如何在 Python 中获取符号链接目标? [英] How to get symlink target in Python?

问题描述

使用 Python，我需要检查数百个符号链接是否正确，如果不正确，则重新创建它们.我现在要做的是比较我想要的和我拥有的真实路径，但它很慢，因为它是通过自动挂载的 NFS.

否则我将使用命令 'ls -l' 运行一个子进程并处理返回的字符串列表.我更喜欢更好的解决方案，使用 Python 库...

Edit1:我有:link_name ->link_target 然后 link_target ->a_real_file.我需要的是从 link_name 中提取 link_target，而不是 a_real_file.我不在乎真实文件是否存在.

Edit2: 可能是我表达的不对.我所说的正确符号链接是指向预定义路径的链接，即使它不存在".所以我需要检查一下:

link_name_1 ->目标_1link_name_2 ->目标_2

这就是为什么我需要提取目标，而不是真正的路径.然后我将它们与参考(字典)进行比较.所以我的问题是:如何提取目标路径?

解决方案

os.readlink() 的问题是它只能解决链接的 1 步.我们可能会遇到这样的情况，A 链接到另一个链接 B，而 B 链接悬空.

$ ln -s/tmp/example/notexist/tmp/example/B$ ln -s/tmp/example/B/tmp/example/A$ ls -l/tmp/示例->/tmp/示例/BB->/tmp/示例/不存在

现在在 Python 中，os.readlink 为您提供第一个目标.

<预><代码>>>>导入操作系统>>>os.readlink('A')'/tmp/示例/B'

但在大多数情况下，我认为我们对解析路径感兴趣.所以 pathlib 可以在这里提供帮助:

<预><代码>>>>从 pathlib 导入路径>>>路径('A').resolve()PosixPath('/tmp/example/notexist')

对于较旧的 Python 版本:

<预><代码>>>>os.path.realpath('A')'/tmp/示例/不存在'

Using Python, I need to check whether hundreds of symlinks are correct and recreate them when not. What I do now is to compare real paths of what I want and what I have, but it's slow because it's over NFS with an automount.

Otherwise I'm going to run a subprocess with the command 'ls -l' and work on the list of strings returned. I would prefer a better solution, using a Python library...

Edit1: I have: link_name -> link_target and then link_target -> a_real_file. What I need is to extract link_target from link_name, not a_real_file. I don't care if the real file does not exist.

Edit2: Maybe I did not express correctly. What I mean by a correct symlink is 'a link that point to a predefined path, even if it does not exist'. So I need to check that:

link_name_1 -> target_1
link_name_2 -> target_2

That's why I need to extract targets, not the real paths. Then I compare them to a reference (dictionary). So my question is: How do I extract the target path?

解决方案

The problem with os.readlink() is it will only resolve 1 step of the link. We can have a situation where A links to another link B, and B link is dangling.

$ ln -s /tmp/example/notexist /tmp/example/B
$ ln -s /tmp/example/B /tmp/example/A
$ ls -l /tmp/example
A -> /tmp/example/B
B -> /tmp/example/notexist

Now in Python, os.readlink gives you the first target.

>>> import os
>>> os.readlink('A')
'/tmp/example/B'

But in most situations I assume we are interested in the resolved path. So pathlib can help here:

>>> from pathlib import Path
>>> Path('A').resolve()
PosixPath('/tmp/example/notexist')

For older Python versions:

>>> os.path.realpath('A')
'/tmp/example/notexist'

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