On 9/3/20, Greg Ewing <greg.ew...@canterbury.ac.nz> wrote:
> On 2/09/20 6:55 am, Eryk Sun wrote:
>> According to POSIX (st_dev, st_ino), it's the same directory, yet the
>> ".." entry evaluates depending on the path parsing context:
>>
>> >>> os.lstat('test1/spam/..').st_ino == os.lstat('test1').st_ino
>> True
>> >>> os.lstat('test2/spam/..').st_ino == os.lstat('test2').st_ino
>> True
>
> What happens if you go one level deeper? I.e. is
> os.lstat('test1/spam/eggs/../..').st_ino == os.lstat('test1').st_ino
> and
> os.lstat('test2/spam/eggs/../..').st_ino == os.lstat('test2').st_ino
> ?
Those two examples return true. Going a level deeper to 'spam/eggs'
doesn't change the behavior of the graft at "test2/spam".
An interesting case is bind mounting a directory on one of its child
directories. For example, if "spam" is mounted on "spam/mount_spam":
>>> s = os.lstat('spam/mount_spam/mount_spam/..')
>>> s.st_ino == os.lstat('spam').st_ino
True
The namespace graft only occurs at "spam/mount_spam". So
"spam/mount_spam/mount_spam" is the original filesystem directory, for
which the ".." entry references "spam". It's also consistent with
"spam/mount_spam" being bound to "spam".
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