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X-WM-Posted-At:	avacado.atomice.net; Thu, 9 May 02 21:39:30 +0100
Message-ID:	<04e801c1f799$9e7354e0$0100a8c0@advent02>
From:	"Chris January" <chris AT atomice DOT net>
To:	<cygwin AT cygwin DOT com>
References:	<3CDAD4F4 DOT BC86A5BA AT cistron DOT nl>
Subject:	Re: EISDIR EACCES and open in grep
Date:	Thu, 9 May 2002 21:39:30 +0100
MIME-Version:	1.0
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> I have been trying to chase the same problem (grep -R does not
> work on W9x) during the last few days.
> On WNT/W2K/XP the code works because CreateFile is called with
> the FILE_FLAG_BACKUP_SEMANTICS bit set in file_attributes
> (lines 371,372 in fhandler.cc).
> On W9x you just get Permission Denied (EACCESS).
> MSDN documents that opening directories this way is only supported
> on WNT/W2K/XP.
>
> The branch taken in the code is *not* the
> 'if (GetLastError () == ERROR_INVALID_HANDLE)'
> but the 'else __seterrno ();', which sets EACCESS.
> Found that by tracing with gdb through a debug version
> of cygwin1.dll while running 'grep -R'.
> So I believe your fix is applied to the wrong branch
> of the if statement.
> Probably the fix should also be guarded with a check for W9x.
>
> Related to this:
> What is the precise semantics for open(2), read(2) on directories
> in POSIX?
> Or in other words, if open(2) on a dir succeeds what should read(2)
> on a directory do ?
See: http://www.opengroup.org/onlinepubs/007908799/xsh/read.html
Assuming the only error is trying to read form the directory, it should
return:
[EISDIR]
The fildes argument refers to a directory and the implementation does not
allow the directory to be read using read(), pread() or readv(). The
readdir() function should be used instead.

EINVAL is probably the best error to return from open() if the system
doesn't support opening of directories.

Chris



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