Linux 如何将文件指针 ( FILE* fp ) 转换为文件描述符 (int fd)？
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How can I convert a file pointer ( FILE* fp ) to a file descriptor (int fd)?
提问by Phil Miller
I have a FILE *, returned by a call to fopen(). I need to get a file descriptor from it, to make calls like fsync(fd)on it. What's the function to get a file descriptor from a file pointer?
我有一个FILE *，通过调用返回fopen()。我需要从中获取一个文件描述符，以便对其进行调用fsync(fd)。从文件指针获取文件描述符的函数是什么？
采纳答案by Phil Miller
The proper function is int fileno(FILE *stream). It can be found in <stdio.h>, and is a POSIX standard but not standard C.
正确的函数是int fileno(FILE *stream)。它可以在 中找到<stdio.h>，并且是 POSIX 标准，但不是标准 C。
回答by Mark Gerolimatos
Even if fileno(FILE *)may return a file descriptor, be VERY careful not to bypass stdio's buffer. If there is buffer data (either read or unflushed write), reads/writes from the file descriptor might give you unexpected results.
即使fileno(FILE *)可能返回文件描述符，也要非常小心不要绕过 stdio 的缓冲区。如果有缓冲区数据（读取或未刷新的写入），则从文件描述符读取/写入可能会给您带来意想不到的结果。
To answer one of the side questions, to convert a file descriptor to a FILE pointer, use fdopen(3)
要回答附带问题之一，将文件描述符转换为 FILE 指针，请使用 fdopen(3)
