calls2.c

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

#define NUM 10000000

void
child(int wfd, int rfd)
{
        int i;
        for (i = 1; i <= NUM; i++) {
                int n;

                n = write(wfd, &i, sizeof i);
                if (n != sizeof i) {
                        fprintf(stderr, "write\n");
                }

                n = read(rfd, &i, sizeof i);
                if (n != sizeof i) {
                        fprintf(stderr, "read\n");
                }
        }
}

void
parent(int wfd, int rfd)
{
        for (;;) {
                int i, n;

                n = read(rfd, &i, sizeof i);
                if (n != sizeof i) {
                        fprintf(stderr, "read\n");
                }

                n = write(wfd, &i, sizeof i);
                if (n != sizeof i) {
                        fprintf(stderr, "write\n");
                }

                if ((i % (NUM / 1000)) == 0) {
                        fprintf(stderr, "%d\n", i);
                }
                if (i == NUM) {
                        fprintf(stderr, "done\n");
                        break;
                }
        }
}
int
main(int ac, char *av[])
{
        int fds_a[2], fds_b[2];

        if (pipe(fds_a) < 0) {
                fprintf(stderr, "pipe\n");
                return EXIT_FAILURE;
        }
        if (pipe(fds_b) < 0) {
                fprintf(stderr, "pipe\n");
                return EXIT_FAILURE;
        }

        pid_t pid = fork();
        if (pid < 0) {
                fprintf(stderr, "pipe\n");
                return EXIT_FAILURE;
        }

        if (pid == 0) {
                close(fds_a[0]);
                close(fds_b[1]);
                child(fds_a[1], fds_b[0]);
        } else {
                close(fds_a[1]);
                close(fds_b[0]);
                parent(fds_b[1], fds_a[0]);
        }

        return EXIT_SUCCESS;
}