Question

我正在尝试在Alpine Linux上使用文件魔术，并且每次导入AttributeError: Symbol not found: magic_open模块时，它都会magic爆炸。

我注意到有两个Python模块具有相同的magic名称空间，但是由于大多数Linux发行版似乎都在使用file-magic而不是python-magic，所以我决定制作我的模块取决于前者。但是在Alpine上，只有python-magic似乎可以工作：

设置Alpine并安装libmagic：

$ docker run --rm -it python:3-alpine /bin/sh
/ # apk add libmagic
fetch http://dl-cdn.alpinelinux.org/alpine/v3.8/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.8/community/x86_64/APKINDEX.tar.gz
(1/1) Installing libmagic (5.32-r0)
OK: 21 MiB in 35 packages

安装文件魔术师：

/ # pip install file-magic
Collecting file-magic
  Downloading https://files.pythonhosted.org/packages/bb/7e/b256e53a6558afd348387c3119dc4a1e3003d36030584a427168c8d72a7a/file_magic-0.4.0-py3-none-any.whl
Installing collected packages: file-magic
Successfully installed file-magic-0.4.0

但是它不起作用：

/ # python
Python 3.7.1 (default, Dec 21 2018, 03:21:42) 
[GCC 6.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import magic
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.7/site-packages/magic.py", line 61, in <module>
    _open = _libraries['magic'].magic_open
  File "/usr/local/lib/python3.7/ctypes/__init__.py", line 369, in __getattr__
    func = self.__getitem__(name)
  File "/usr/local/lib/python3.7/ctypes/__init__.py", line 374, in __getitem__
    func = self._FuncPtr((name_or_ordinal, self))
AttributeError: Symbol not found: magic_open
>>>

将文件魔术转换为python魔术：

$ pip uninstall file-magic
Uninstalling file-magic-0.4.0:
  Would remove:
    /usr/local/lib/python3.7/site-packages/file_magic-0.4.0.dist-info/*
    /usr/local/lib/python3.7/site-packages/magic.py
Proceed (y/n)? y
  Successfully uninstalled file-magic-0.4.0

/ # pip install python-magic
Collecting python-magic
  Downloading https://files.pythonhosted.org/packages/42/a1/76d30c79992e3750dac6790ce16f056f870d368ba142f83f75f694d93001/python_magic-0.4.15-py2.py3-none-any.whl
Installing collected packages: python-magic
Successfully installed python-magic-0.4.15

有效：

/ # python
Python 3.7.1 (default, Dec 21 2018, 03:21:42) 
[GCC 6.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import magic
>>>

我知道每个发行版都有其怪癖，我想适应，但是我现在不知道该怎么做。有没有一种方法可以定义模块的setup.py来解决这种情况？有没有办法调整Docker容器以处理文件魔术？在这种情况下正确的做法是什么？

Answer 1

Python-Magic在Alpine Linux上有a hard-coded fallback，因此您可能很难使用file-magic，它仅使用ctypes.util.find_library('magic')并且显然找不到您的库。

ctypes.util.find_library的确切行为是pretty complicated，但是如果您遍历代码并查看其尝试在平台上使用的方法，则可能会找到一种方法来找到它（可能是gcc，/sbin/ldconfig或objdump之一。

另一种解决方案是修补ctypes.py以正确处理Alpine之类的系统：

wget https://patch-diff.githubusercontent.com/raw/python/cpython/pull/10461.patch -O - | patch /usr/local/lib/python3.7/ctypes/util.py

现在，您只需要设置LD_LIBRARY_PATH，Python就可以找到该库：

/ # LD_LIBRARY_PATH="/usr/lib/" python -c "import ctypes.util; print(ctypes.util.find_library('magic'))"
libmagic.so.1

如何使文件魔术模块在Alpine Linux上运行？

1 个答案: