Question

我正在使用exec，管道和叉子编写程序

我的主程序创建管道，叉子。父亲通过键盘询问一个号码，然后将其发送到另一个名为＆＃34; Factorial＆＃34; （儿子用exec）。 fatorial接收数字，计算fatorial并将结果发送回主程序......但结果总是-1。

主程序

    int pipeFromProgram[2], pipeToProgram[2],numero_keyboard= 0, num_factorial=-1
  // Forks and Pipes ..
  pipeFromProgram = createPipe();;
  pipeToProgram = createPipe();
  x = createSon();

 if(x == 0) {  //Father
    numero_teclado = escolherNumero();
    close(pipeToProgram[0]);
    write(pipeToProgram[1],&numero_teclado, BUFFER);   //The other program receives correctly the number.
    close(pipeToProgram[1]);


            close(pipeFromProgram[1]);      
    read(pipeFromProgram[0], &num_factorial,BUFFER);   //Receive the result
    printf("PIPE %d\n",num_factorial);   //The result its always -1 (declared as)
    close(pipeFromProgram[0]);  

    wait(NULL);
  }else{ 
        close(pipeToProgram[1]);        
    dup2(pipeToProgram[0], 0); 
    dup2(pipeFromProgram[1],1);
    close(pipeToProgram[0]);                
    execlp("./factorial", "factorial", NULL);
    perror("Exec error\n");
}

Fatorial.c

 int main(void){
   int i , result = 1, num = 1;
   read(0,&num,sizeof(int));
   printf("Numero recebido %d\n\n", num);   //Number its correct
   for (i = 1; i <= num; i++){
    result = result * i;  //Factorial ...
   }
   write(1,&result,sizeof(int));   //also tried the &result+1
   return 0;
 }

这是输出的例子：要计算的数量：4

   1
   2
   6
   24   /So fatorial.c receive the number correctly and calculate it

   PIPE: -1

正如你可以看到结果总是-1（声明的值）..所以我猜这个问题是它写在fatorial中。我错了吗？

PS：

   void cratePipe(int p[2]){
     int i; 
    if(pipe(p) == -1){
      perror("Pipe failed");
     }
   }

由于

C将其他程序的输出重定向到父

PS：

0 个答案: