在Linux上以原子方式交换两个文件的内容

问题描述：

我有两个文件A和B，每个文件都有自己的内容.

I have two files, A and B, each with its own content.

我想交换这两个文件，所以A会变成B，而B会变成A.但是我想做一个保证，没有其他进程会发现这两个文件处于不一致状态，也没有任何进程会发现其中的任何文件丢失，即使是很短的时间.因此，作为附带的操作，我还要保证，如果在操作过程中发生任何错误，则什么都不会改变(我想这就像一笔交易).

I would like to swap these two files, so A would become B, and B would become A. But I would like to do with a guaranty that no other process will find these two files in an inconsistent state, nor any process will find any of those files missing, even for a short while. So, as a side operation, I would also like to have a guaranty that if anything would go wrong during the operation, nothing will be changed (kind of like a transaction I guess).

在OS X上有一个exchangedata()函数，所以我想我正在寻找与之等效的Linux，或者至少是进行原子文件交换的等效方法.

On OS X there is a exchangedata() function, so I guess I'm looking for a Linux equivalent of it, or at least an equivalent method for doing atomic file swap.

答

您可以使用(相当新的) linux syscall renameat2

You can use the (fairly recent) linux syscall renameat2

这是定义:

int renameat2(int olddir, const char *oldname, 
      int newdir, const char *newname, unsigned int flags);

您可以在

You can find its source code on the kernel's Git repo if needed.

它与renameat基本上相同，但是如果传递标志RENAME_EXCHANGE，它将交换两个文件，而不是将一个文件重命名为另一个文件.

It's basically the same as renameat, but if you pass the flag RENAME_EXCHANGE it will swap the two files instead of renaming one into the other.

该操作是原子操作.

在Linux上以原子方式交换两个文件的内容

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