fgetc的奇怪行为 [英] Strange behavior of fgetc

问题描述

我有一段代码，我在一些循环中执行，并希望得到具体的结果：

I have the block of code, which I execute in some cycle and expect to get concrete result:

代码： p>

The code:

fseek(file, start_seek_position, SEEK_SET);
cout << "Cursor befor fgetc: " << ftell(file) << endl;
fgetc(file);
cout << "Cursor after fgetc: " << ftell(file) << endl << endl;

期望：

Cursor befor fgetc: 76
Cursor after fgetc: 77

Cursor befor fgetc: 120
Cursor after fgetc: 121

Cursor befor fgetc: 170
Cursor after fgetc: 171

strong>实际结果：

Real result:

Cursor befor fgetc: 76
Cursor after fgetc: 44

Cursor befor fgetc: 120
Cursor after fgetc: 94

Cursor befor fgetc: 170
Cursor after fgetc: 151

为什么会发生这种情况？我认为 fgetc 应该将光标位置向前移动一个。

Why has this happened? I thought fgetc should move cursor position forward by one.

推荐答案

该文件在文本模式而不是二进制模式。因此代替：

The issue could be that you opened the file in text mode instead of binary mode. So instead of this:

file = fopen(file_name, "r"); // open as text

应该是这样：

#include <cstdio>
file = fopen(file_name, "rb"); // open as binary stream, not text

ftell 和 fseek 在作为二进制流打开的文件上始终如一地工作（更符合要求 - 正常工作）。

Functions such as ftell and fseek work consistently (more to the point -- behave as expected) on files opened as a binary stream.

但是，当文件作为文本流打开时（只需指定r，而不是rb），将会出现行结束和文件结束字符翻译，因此总是会抛开 fseek 和 ftell 工作。

However, when a file is opened as a text stream (just specifying "r" instead of "rb"), there will be end-of-line and end-of-file character translations occurring, thus invariably throwing off the way that fseek and ftell work.

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