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Re: cp(1) fails to copy file from /proc
From: |
Mike Frysinger |
Subject: |
Re: cp(1) fails to copy file from /proc |
Date: |
Sat, 18 Apr 2009 17:16:11 -0400 |
User-agent: |
KMail/1.11.1 (Linux/2.6.28; KDE/4.2.1; x86_64; ; ) |
On Saturday 18 April 2009 16:58:52 Jim Meyering wrote:
> Mike Frysinger wrote:
> > On Friday 17 April 2009 18:28:07 James Youngman wrote:
> >> The patch itself looks good, but it might be worth leaving in a
> >> comment indicating why the optimisation should not be reintroduced...
> >
> > and/or a new test (i prefer the "and"):
> > if [ -e /proc/cpuinfo ] ; then
> > cp /proc/cpuinfo cpuinfo.cp
> > cat /proc/cpuinfo > cpuinfo.cat
> > cmp cpuinfo.cp cpuinfo.cat
> > fi
>
> Of course ;-)
> As promised, I've added a test for this below.
>
> We can't use /proc/cpuinfo, at least not precisely like that,
> because its cpu speed line can change due to frequency scaling.
> Also, that file is usually too small to trigger the failure.
hmm, i seem to remember cpuinfo being a pita when doing remote `ssh cp ...`,
but must have been some other file. you got the idea at any rate :).
> Here's a more complete patch, with a title and NEWS reflecting
> that I now think it's a linux kernel bug.
i think that characterization is incorrect. POSIX certainly states that a
read value smaller than what was requested is not an error in and of itself.
i havent looked at the kernel internals as to why this occurs, but if i had to
make a guess, it's related to the seq_file stuff as a common helper in place
of many common buggy procfs implementations. and in that case, the current
behavior is to be expected.
-mike
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- cp(1) fails to copy file from /proc, Jukka Salmi, 2009/04/16
- Re: cp(1) fails to copy file from /proc, Jim Meyering, 2009/04/16
- Re: cp(1) fails to copy file from /proc, Jim Meyering, 2009/04/16
- Re: cp(1) fails to copy file from /proc, James Youngman, 2009/04/17
- Re: cp(1) fails to copy file from /proc, Jim Meyering, 2009/04/17
- Re: cp(1) fails to copy file from /proc, James Youngman, 2009/04/17
- Re: cp(1) fails to copy file from /proc, Mike Frysinger, 2009/04/18
- Re: cp(1) fails to copy file from /proc, Jim Meyering, 2009/04/18
- Re: cp(1) fails to copy file from /proc,
Mike Frysinger <=
- Re: cp(1) fails to copy file from /proc, Jim Meyering, 2009/04/18
- Re: cp(1) fails to copy file from /proc, Andreas Schwab, 2009/04/19
- Re: cp(1) fails to copy file from /proc, Jim Meyering, 2009/04/19
- Re: cp(1) fails to copy file from /proc, James Youngman, 2009/04/19
- Re: cp(1) fails to copy file from /proc, Jim Meyering, 2009/04/23
- Re: cp(1) fails to copy file from /proc, Mike Frysinger, 2009/04/26