#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
int capacity;
static void sig_alarm_popen(int signo){
   	printf ("Popen capacity= %d\n", capacity);
    exit (0);
}
static void sig_alarm_pipe(int signo){
   	printf ("Pipe capacity= %d\n", capacity);
    exit (0);
}

int main(void)  {
    pid_t pid;
    FILE *pf;
    int pfd[2];
    int i, status;
 
    pid=fork();
    if (pid==0) { /*child*/
        FILE *pf;
        signal(SIGALRM, sig_alarm_popen);
        if ((pf = popen("./p2.child", "w")) == NULL) {
            perror("popen");
            exit(1);
        }
        capacity=0;
        alarm(1);
        while (fprintf(pf, "a")>0) {
            capacity++;
            alarm(1);
        }
    } else  {
        sleep(1);
        signal(SIGALRM, sig_alarm_pipe);
        if (pipe(pfd) < 0) {
            perror("pipe");
            exit(1);
        }
        if (fork()==0) {
            dup2(pfd[0], 0);
            close(pfd[1]);
            execl("./p2.child", "p2.child", (char *) 0);
            perror("exec");
            exit(127);
        }
        capacity=0;
        alarm(1);
        close(pfd[0]);
        while (write(pfd[1], "a", 1)>0) {
            capacity++;
            alarm(1);
        }
    }
}