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From: Ken Dibble <[email protected]>
To: [email protected]
Subject: Re: Command Line option misunderstanding
Date: Tue, 3 Dec 2024 03:56:22 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
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On 12/2/24 19:11, David G. Johnston wrote:
> On Mon, Dec 2, 2024 at 4:50 PM wrote: The problem seems to be, as 
> alluded to by others attempting to help me that the problem only 
> exists when using -c on the same line a
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> On Mon, Dec 2, 2024 at 4:50 PM <[email protected]> wrote:
>
>     The problem seems to be, as alluded to by others attempting to help me
>
>     that the problem only exists when using -c on the same line as -v.
>
> The word "line" here belies further misunderstanding of how 
> shell-executed commands work (the following "two line" command is 
> still just one actual multiple-option command invocation).
> psql -v a=1 \
> -c 'select :a'
>
> It is best to just say "using -c and -v together".
>
> It is correct that we haven't pointed out, probably because for 
> experienced people it seems obvious, that using -v and -c (or putting 
> \set in -c) is a pointless thing to do.  But psql doesn't go about 
> trying to analyze intent here so, yes, you either get useless 
> successful output in response or a confused server.
>
> That said...
> psql -v a=1 -c '\echo :a' postgres
> 1
>
> So it truly is just this specific SQL-related usage that is pointless, 
> not combining -v and -c generally (I'm sure a useful backslash command 
> can be substituted for \echo)
>
>
>     Related Question:
>
>     Documentation says:
>
>     /|command|/ must be either a command string that is completely
>     parsable by the server (i.e., it contains no psql-specific
>     features), or a single backslash command.
>
>     $psql -h anna -d GT7   -c "\set  a '11117' \\ select evt_id from
>     events where sport_mode_evt_id=:a"
>
> Really not caring that you are turning on autocommit...
>
> Anyway, what I believe you managed to accomplish here is to set the 
> named variable "a" to the value <single-quote 11117 single-quote 
> blah-blah-blah equals colon a>
>
> Then proceeded to do nothing with that variable since the -c command 
> was done being evaluated in the "single backslash command" mode.
>
> David J.
>
Thanks for your time and explanations.

Ken

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