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Date: Thu, 08 Dec 2005 07:20:23 -0700
From: Eric Blake <ebb9 AT byu DOT net>
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Subject: Re: Error reported dd'ing close of end of block device with skip
References: <E05F1FD208D5AA45B78B3983479ECF0856C0F9 AT saturn DOT p3corpnet DOT pivot3 DOT com> <20051208103033 DOT GA30538 AT calimero DOT vinschen DOT de>
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According to Corinna Vinschen on 12/8/2005 3:30 AM:
> 
> Hey, cool idea!  There's no definition of O_DIRECT in Cygwin so far, but
> this sounds like a worthwhile extension, at least for disk and tape
> devices, but maybe also for files.  This won't be in the next Cygwin
> version 1.5.19, probably, but I'll certainly implement that for 1.5.20.

Another cool flag is newer Linux's O_NOATIME, which inhibits updating the
access time.  In particular, coreutils CVS has already added a -noatime
option to dd (a nop unless the system supports it), and is considering
moving to using O_NOATIME on directories for ls and other traversal
routines, since POSIX allows ls to not change directory atime during
traversal, and since listing directories is effectively a read-only
operation that doesn't really need to write to disk just to update the
directory atimes.  If Windows FILE_FLAG_BACKUP_SEMANTICS can be used to
avoid touching the atime, then this flag seems useful to implement for the
1.5.20 timeframe.

While we are talking about wishes, Solaris and newer glibc provide the *at
family of functions (such as openat); the cool thing about these functions
is that they provide the ability to make directory traversal reentrant
since with fd-relative semantics you no longer need to call chdir().  See
for example
http://lists.gnu.org/archive/html/bug-gnulib/2005-11/msg00042.html.

- --
Life is short - so eat dessert first!

Eric Blake             ebb9 AT byu DOT net
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