Ruby:如何获取文件锁定以进行写入? [英] Ruby: How to acquire file lock for writing?

问题描述

我想实现的是这样:

1. 如果其他某个进程正在持有该锁，请退出
2. 否则获取用于写的锁

我要修改的Ruby代码是

The Ruby code I am trying to modify is.

File.open(filename, "wb") { |inf|
  if inf.flock(File::LOCK_EX|File::LOCK_NB) == 0
    ...
  end
}

我可以找到的代码通常使用"rb".如果我更改为"wb"，则会出现问题:因为如果文件上有其他进程正在运行(除非尝试锁定，否则我无法知道)，该文件将被File.open(..., "wb")清除.

The codes I can find are usually using "rb". If I change to "wb", there is a problem: because if some other process is working on the file (which I cannot know until attempting the lock), the file will be wiped out by File.open(..., "wb").

有办法吗?谢谢.

我认为一种方法是使用"File::RDWR|File::CREAT"，这样您可以先打开文件，而不会擦除其内容，然后尝试锁定.不知道是否还有其他方法，但是"wb"可能无法工作.我想这是Ruby的尴尬:您必须先打开文件，然后才能获取锁.我认为这两个步骤应该原子化.

I think one way is to use "File::RDWR|File::CREAT", so that you can open file first and it won't wipe out its content, then try the lock. Not sure if there is other way, but "wb" probably will not work. I guess this is an awkwardness of Ruby: you have to open file first before acquiring the lock. I think these two steps should be made atomic.

推荐答案

创建一个锁定文件并将其锁定.如果您的filename说"path/to/file.txt"，请在"path/to/file.txt.lock"上创建一个锁.一旦获得了对锁定文件的锁定，请照常编辑真实文件.

Create a lock file and lock that instead. If your filename is say "path/to/file.txt" then create a lock on "path/to/file.txt.lock". Once you've acquired your lock on the lock file, edit the real file as normal.

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