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Message-ID: <50F417F9.8040108@shaddybaddah.name>
Date: Tue, 15 Jan 2013 01:36:41 +1100
From: Shaddy Baddah <lithium-cygwin AT shaddybaddah DOT name>
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To: cygwin AT cygwin DOT com
Subject: Re: stat() and tilde prefix (was bad bash tab completion)
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Hi,

On 14/01/13 21:00, Corinna Vinschen wrote:
> On Jan 14 01:17, Christopher Faylor wrote:
>> On Mon, Jan 14, 2013 at 04:21:25PM +1100, Shaddy Baddah wrote:
>>> In investigating this, I believe the issue I am having is due to how
>>> stat() handles tilde prefixed paths. On linux we see:
>>>
>>> linux$ $ python -c 'import os; print os.stat("~/..")'
>>> Traceback (most recent call last):
>>>    File "<string>", line 1, in<module>
>>> OSError: [Errno 2] No such file or directory: '~/..'
>>>
>>> and on cygwin we see:
>>>
>>> cygwin$ python -c 'import os; print os.stat("~/..")'
>>> posix.stat_result(st_mode=16832, st_ino=562949953496729L,
>>> st_dev=4174909669L, st_nlink=1, st_uid=42037, st_gid=10513, st_size=0L,
>>> st_atime=1357616166, st_mtime=1357616166, st_ctime=1357616166)
>>
>> It is a bug.  It's not just "~".  Any nonexistent directory will
>> work, like "foo/..".
>
> And it's a bug which isn't easily fixed.  Since about the dawn of time,
> Cygwin's core path handling evaluates the path in a non-POSIX manner,
> mainly for performance reasons.

Thank you both for your explanations. If my understanding is correct,
stat() will be returning for the current working directory.

It seems to me then that a patch to bash may be in order? I can see how
the bash check is the right thing to do. It doesn't want the special
tilde expansion to mask and disallow referencing of real tilde prefixed
paths. So the stat() check is the quick win to determine that.

 From what I make of it, there needs to be a patch that, although can
work generically, adds checks only required for Cygwin. And therefore
is specific to the Cygwin package.

The check would be an extension of the file_exists() function, perhaps
called tilde_file_exists(), which determines if the tilde prefix forms
a directory component of the path (strchr('/')?). If it does not, the
file_exists() check is sufficient. If it does, then the check of if
that directory exists is logically and'ed to the result of
file_exists().

Does that sound about right?

-- 
Regards,
Shaddy

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