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To: John Rouillard <rouilj@renesys.com>, Tim <elatllat@gmail.com>,
	pgsql-admin@postgresql.org
Subject: Re: archive_command vs. cp -i 
In-reply-to: <20654.1308333896@sss.pgh.pa.us> 
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Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Fri, 17 Jun 2011 14:04:56 -0400"
Date: Fri, 17 Jun 2011 19:17:56 -0400
Message-ID: <563.1308352676@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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I wrote:
> John Rouillard <rouilj@renesys.com> writes:
>> I get the same result (0 exit status) on solaris 8 and solaris 10 with
>> /bin/cp.  I wonder what platform the example worked on.

> cp does behave as the example suggests for me, on OS X and HPUX.  I
> suspect Bruce tested it on some BSD variant before putting it in the
> docs.  That would suggest that it probably works that way on most (all?)
> BSDen.  Still, if the GNU version doesn't act that way, we have a
> problem.

> The test-and-cp approach seems the most likely to be portable.

I've applied patches for this.  It turns out that before 9.0, we did
have a warning that cp -i wasn't very trustworthy:

    It is advisable to test your proposed archive command to ensure that it
    indeed does not overwrite an existing file, <emphasis>and that it returns
    nonzero status in this case</>.  We have found that <literal>cp -i</> does
    this correctly on some platforms but not others.  If the chosen command

but somebody "improved" that text in a way that made it sound like you
could expect the command to work most places.  On the whole it seems
like a better idea to provide a sample command that is safe most
everywhere, and then mention cp -i as a nonportable simplification.

			regards, tom lane