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From: ebiederm@xmission.com (Eric W. Biederman)
To: Earl Chew <echew@ixiacom.com>
Cc: Ingo Molnar <mingo@elte.hu>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Andrew Morton <akpm@linux-foundation.org>,
	Eric Paris <eparis@redhat.com>,
	"Serge E. Hallyn" <serge.hallyn@canonical.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	<adobriyan@gmail.com>
Subject: Re: [PATCH] Support single byte reads from integers published in procfs by kernel/sysctl.c
Date: Mon, 23 Jan 2012 08:43:57 -0800	[thread overview]
Message-ID: <m1d3aanzci.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <m1mx9enzr0.fsf@fess.ebiederm.org> (Eric W. Biederman's message of "Mon, 23 Jan 2012 08:35:15 -0800")

ebiederm@xmission.com (Eric W. Biederman) writes:

>>
>> [ I also note that the patch allows multiple short reads (not necessarily
>>   just a single byte at a time) from these entries in procfs. ]
>>
>> I think there is a reasonable userspace expectation that entities
>> that present themselves as text files to produce results that are
>> consistent with the userspace model of a text file.
>>
>> For a more concrete example, consider the following BusyBox ash(1) code:
>>
>> read X < /proc/sys/kernel/threads-max
>> Y=$(cat /proc/sys/kernel/threads-max)
>>
>> read A < /proc/sys/kernel/core_pattern
>> B=$(cat /proc/sys/kernel/core_pattern)
>
>
>> The fact that these yield different results is surprising given that
>> the user sees these as text files.

To be precise /proc/sys/kernel/threads-max does not present itself as
an ordinary text file.  It reports that it's file length is 0 bytes
long.   That is different from an ordinary text file.

Eric

  reply	other threads:[~2012-01-23 16:41 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-22 18:46 [PATCH] Support single byte reads from integers published in procfs by kernel/sysctl.c Earl Chew
2012-01-23 14:47 ` Eric W. Biederman
2012-01-23 15:49   ` Earl Chew
2012-01-23 16:35     ` Eric W. Biederman
2012-01-23 16:43       ` Eric W. Biederman [this message]
2012-01-23 16:47       ` Earl Chew
2012-01-24 22:50         ` Andrew Morton
2012-01-25  6:28           ` Eric W. Biederman
2012-01-25 15:27           ` Earl Chew
2012-01-29 22:56         ` Earl Chew
2012-01-30  0:15           ` Eric W. Biederman
2012-01-30  1:13             ` Earl Chew

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