Message 61545 - Python tracker

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Author	loewis
Recipients	Piffen, christian.heimes, kbk, loewis, richjtd
Date	2008-01-22.22:38:10
SpamBayes Score	0.06928253
Marked as misclassified	No
Message-id	<1201041492.71.0.488717213985.issue1743@psf.upfronthosting.co.za>
In-reply-to

Content
I've studied the problem with Process Monitor. If a file is hidden, open(f, "w") fails, whereas os.open(f, os.W_OK\|os.O_CREAT) succeeds. In the succeeding call, process monitor reports Desired Access: Generic Read/Write Disposition: OpenIf Options: Synchronous IO Non-Alert, Non-Directory File Attributes: N ShareMode: Read, Write AllocationSize: 0 OpenResult: Opened In the failing call, it reports Desired Access: Generic Write, Read Attributes Disposition: OverwriteIf Options: Synchronous IO Non-Alert, Non-Directory File Attributes: N ShareMode: Read, Write AllocationSize: 0 I then tried os.open(f, os.W_OK\|os.CREAT\|os.O_TRUNC) which also fails, giving Desired Access: Generic Read/Write Disposition: OverwriteIf Options: Synchronous IO Non-Alert, Non-Directory File Attributes: N ShareMode: Read, Write AllocationSize: 0 So it fails for FILE_OVERWRITE_IF, but succeeds for FILE_OPEN_IF. These map back to CREATE_ALWAYS and OPEN_ALWAYS - apparently, you can't truncate a hidden file on Vista.

I've studied the problem with Process Monitor. If a file is hidden,
open(f, "w") fails, whereas os.open(f, os.W_OK|os.O_CREAT) succeeds.

In the succeeding call, process monitor reports

Desired Access:	Generic Read/Write
Disposition:	OpenIf
Options:	Synchronous IO Non-Alert, Non-Directory File
Attributes:	N
ShareMode:	Read, Write
AllocationSize:	0
OpenResult:	Opened

In the failing call, it reports

Desired Access:	Generic Write, Read Attributes
Disposition:	OverwriteIf
Options:	Synchronous IO Non-Alert, Non-Directory File
Attributes:	N
ShareMode:	Read, Write
AllocationSize:	0

I then tried os.open(f, os.W_OK|os.CREAT|os.O_TRUNC) which also fails,
giving

Desired Access:	Generic Read/Write
Disposition:	OverwriteIf
Options:	Synchronous IO Non-Alert, Non-Directory File
Attributes:	N
ShareMode:	Read, Write
AllocationSize:	0

So it fails for FILE_OVERWRITE_IF, but succeeds for FILE_OPEN_IF. These 
map back to CREATE_ALWAYS and OPEN_ALWAYS - apparently, you can't 
truncate a hidden file on Vista.

History
Date	User	Action	Args
2008-01-22 22:38:13	loewis	set	spambayes_score: 0.0692825 -> 0.06928253 recipients: + loewis, kbk, christian.heimes, richjtd, Piffen
2008-01-22 22:38:12	loewis	set	spambayes_score: 0.0692825 -> 0.0692825 messageid: <1201041492.71.0.488717213985.issue1743@psf.upfronthosting.co.za>
2008-01-22 22:38:11	loewis	link	issue1743 messages
2008-01-22 22:38:10	loewis	create