeof (int));
        sleep(1);
        read(pp[0], value, sizeof (int));
    }
    close(pp[0]);
    close(pp[1]);
    return 0;
}