fork() 之后管道的行为
在阅读《UNIX 环境中的高级编程》中有关管道的内容时，我注意到在分叉之后，父级可以 close() 管道的读取端，但它不会关闭子级的读取端。当进程分叉时，它的文件描述符会被保留吗？
我的意思是，在 fork 之前，管道读取文件描述符的保留计数为 1，而在 fork 之后为 2。当父进程关闭其读取端时，fd 变为 1 并为子进程保持打开状态。这本质上是正在发生的事情吗？常规文件描述符是否也会出现此行为？
When reading about pipes in Advanced Programming in the UNIX Environment, I noticed that after a fork the parent can close() the read end of a pipe and it doesn't close the read end for the child. When a process forks, does its file descriptors get retained?
What I mean by this is that before the fork the pipe read file descriptor had a retain count of 1, and after the fork 2. When the parent closed its read side the fd went to 1 and is kept open for the child. Is this essentially what is happening? Does this behavior also occur for regular file descriptors?
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正如人们可以在手册页上读到的有关 fork() 的内容：
所以是的，孩子拥有父母文件描述符的精确副本，并且引用了所有这些文件描述符，包括打开的文件。
As one can read on the man page about fork():
So yes, the child have exact copy of parent's file descriptors and that refers to all of them, including open files.
答案是肯定的（这同样适用于所有文件描述符，包括套接字之类的东西）。
在
fork()调用中，子进程获得每个文件描述符的自己单独的副本，每个文件描述符的行为就像它们是由dup()创建的一样。close()仅关闭传递的特定文件描述符 - 例如，如果您执行n2 = dup(n); close(n);，n引用的文件（管道、套接字、设备...）保持打开状态 - 这同样适用于由fork 复制的文件描述符()。The answer is yes, and yes (the same applies to all file descriptors, including things like sockets).
In a
fork()call, the child gets its own seperate copy of each file descriptor, that each act like they had been created bydup(). Aclose()only closes the specific file descriptor that was passed - so for example if you don2 = dup(n); close(n);, the file (pipe, socket, device...) thatnwas referring to remains open - the same applies to file descriptors duplicated by afork().是的，分叉会复制所有打开的文件描述符。
因此，对于一个典型的管道，一个 2 个槽数组（int fd[2]），父级和子级的 fd[0] 是相同的，fd[1] 也是如此。
您可以创建一个管道而无需分叉，并通过在一个进程中使用 fd[0] 和 fd[1] 来读取/写入自己。
Yes, a fork duplicates all open file descriptors.
So for a typical pipe, a 2 slot array (int fd[2]), fd[0] is the same for the parent and child, and so is fd[1].
You can create a pipe without forking at all, and read/write to yourself by using fd[0] and fd[1] in one process.