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Date: Fri, 13 Jul 2007 17:58:55 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: if [ -w branching: how to spot a locked USB stick
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On Jul 13 10:27, Christopher Faylor wrote:
> On Fri, Jul 13, 2007 at 04:15:26PM +0200, Corinna Vinschen wrote:
> >On Jul 13 08:00, Eric Blake wrote:
> >> According to Corinna Vinschen on 7/13/2007 7:06 AM:
> >> >> Actually, this is a cygwin question.  Bash's [ command only reports what
> >> >> access("/h",W_OK) tells it to report, 
> >> > 
> >> > It's the latter.  The fact that the USB stick is locked doesn't
> >> > mean that the permission bits returned by the OS calls are augmented
> >> > to reflect the fact that the stick is not writable.  All permission
> >> > bits are still intact.  Only when actually trying to write to the device,
> >> > you'll get the Win32 error message equivalent of EROFS.
> >> 
> >> But POSIX requires access(...,W_OK) to fail with EROFS on a read-only file
> >> system.  Is there any way for cygwin to easily determine this without
> >> actually attempting a write?
> >
> >Not that I'm aware of.  I added this to my TODO list.  However, as
> >usual, http://cygwin.com/acronyms/#PTC.
> 
> Why do I see another bullet item for the "Why is cygwin so slow" discussion
> here?

Actually I found that there's a laughable simple way to determine a
read-only device.  When calling GetVolumeInformation, the
FILE_READ_ONLY_VOLUME flag is set.  I just tested this with a USB
stick.  Since we have the information from fs_info anyway, a fix
should be very simple and not affect Cygwin's spee^Wslowness.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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