#include <unistd.h>
#include <fcntl.h>
#include <sys/wait.h>

int
main(int argc, char *argv[])
{
    pid_t pid;
    int fd, status;
    int fds[2];
    if (pipe(fds) == -1) {
        return 1;
    }

    pid = fork();
    if (pid == -1) {
        return 1;
    } else if (!pid) {
        pid = fork();
        if (pid == -1) {
            return 1;
        } else if (!pid) {
            if (close(fds[0]) == -1) {
                _exit(1);
            }
            fd = open(argv[4], O_RDONLY);
            if (fd == -1) {
                _exit(1);
            }
            if (dup2(fd, 0) == -1) {
                _exit(1);
            }
            if (dup2(fds[1], 1) == -1) {
                _exit(1);
            }
            if (close(fds[1]) == -1) {
                _exit(1);
            }
            if (close(fd) == -1) {
                _exit(1);
            }
            execlp(argv[1], argv[1], NULL);
            _exit(1);
        }
        if (wait(&status) == -1) {
            return 1;
        }

        if (WIFEXITED(status) && !WEXITSTATUS(status)) {
            if (close(fds[0]) == -1) {
                _exit(1);
            }
            if (dup2(fds[1], 1) == -1) {
                _exit(1);
            }
            if (close(fds[1]) == -1) {
                _exit(1);
            }
            execlp(argv[2], argv[2], NULL);
            _exit(1);

            if (wait(NULL) == -1) {
                return 1;
            }
        }
    }
    wait(NULL);

    pid = fork();
    if (pid == -1) {
        return 1;
    } else if (!pid) {
        fd = open(argv[5], O_CREAT | O_WRONLY | O_APPEND, 0777);
        if (fd == -1) {
            _exit(1);
        }
        if (dup2(fds[0], 0) == -1) {
            _exit(1);
        }
        if (dup2(fds[1], 1) == -1) {
            _exit(1);
        }
        if (close(fds[0]) == -1) {
            return 1;
        }
        if (close(fds[1]) == -1) {
            return 1;
        }
        execlp(argv[3], argv[3], NULL);
        _exit(1);
    }

    if (close(fds[0]) == -1) {
        return 1;
    }
    if (close(fds[1]) == -1) {
        return 1;
    }
    if (wait(NULL) == -1) {
        return 1;
    }
    return 0;
}