如何使用C ++ 17获得以字节为单位的文件大小 [英] How to get the file size in bytes with C++17

问题描述

我应该知道特定操作系统是否存在陷阱吗？

Are there pitfalls for specific operating systems, I should know of?

有很多重复项（ 1 ， 2 ， 3 ， 4 ， 5 ）这个问题，但几十年前得到了回答。在许多这些问题中，投票率很高的答案今天是错误的。

There are many duplicates (1, 2, 3, 4, 5) of this question but they were answered decades ago. The very high voted answers in many of these questions are wrong today.

• stat.h （包装器 sprintstatf ），使用系统调用

• stat.h (wrapper sprintstatf), uses syscall

tellg（），根据定义返回一个位置，但不一定是字节。返回类型不是 int 。

tellg(), returns per definition a position but not necessarily bytes. The return type is not int.

推荐答案

< filesystem> （在C ++ 17中添加）使此非常简单。

<filesystem> (added in C++17) makes this very straightforward.

#include <cstdint>
#include <filesystem>

// ...

std::uintmax_t size = std::filesystem::file_size("c:\\foo\\bar.txt");

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如评论中所述，如果您正在计划要使用此功能确定要从文件中读取多少字节，请记住...

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As noted in comments, if you're planning to use this function to decide how many bytes to read from the file, keep in mind that...

...除非文件是由您独家打开的，它的大小可以在您请求它的时间和尝试从中读取数据的时间之间进行更改。

– Nicol Bolas

...unless the file is exclusively opened by you, its size can be changed between the time you ask for it and the time you try to read data from it.
– Nicol Bolas

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