我正在做一个小程序，我不得不做了一段时间前，我想缩短它。
这个小程序是关于一个线程创建几个子线程，这些子线程按照顺序将其标准输出/输入重定向到另一个线程，除了最后一个子线程，后者不会像这样重定向其标准输出。
Parent pipe child1 pipe child2 pipe last child
__ __ __
O-----|__|-----O-----|__|-----O-----|__|-----O -> Stdout
当我第一次面对这段代码时，我制作了一个维度为[núchild][2]的矩阵，并从该矩阵的每个位置制作了一个管道，因此在需要时很容易将每个管道连接到每个孩子。但现在我只想用两根管子，用继承来“玩”。
也许我并没有很好地解释自己，所以我想用我的代码可以更好地理解所有事情，所以我们开始吧。
piping_function(int number_of_child){
int i;
int olddesc[2];
int newdesc[2]; //Here I create the descriptors of the pipes I'll use
int *olddir;
int *newdir;
if(pipe(olddesc)<0 || pipe(newdesc) < 0){ //I create the pipes
//Error
}
olddir = olddesc;
newdir = newdesc; //And attach the directions to the array's direction (we will see later why)
for(i = 0; i < number_of_child; i++){
chaddr[i] = fork();
switch(chaddr[i]){
case -1:
//Error trace
case 0:
dup2(olddesc[0],0); //Here I redirect the pipe who connect the previous child's pipe to the standard input
if(i != number_of_child - 1)
dup2(newdesc[1],1); //And here, except from the last child, I redirect the standard output to the pipe who will connect to the standard input of the next child
close(olddesc[0]);
close(newdesc[1]); //I close the descriptors I don't need
//Several child operations with standard input-output (end up returning 0/1 after the pipeline is connected, so no child will create any child)
default:
if(i == 0)
dup2(olddesc[1], 1); //I want the standard output of the principal proccess only on the first pipe
olddir = newdir; //Here I would want the direction of the "old" pipe to be the direction of the "new" pipe, in order to achieve the pipeline
if(pipe(newdesc)<0)
//Error
break;
}//End of switch
}//End of for
close(olddesc[0]);close(olddesc[1]);close(newdesc[0]);close(newdesc[1]); //I don't need these descriptors anymore, as they must be redirected to the standard's input/output of the process they need.
}//End of function
好吧，这是我的密码。我想我可以看到我做的错误，当我把olddir变成newdir，并创建管道时，我做olddir也是那个新管道，对吧？所以我的问题来了：
有什么办法实现这一改变吗？我是说，我想要的是等于olddir（谁是olddesc的地址，对吧？所以如果我改变地址，olddesc的地址也会改变，对吧？）对于newdir，为了继续使用我之前创建的管道来重定向“next”子级的标准输出，但是我也希望newdir是一个新管道。
我真的不知道我解释的对不对，我不是一个母语者，用其他语言解释这些想法有点困难。请随意纠正语法错误，我会很感激的，并问任何关于代码的问题，因为也许我没有给出我想要的观点。
谢谢。
最佳答案
好吧，我终于做到了，但是改变了视角，不做任何地址覆盖的工作，只玩迭代，以便始终保持两个管道之一的记录。我没有真正解决地址问题，但它是这样工作的，我很满意。
piping_function(int number_of_child){
int i;
int olddesc[2];
int newdesc[2]; //Here I create the descriptors of the pipes I'll use
//Now we'll start from the last pipe, so we can connect the parent to the first one and not connect the last child's output.
for(i = number_of_child - 1; i >= 0; i--){
//Instead of changing addresses, I'll play with the "i"
if(i%2==0){
close(newdesc[0]); //We close the last descriptors
close(newdesc[1]);
pipe(newdesc); //And create a new pipe!
}
else{
close(olddesc[0]);
close(olddesc[1]);
pipe(oldesc);
}
chaddr[i] = fork();
switch(chaddr[i]){
case -1:
//Error trace
case 0:
if(i%2==0){
dup2(newdesc[0],0); //Here I redirect the pipe who connect the previous child's pipe to the standard input
if(i != number_of_child - 1)
dup2(olddesc[1],1); //And here, except from the last child, I redirect the standard output to the pipe who will connect to the standard input of the next child
close(newdesc[1]);
close(olddesc[0]); //I close the descriptors I don't need
}
else{
dup2(olddesc[0],0); //Here I redirect the pipe who connect the previous child's pipe to the standard input
if(i != number_of_child - 1)
dup2(newdesc[1],1); //And here, except from the last child, I redirect the standard output to the pipe who will connect to the standard input of the next child
close(olddesc[1]);
close(newdesc[0]); //I close the descriptors I don't need
}
//Several child operations with standard input-output (end up exiting 0/1 after the pipeline is connected, so no child will create any child)
default:
if(i == 0)
dup2(newdesc[1], 1); //I want the standard output of the principal proccess only on the first pipe
break;
}//End of switch
}//End of for
close(olddesc[0]);close(olddesc[1]);close(newdesc[0]);close(newdesc[1]); //I don't need these descriptors anymore, as they must be redirected to the standard's input/output of the process they need.
}//End of function
*编辑：
我不认为总是关闭描述符是好的，即使没有创建任何东西，我看到我在这段代码中这样留下了它们，但是为了让它正常工作，我们应该只在创建时关闭描述符，这样每次关闭都需要一个if。