如何在使用fstream打开文件时截断文件 [英] How to truncate a file while it is open with fstream

问题描述

我知道可以使用

std::fstream fs(mypath, std::fstream::out | std::fstream::trunc);

但我需要读取文件，截断它，然后用相同的文件句柄（所以整个操作是原子的）。任何人？

but I need to read the file, truncate it, then write new contents all with the same file handle (so the whole operation is atomic). Anyone?

推荐答案

文件流不支持截断，除非打开文件。此外，操作不会是原子反正：至少，在POSIX系统上，你可以愉快地读取和写入已经由另一个进程打开的文件。

File streams don't support truncation except when opening a file. Also, the operations wouldn't be "atomic" anyway: at least, on POSIX systems you can happily read and write a file already opened by another process.

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