X-Recipient:	archive-cygwin AT delorie DOT com
DomainKey-Signature:	a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:cc:subject:in-reply-to:message-id
	:references:mime-version:content-type; q=dns; s=default; b=lJdiK
	Tv0Jb8gXAhnWlKh7U3Tn/o1KdV25Ra6IGPT/ibnRNFUJ2SGq82hoZYNz8sd2adeJ
	ZXxFyG+EZKwkgQxylRnkyKnYOwBP8+o0Z1B0BpUdgCERjYGTlHe6ms/xTLbMUJ9p
	jbF1cWbgWB7vLWTZVvZhQnaVXJIsLPmL1QyW/E=
DKIM-Signature:	v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:cc:subject:in-reply-to:message-id
	:references:mime-version:content-type; s=default; bh=RHrHZHu0T35
	SUIiYSsQDJ/Iox4k=; b=dP6/oWxiHcFA8sfEfF5gEwtq7AxtXoY/tmjfv/M+p0d
	g2Mc5KKT+fzm3n37Qo0GfEX/4U8Z8IdVmig1JD73L5aB3rimxJZCv7sl5CRCTOAo
	6h7HPSSZzI0w+7RTo/UNCrI/UVARQkR1csjd9KgoYgbTx5x+gozqnwBLFZh/ex0A
	=
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com
Authentication-Results:	sourceware.org; auth=none
X-Virus-Found:	No
X-Spam-SWARE-Status:	No, score=-0.7 required=5.0 tests=AWL,BAYES_00 autolearn=ham version=3.3.2
X-HELO:	mail.sciencetools.com
Date:	Wed, 12 Feb 2014 08:35:40 -0800 (PST)
From:	Richard <richard AT KarmannGhia DOT org>
To:	Ken Brown <kbrown AT cornell DOT edu>
cc:	cygwin AT cygwin DOT com
Subject:	Re: get rid of getpwent? (Was: cygwin-1.7.28 getpwent header declaration changes ?)
In-Reply-To:	<52FB9E51.7030607@cornell.edu>
Message-ID:	<alpine.LFD.2.03.1402120833480.24343@KarmannGhia.org>
References:	<31347914-BB4F-4039-984B-731B6C72F903 AT etr-usa DOT com> <52F7AEC5 DOT 5090205 AT tiscali DOT co DOT uk> <8B7B5FE0-7413-4358-BA8A-E0B6E0B17653 AT etr-usa DOT com> <52F8B50E DOT 7040307 AT lysator DOT liu DOT se> <52F92D58 DOT 9030408 AT etr-usa DOT com> <52F95D1D DOT 4050108 AT tiscali DOT co DOT uk> <4510121021 DOT 20140211062515 AT mtu-net DOT ru> <52FAB14C DOT 8060800 AT tiscali DOT co DOT uk> <52FABAF5 DOT 2060701 AT etr-usa DOT com> <52FAD730 DOT 9090507 AT redhat DOT com> <20140212090804 DOT GM2821 AT calimero DOT vinschen DOT de> <52FB9E51 DOT 7030607 AT cornell DOT edu>
User-Agent:	Alpine 2.03 (LFD 1266 2009-07-14)
MIME-Version:	1.0
X-IsSubscribed:	yes

On Wed, 12 Feb 2014, Ken Brown wrote:
> On 2/12/2014 4:08 AM, Corinna Vinschen wrote:
>> On Feb 11 19:06, Eric Blake wrote:
>>> On 02/11/2014 05:06 PM, Warren Young wrote:
>>>> On 2/11/2014 16:25, David Stacey wrote:
>>>>> getpwent() is called in three different places.
>>>> 
>>>> To those of you who have investigated these code paths: do any of them
>>>> look like they couldn't be replaced by getpwnam() or other calls that
>>>> would let cygwin1.dll do single-record AD/SAM lookups, rather than
>>>> whole-table/tree scans?
>>>> 
>>>> That is, do any of these programs really need to visit every record in
>>>> /etc/passwd?
>>> 
>>> libreadline wants to know how to tab-complete ~foo; to do that, it has
>>> to find all usernames beginning with foo.  How would you do that without
>>> visiting every single record?
>> 
>> This seems to be the major usage of getpwent these days.  The question
>> is, how bad is it if only a handful entries, or even only a single one
>> (of oneself) show up?
>> 
>> Either way, implementing a full getpwent requires to return the local
>> users, the users of the primary domain, and the users of all trusted
>> domains.  I know of domains with 200K users and there are probably
>> bigger ones.  How long should a search take when a user presses <TAB>
>> after the ~?  And then, shall the process running the getpwent actually
>> cache all of them?  This seems really excessive.
>
> What about the following compromise:  If /etc/passwd exists, then getpwent 
> behaves as it does currently.  Otherwise, it returns a handful of entries, or 
> possibly just the current user.  This gives users a choice.  If 
> tab-completion in this situation is important to them, they can keep their 
> /etc/passwd file.

Works for me! And I'd vote "just the current user" in lieu of "a handful" 
because even a handful has a huge overhead associated with it.

Richard

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

- Raw text -