我想知道结构文件的内部成员，最新游戏 [英] I Wanna know the Internal Members of struct FILE, the latest ones
问题描述
当我读到K＆放C编程语言的pg.176; R，我感到非常兴奋。我发现结构文件的所有成员（我正在寻找）和它只是真棒知道事情是如何工作的。但细想一下，GCC抱怨，错误：FILE没有名为成员的fd。这意味着，现在事情已经改变了，我用Google搜索，但没有找到。请帮帮忙，谢谢你在前进。
我可以使用的fileno（）来获取的文件描述符，但我讨厌在抽象层面的工作。
INT
主（INT ARGC，字符** argv的）{ FILE *计划生育=的fopen（CT.C，R）;
的printf（％i的，FP-GT＆; FD）; 返回0;
}
您需要在你的C库的源$ C $ C的样子。
既然你提到的gcc和Linux，你可能使用GNU libc的，这当然是免费的软件。
<一个href=\"http://sourceware.org/git/?p=glibc.git;a=blob;f=libio/stdio.h;h=754301fc1abd789700a723fa399fecd3f931dfa2;hb=HEAD\">This文件说：
/ *不透明型流。这是在其他地方使用的定义。 * /
typedef结构_IO_FILE __FILE;
和<一个href=\"http://sourceware.org/git/?p=glibc.git;a=blob;f=libio/libio.h;h=3cf1712ea98d3c253f418feb1ef881c4a44649d5;hb=HEAD#l245\">this文件声明 _IO_FILE 结构：
结构_IO_FILE {
INT _flags; / *高位字是_IO_MAGIC;剩下的就是标志。 * /
＃定义_IO_file_flags _flags / *下面的指针对应于C ++流缓冲协议。 * /
/ *注：Tk的直接使用_IO_read_ptr和_IO_read_end字段。 * /
字符* _IO_read_ptr; / *当前读指针* /
字符* _IO_read_end; / *获取区域的结束。 * /
字符* _IO_read_base; / *补篮开始+送面积。 * /
字符* _IO_write_base; / *放区的开始。 * /
字符* _IO_write_ptr; / *当前放指针。 * /
字符* _IO_write_end; / *放区结束。 * /
字符* _IO_buf_base; / *保留区启动。 * /
字符* _IO_buf_end; / *预留区结束。 * /
/ *以下字段用于支持备份和还原。 * /
字符* _IO_save_base; / *指针开始非流动GET区。 * /
字符* _IO_backup_base; / *指向备份区的第一个有效字符* /
字符* _IO_save_end; / *指针结束非流动GET区。 * / 结构_IO_marker * _markers; 结构_IO_FILE * _chain; INT _fileno;
＃如果0
INT _blksize;
＃其他
INT _flags2;
＃万一
_IO_off_t _old_offset; / *这个曾经被_offset但它太小了。 * /＃定义__HAVE_COLUMN / * *临时/
PBASE的/ * 1 +柱号码（）; 0是未知的。 * /
无符号短_cur_column;
符号字符_vtable_offset;
烧焦_shortbuf [1]; / *字符* _save_gptr;字符* _save_egptr; * / _IO_lock_t * _lock;
#IFDEF _IO_USE_OLD_IO_FILE
};
机会是，上述，从一个真正的产品质量图书馆来了，稍微比K＆放大器使用的例子更加复杂; R。而且，当然，你不能的使用的这个，因为它是图书馆内部和文件是一个不透明的类型，就像它说。
When I read pg.176 of The C programming Language by K&R, I was very excited. I found all the members of struct FILE ( which I was searching for ) and its just awesome to know how things work. But guess what, gcc complains, error: ‘FILE’ has no member named ‘fd’. It means things have changed now, I googled but could not find. Please Help, Thank you in advance.
I can use fileno() to get the file descriptor, but I hate working on abstraction level.
int
main ( int argc, char **argv ){
FILE *fp = fopen ("ct.c", "r");
printf ("%i", fp->fd);
return 0;
}
You need to look in your C library's source code.
Since you mention gcc and Linux, you're probably using the GNU libc, which is of course free software.
This file says:
/* The opaque type of streams. This is the definition used elsewhere. */
typedef struct _IO_FILE __FILE;
And this file declares the _IO_FILE structure:
struct _IO_FILE {
int _flags; /* High-order word is _IO_MAGIC; rest is flags. */
#define _IO_file_flags _flags
/* The following pointers correspond to the C++ streambuf protocol. */
/* Note: Tk uses the _IO_read_ptr and _IO_read_end fields directly. */
char* _IO_read_ptr; /* Current read pointer */
char* _IO_read_end; /* End of get area. */
char* _IO_read_base; /* Start of putback+get area. */
char* _IO_write_base; /* Start of put area. */
char* _IO_write_ptr; /* Current put pointer. */
char* _IO_write_end; /* End of put area. */
char* _IO_buf_base; /* Start of reserve area. */
char* _IO_buf_end; /* End of reserve area. */
/* The following fields are used to support backing up and undo. */
char *_IO_save_base; /* Pointer to start of non-current get area. */
char *_IO_backup_base; /* Pointer to first valid character of backup area */
char *_IO_save_end; /* Pointer to end of non-current get area. */
struct _IO_marker *_markers;
struct _IO_FILE *_chain;
int _fileno;
#if 0
int _blksize;
#else
int _flags2;
#endif
_IO_off_t _old_offset; /* This used to be _offset but it's too small. */
#define __HAVE_COLUMN /* temporary */
/* 1+column number of pbase(); 0 is unknown. */
unsigned short _cur_column;
signed char _vtable_offset;
char _shortbuf[1];
/* char* _save_gptr; char* _save_egptr; */
_IO_lock_t *_lock;
#ifdef _IO_USE_OLD_IO_FILE
};
Chances are that the above, coming from a "real" production-quality library, is slightly more complicated than the example used in K&R. And, of course, you can't use this since it's library-internal and FILE is an opaque type, just as it says.
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