无法通过stdin重定向向执行函数发送Integer。 C语言

Question

这是一项学术活动。我应该从父进程读取一个整数，将它发送给子进程，并且该子进程应该调用factorial的exec函数（必须从stdin读取并在stdout上写入）。父亲必须显示exec函数的结果。

显然，exec函数只读取了我做过的stdin重定向的垃圾（随机大值）。无法弄清楚原因。

这是主程序和exec函数（factorial）的代码：

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

#define MAX_BUFFER 80

int main (){

    int pipeFatherChild[2], pipeChildFather[2],i;
    pid_t pid;

    if(pipe(pipeFatherChild)==-1 || pipe(pipeChildFather)==-1){
        perror("pipe Error!");
        return -1;
    }

    pid = fork();

    if(pid<0){
        perror("fork Error!");
        return -1;
    }



    if(pid>0){//father
        int value;
        char result[MAX_BUFFER];

        close(pipeFatherChild[0]);
        close(pipeChildFather[1]);

        printf("Please insert nunber to calculate factorial:\n");
        scanf("%d",&value);

        write(pipeFatherChild[1],&value,sizeof(int));
        close(pipeFatherChild[1]);

        wait(NULL);//wait for child

        int ret;
        while((ret=read(pipeChildFather[0],&result,MAX_BUFFER)!=0)){
            printf("PAI DIZ: %s\n", result);
        }

        close(pipeChildFather[0]);


    }else{//child

        close(pipeFatherChild[1]);

        dup2(pipeFatherChild[0],0);
        close(pipeFatherChild[0]);

        close(pipeChildFather[0]);

        dup2(pipeChildFather[1],1);
        close(pipeChildFather[1]);

        execl("./factorial", "factorial");

        perror("Child Error\n");


    }


    return 0;
}

因子计划：

#include <stdio.h>


int factorial(int n){
    if(n==0)
        return 1;
    return n * factorial(n-1);
}


int main(){

    int n;

    fscanf(stdin,"%d", &n);
    fprintf(stdout,"Factorial of %d is %d\n", n, factorial(n));
    return 0;
}