unlink()'s not quite POSIX behavior.

Joe Smith unknown_kev_cat@hotmail.com
Tue Jul 31 19:17:00 GMT 2007

It appears that currently unlink will not immedately remove a file (that has 
only one link) if a handle to the file is open, but will flag it for 
deletion once the file handle closes.

This is causing a problem with Python 3000.

POSIX says:

>When the file's link count becomes 0 and no process has the file open,
>the space occupied by the file shall be freed and the file shall no longer
>be accessible. If one or more processes have the file open when the last
>link is removed, the link shall be removed before unlink() returns, but
>the removal of the file contents shall be postponed until all references
>to the file are closed.

Windows NT had a design goal of allowing a complient implementation
of POSIX to be implmented in a subsystem (along with userespace utilities).
(Hence services for unix).

Could we at least simulate the behavior by moving the file out of the way 
(simultaionsly renaming it to something unique),
and forcing it into the delqueue? (by Setting the 
FILE_DISPOSITION_INFORMATION's DeleteFile flag to true?)

Wait a moment, that looks to be exactly what unlink_nt is doing?
What is going on?

(The problem is with a call in Python3k getting a "Permission denied" (ERRNO 
13) error when attempting to create a file shortly after it has been deleted 
with unlink. That seems to be consistant with standard windows behavior for 
deleting a file, as trying to create it again before the last handle is 
closed would return an ERROR_ACCESS_DENIED.)

However, it looks like with unlink_nt that should not be happening, right?

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