strange interaction between open and cwd

[Cameron Simpson]

On 03May2010 15:23, Baz Walter <bazwal at ftml.net> wrote:
| On 03/05/10 14:46, Peter Otten wrote:
| >Baz Walter wrote:
| >
| >>attempting to remove the cwd would produce an error). but how can python
| >>determine the parent directory of a directory that no longer exists?
| >
| >My tentative explanation would be that the directory, namely the inode,
| >still exists -- only the entry for it in its parent directory is gone.
| >
| >So "one level up from here" is still a valid operation, but there is no
| >longer a path in the file system associated with "here".
| 
| so "here" must always be available somehow, even if getcwd() fails

Well, yeah. Just like an open file handle on a file you have subsequently
removed still exists. Remember that the directory tree is a digraph, and
(historically at least, and probably for real in many filesystems) '.' and
'..' are just pointers to "here" and "up".

Your rmdir has detached the current directory from the one that was
"up", but the "up" pointer still references the old parent.

There's just no filesystem path that refers to your current directory
any more (except '.'). Just like a detached object in python really.

Cheers,
-- 
Cameron Simpson <cs at zip.com.au> DoD#743
http://www.cskk.ezoshosting.com/cs/

Everything that can be invented has been invented.
        - Charles H. Duell, Commissioner, U.S. Office of Patents, 1899.