os.stat() WindowsError 13 when file in use

[dcroberts]

BPO	1686475
Nosy	@loewis, @birkenfeld
Files	stat.diff

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/loewis'
closed_at = <Date 2007-04-30.01:54:06.000>
created_at = <Date 2007-03-23.02:31:29.000>
labels = ['library']
title = 'os.stat() WindowsError 13 when file in use'
updated_at = <Date 2007-04-30.01:54:06.000>
user = 'https://bugs.python.org/dcroberts'

bugs.python.org fields:

activity = <Date 2007-04-30.01:54:06.000>
actor = 'abkhd'
assignee = 'loewis'
closed = True
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2007-03-23.02:31:29.000>
creator = 'dcroberts'
dependencies = []
files = ['2329']
hgrepos = []
issue_num = 1686475
keywords = []
message_count = 7.0
messages = ['31627', '31628', '31629', '31630', '31631', '31632', '31633']
nosy_count = 4.0
nosy_names = ['loewis', 'georg.brandl', 'dcroberts', 'abkhd']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1686475'
versions = ['Python 2.5']

[dcroberts]

Using 2.5 Sept 19, 2006 on Windows XP, 32-bit.

os.stat() on an "in use" file (i.e., open by another process) erroneously returns WindowsError [Error 13]. The file stats should be available on an open file, even if you cannot read/write the file itself.

Python 2.4 correctly returns the stats on the file.

----------------

CORRECT in 2.4:
Python 2.4.4 (#71, Oct 18 2006, 08:34:43) [MSC v.1310 32 bit (Intel)] on win32
>>> import os
>>> os.stat('c:\\hiberfil.sys')
(33206, 0L, 2, 1, 0, 0, 804311040L, 1173962381, 1173962381, 1069302780)

-----------------
ERROR in 2.5:
Python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit (Intel)] on win32
>>> import os
>>> os.stat("c:\\hiberfil.sys")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
WindowsError: [Error 13] The process cannot access the file because it is being
used by another process: 'c:\\hiberfil.sys'

[birkenfeld]

May this be related to rev. 42230 - "Drop C library for stat/fstat on Windows." ?

[loewis]

It certainly is; Python is likely opening the file in the wrong mode now. I'll investigate, although contributions would be welcome.

[dcroberts]

Taking your hint, I just looked at the code in 42230 which uses the Win32 GetFileAttributesEx() function. This function does indeed return an error for an in-use file. Not sure if this is a "feature" or "bug" in the underlying Windows function. I did try FindFirstFile(), which is able to return info on an in-use file. Not sure if this is a reasonable alternative to GFAE(), but wanted to make folks aware of the possibility. It's probably slower, since it can handle wild-cards, and returns a handle for subsequent calls to FindNextFile(). The handle must be closed with FindClose(). I'm not sure what underlying mechanism FindFirstFile() uses, but I'm assuming it accesses the "directory" to get its information, rather than trying to access the file itself. FWIW.

[loewis]

Attached is a patch that makes it fall back to FindFirstFile if GetFileAttributesEx fail with ERROR_SHARING_VIOLATION.
File Added: stat.diff

[loewis]

I have now committed this patch as r54685 and r54686.

[abkhd]

Please see http://www.python.org/sf/1709112 for comment and patch.