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Reply-To: <rol@as2917.net>
From: "Paul Rolland" <rol@as2917.net>
To: "'Patrick J. LoPresti'" <patl@users.sourceforge.net>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: clone() <-> getpid() bug in 2.6?
Date: Sun, 6 Jun 2004 19:31:16 +0200
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> > I though this was a job for mktemp and co.
> 
> Sure, if you want to create a unique filename on a local unshared
> disk.

Right.
 
> But suppose you want a unique filename on a partition which might be
> NFS-mounted with multiple concurrent writers.  Oh, and the year is
> 1997.  Still want to use mktemp?

Probably not...

> Bernstein decided to name each file:
> 
>     <time>.<PID>.<fully-qualified-domain-name>
> 
> This approach makes three assumptions.  First, that the time does not
> repeat.  Second, that the FQDN is unique.  Third, that the time
> changes (i.e., one second elapses) before a PID is reused on the local
> system.  Subject to these assumptions, this is a perfectly reliable,
> very efficient, lock-free way to create unique file names.
> 
> Can you do better?
Not sure it's the best place to run a contest...
However, I could have used something like :
<FQDN>.<time-up-to-usec>.<random-number>

But this is biased because I know I must find an answer with <PID> :-)

> Sure, Bernstein's code is an unmaintainable nightmare.  But his
> designs and implementations are usually pretty sound.  The last
> release of qmail was in 1998, and we still use it where I work.  Six
> years with zero crashes, zero dropped messages, and zero security
> holes is not a trivial track record for an MTA.

One point for him.

Paul


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