C++ 从 std::fstream 检索文件描述符
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/11558447/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Retrieving file descriptor from a std::fstream
提问by Abruzzo Forte e Gentile
Possible Duplicate:
Getting a FILE* from a std::fstream
可能的重复：
从 std::fstream 获取 FILE*
I am working on Linux and file descriptors are the main model in this OS.
我在 Linux 上工作，文件描述符是这个操作系统的主要模型。
I was wondering whether is there any library or any way to retrieve the native Linux file descriptor starting from a C++ std::fstream.
我想知道是否有任何库或任何方法可以从 C++ 开始检索本机 Linux 文件描述符std::fstream。
I thought about boost::iostreamsince there is a class called file_descriptorbut I understood that its purpose is different from the one I want to achieve.
我想过boost::iostream因为有一个类叫，file_descriptor但我明白它的目的和我想要实现的目的不同。
Do you know some way to do that?
你知道有什么方法可以做到吗？
采纳答案by Maxim Egorushkin
You can go the other way: implement your own stream buffer that wraps a file descriptor and then use it with iostreaminstead of fstream. Using Boost.Iostreamscan make the task easier.
您可以采用另一种方式：实现您自己的流缓冲区来包装文件描述符，然后使用它iostream代替fstream. 使用Boost.Iostreams可以使任务更容易。
Non-portable gcc solution is:
非便携式 gcc 解决方案是：
#include <ext/stdio_filebuf.h>
{
int fd = ...;
__gnu_cxx::stdio_filebuf<char> fd_file_buf{fd, std::ios_base::out | std::ios_base::binary};
std::ostream fd_stream{&fd_file_buf};
// Write into fd_stream.
// ...
// Flushes the stream and closes fd at scope exit.
}
回答by Hampus Nilsson
There is no (standard) way to extract the file number from an std::fstream since the standard library does not mandate how file streams will be implemented.
没有（标准）方法可以从 std::fstream 中提取文件编号，因为标准库不强制要求如何实现文件流。
Rather, you need to use the C file API if you want to do this (using FILE*).
相反，如果要执行此操作（使用FILE*），则需要使用 C 文件 API 。
回答by Some programmer dude
There is no official way to get the private file handle of a file stream (or actualy a std::basic_filebuf), just because it should be portable and discourage use of platform-specific functions.
没有官方的方法来获取文件流（或实际上 a std::basic_filebuf）的私有文件句柄，只是因为它应该是可移植的并且不鼓励使用特定于平台的功能。
However, you can do ugly hack like inheriting std::basic_filebufand from that try to pry out the file handle. It's not something I recommend though as it will probably break on different versions of the C++ library.
但是，您可以进行诸如继承之类的丑陋黑客攻击，std::basic_filebuf并从中尝试撬出文件句柄。这不是我推荐的东西，因为它可能会在不同版本的 C++ 库上中断。
回答by Artyom
There is no support of exposing file descriptor neither in standard C++ nor in libstdc++.
标准 C++ 和libstdc++.
