Checking Linux Directory Permissions with Python

Question

I have an interesting scenario that I would like to get some expert advice on implementing. I have a Python application running on Linux that needs to return a single directory based upon group permissions.

For example, the Linux filesystem looks like this:

/Directory/Apple
/Directory/Beta
/Directory/Carotene

There is a group in /etc/group for Apple, Beta, and Carotene. Those group permissions are assigned to each directory (the Apple directory is only viewable/executable by members of the Apple group etc). A logged in user can only be a member of one group (Apple/Beta/Carotene), and I need to be able to figure out which directory the user has access to without throwing an exception. I can't use group membership calls inside of Python as the directory structure above is a remotely mounted filesystem.

So to simplify this: if the user is a member of the Beta group, I need to stat each subdir inside of /Directory and then return only a single path (in this example /Directory/Beta as the user is a member of the group directory).

I am thinking os.stat is a good way of doing this but I would like to see some other implementations if possible.

Thanks in advance!

Answer 1

To determine if a particular directory is accessible, use os.access .

os.access('/Directory/Apple', os.R_OK)

To check all of the immediate subdirs of /Directory , try this loop:

def find_my_group_directory():
  #UNTESTED
  root, dirs, _ = next(os.walk('/Directory'))
  for dir in dirs:
    if os.access(os.path.join(root, dir), os.R_OK):
      return os.path.join(root, dir)
  return None

Answer 2

It's easier to ask forgiveness than permission ( EAFP ). To check if a directory is accessible:

import os
def accessible(dir):
    try:
        os.listdir(dir)
    except OSError:
        return False
    return True
print(accessible('/root'))

To check if all the subdirs of a directory are permitted or not, apply this function in a for loop.