Message-ID: <4CE2A56C.4080407@fifthhorseman.net>
Date: Tue, 16 Nov 2010 10:38:20 -0500
From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
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To: Jameson Rollins <jrollins@finestructure.net>
Subject: Re: `notmuch setup` replaces `~/.notmuch-config` instead of
	truncating	it
References: <AANLkTikKiKC716H+ddF0Q5T0xc=vGHHOVroLRwzO3ujV@mail.gmail.com>
	<87k4kdbd77.fsf@servo.finestructure.net>
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Cc: notmuch@notmuchmail.org
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On 11/16/2010 08:38 AM, Jameson Rollins wrote:
> On Tue, 16 Nov 2010 15:33:30 +0200, "Ciprian Dorin, Craciun" <ciprian.c=
raciun@gmail.com> wrote:
>>     So my question is: is this behaviour (of deleting the file and
>> creating a new one) deliberate? If not, could it be fixed (I could
>> provide a patch) to just update the file in place?
>=20
> Hi, Ciprian.  I had not noticed this, but now that you mention it, I se=
e
> that the same thing happened to me.  This behavior is surely not
> deliberate, and is definitely undesirable.  A patch would be welcome.

It often is desirable to do a replacement instead of truncation or
appending -- atomic replacement guarantees that a legitimate copy is
always available.  It eliminates a window of time when the config file
would be in an intermediate state.  Readers of the file always get
either the old state or the new state -- nothing in between.

However, you can address both concerns by detecting whether
~/.notmuch-config is a symlink and readlink()ing until you get to the
underlying file.  Then atomically replace the target instead of the
symlink itself.

	--dkg


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