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[VC编程技巧]文件☞2.1EOF的误区
2014-11-23 17:45:00 】 浏览:3884
Tags:编程技巧 文件 2.1EOF 误区

编程的过程中,文件的操作是一个经常用到的问题,而关于EOF的理解大多人存在一个误区:“EOF--〉文件的结束符”!EOF是End Of File的缩写;在C语言中它是标准库stdio.h中定义的一个宏,而不是文件的结束符。

[cpp]
/***
*stdio.h - definitions/declarations for standard I/O routines
*
* Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
* This file defines the structures, values, macros, and functions
* used by the level 2 I/O ("standard I/O") routines.
* [ANSI/System V]
*
* [Public]
*
****/

#if _MSC_VER > 1000
#pragma once
#endif

#ifndef _INC_STDIO
#define _INC_STDIO
...
#define EOF (-1)
...

MSDN是这样说的:EOF is returned by an I/O routine when the end-of-file (or in some cases, an error) is encountered,即EOF是I/O操作遇到程序末尾或者是遇到错误时所返回的标志。所以说EOF不是文件中存在的内容,也就更谈不上文件结束符了。
当I/O操作返回EOF时,我们可以用函数foef()来判断I/O操作是否到达文件末尾,用函数ferror()来判断I/O操作是什么错误!

MSDN中函数foef():

[cpp]
int feof( FILE *stream );

Return Value

The feof function returns a nonzero value after the first read operation that attempts to read past the end of the file. It returns 0 if the current position is not end of file. There is no error return.

Parameter

stream

Pointer to FILE structure

Remarks

The feof routine (implemented both as a function and as a macro) determines whether the end ofstream has been reached. When end of file is reached, read operations return an end-of-file indicator until the stream is closed or untilrewind, fsetpos, fseek, or clearerr is called against it.


MSDN中函数ferror():

[cpp]
int ferror( FILE *stream );

Return Value

If no error has occurred on stream, ferror returns 0. Otherwise, it returns a nonzero value.

Parameter

stream

Pointer to FILE structure

Remarks

The ferror routine (implemented both as a function and as a macro) tests for a reading or writing error on the file associated withstream. If an error has occurred, the error indicator for the stream remains set until the stream is closed or rewound, or untilclearerr is called against it.



[VC编程技巧]文件☞2.1EOF的误区 https://www.cppentry.com/bencandy.php?fid=55&id=14403

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