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help / color / mirror / Atom feedFrom: Ken Dibble <[email protected]>
To: [email protected]
Subject: Re: Command Line option misunderstanding
Date: Mon, 2 Dec 2024 16:32:13 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
<CAKFQuwaNdRVNgKi014CGykDin43gsaSDgX+TKucbNsa-ZD1aEw@mail.gmail.com>
<[email protected]>
On 12/2/24 15:36, David G. Johnston wrote:
> On Mon, Dec 2, 2024 at 11:47 AM wrote: ----attempt 1-- psql -h anna -d
> GT7 -v v1=12 -c 'select :v1'ERROR: syntax error at or near ":" LINE 1:
> select :v1 The variable got
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> On Mon, Dec 2, 2024 at 11:47 AM <[email protected]> wrote:
>
>
> ----attempt 1--
> psql -h anna -d GT7 -v v1=12 -c 'select :v1'
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> The variable got assigned correctly but it isn't in scope here due to
> the how -c is implemented, as the others noted.
>
> ----end attempt---
>
> ---attempt 2 ---
> psql -h anna -d GT7 -vv1=1 -c 'select ":v1" '
> ERROR: column ":v1" does not exist
> LINE 1: select ":v1"
>
> You double-quoted the whole thing so it's taken as a column name. Has
> no relevance to the problem at hand.
>
> ---end attempt ---
>
> --- atttempt 3----
> psql -h anna -d GT7 -vv1=1 -c 'select :v1'
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> Redundant with 1
>
> ---end attempt
>
> ---attempt 4----
> sql -h anna -d GT7 -v "v1=1" -c "select :v1"
> ERROR: syntax error at or near ":"
> LINE 1: select ":v1"
>
> Redundant with 1 and 3, putting quotes around the shell option value
> only makes explicit what is implicit/optional. This is also a shell
> usage education issue, not psql specific.
>
> --- end attempt---
>
> ---attempt 5 ---
> psql -h anna -d GT7 -v 'v1=1' -c 'select ":v1" '
> ERROR: column ":v1" does not exist
> LINE 1: select ":v1"
>
> Redundant with 2
>
> ----end attempt
>
> --- attempt 6---
> psql -h anna -d GT7 -v :v1=1 -c 'select ":v1" '
> psql: error: invalid variable name: ":v1"
>
> Shell command failed since you cannot name a variable with a leading
> colon, otherwise the chosen syntax for referencing a variable would be
> challenging
>
> ---end attempt
>
> --- attempt 7 ---
> psql -h anna -d GT7 -v "v1"=1 -c 'select ":v1" '
> ERROR: column ":v1" does not exist
> LINE 1: select ":v1"
>
> Another redundant attempt using double-quotes
>
> --- end attempt
>
> ---attempt 8 ---
> psql -h anna -d GT7 -v 'v1'=1 -c 'select ":v1" '
> ERROR: column ":v1" does not exist
> LINE 1: select ":v1"
>
> And again...
>
> --- end attempt ---
>
> ---attempt 9 ---
> psql -h anna -d GT7 -c '\set v1 12; select ":v1" '
>
> ... Not realizing how -c and meta-commands interplay (or don't in this
> case) really led you to try lots of stuff that cannot work but is
> unrelated to setting a variable.
>
> --- end attempt ----
>
>
> Skipping 10-17 as redundant variations on not reading how -c works.
>
>
>
> ---attempt 18---
> psql -h anna -d GT7 -v --set v1=12 -c 'select :v1 '
> Password for user v1=12:
>
> You can get odd errors when you don't following the syntax diagrams
> and shell command writing rules...
>
> ---end attempt---
>
>
> ---attempt 19 ---
> kdibble@thinkstation:~/development/gt7-scraper$ psql -h anna -d GT7
> --set v1=12 -c 'select :v1 '
>
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> Back to redundant with 1...
>
> ---end attempt
>
> --- attempt 20---
> psql -h anna -d GT7 -v --set v1=12 -c 'select :v1 '
> Password for user v1=12:
>
> Again, not following syntax rules.
>
> --end attempt---
>
> ---attempt 21 ---
> psql -h anna -d GT7 -v v1 --set v1=12 -c 'select :v1 '
>
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> And back to redundant with 1 after figuring out syntax rules for -v/--set
>
> ---end attempt
>
> ---attempt 22 ---
> psql -h anna -d GT7 -v v1 --set =12 -c 'select :v1 '
> psql: error: invalid variable name: ""
>
> And now invalid shell syntax form for the set command.
>
> ---end attempt---
>
> ---attempt 23---
> psql -h anna -d GT7 -v v1 --set 12 -c 'select :v1 '
>
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> Redundant with 1 again...
>
> ---end attempt
>
> ---attempt 24 ---
> psql -h anna -d GT7 -v v1 --set v1=12 -c 'select :v1 '
>
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> And again...
>
> ---end attempt---
>
> ---attempt 25---
> psql -h anna -d GT7 -v --set v1=12 -c 'select :v1 '
> Password for user v1=12:
>
> Random stuff when inventing syntax again
>
> ----
>
> ---attempt 26 ---
> psql -h anna -d GT7 --set v1=12 -c 'select :v1 '
>
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> Redundant with 1 again...
>
> ---end attempt
>
> ---attempt 27---
> psql -h anna -d GT7 -v v1="3" -c "select :v1"
> + psql -h anna -d GT7 -v v1=3 -c 'select :v1'
>
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> Redundant with 1 again...
>
> ---end attempt
>
> ---attempt 28---
> psql -h anna -d GT7 -v v1='3' -c "select :v1"
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> Redundant with again
>
> --- end attempt ---
>
> ---attempt 29---
> psql -h anna -d GT7 -c '\set v1 12; select :v1 '
>
> Didn't read how -c works
>
> ---end attempt ---
>
> ---attempt 30 ---
> psql -h anna -d GT7 -v --set v1:=12 -c 'select :v1 '
> Password for user v1:=12:
>
> Don't understand shell syntax for -v versus --set (repeat)
>
> ---end attempt ---
>
> ---attempt 31 ---
> psql -h anna -d GT7 --variable=v1=12 -c 'select :v1 '
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> Redundant with 1 again
>
> ---end attempt---
>
> ---attempt 32---
> psql -h anna -d GT7 --variable="v1=12" -c 'select :v1 '
> ERROR: syntax error at or near ":"
> LINE 1: select :v1
>
> Redundant with 1 again.
>
> ---end attempt---
>
>
> If short, you figured out a bunch of ways to write valid and invalid
> variable specifications. The invalid ones give you various different
> errors. The correct ones all give you the same error since you cannot
> use a variable along with -c, which is documented in -c, not
> variables, since they get set just fine.
> David J.
As I stated, I was trying to figure out if there was a problem with the
documentation. Below is the documentation for -c and I cannot find
anywhere it says you cannot use variables with it. The only way that
that could make sense is if declaring a variable is a psql specific
feature and -v is hiding behind that in the man page. I could find no
place where it is documented that declaring a variable is a psql
specific feature. In addition, of what use would it be to declare a
variable that could not be accessed without a command. It wouldn't make
sense (at least to me) to declare something that is going immediately
out of scope before the next command executes or when the psql command
(and hence the session) ends.
In addition, declarations seems to work fine, it is assigning that fails.
If the variable did not exist or were out of scope it should generate an
error, which it does not.
$ psql -h anna -d GT7 -c '\set v1 12; select :v1 '
autocommit on
$
Variable does not exist here.
$psql -h anna -d GT7 -c 'select :v1 '
autocommit on
ERROR: syntax error at or near ":"
LINE 1: select :v1
$
One would hope that if the variable were out of scope it would generate
an error.
Is there any explanation for this?
--man page extract --
-c command
--command=command
Specifies that psql is to execute the given command string,
command. This option can be repeated and combined in any
order with
the -f option. When either -c or -f is specified, psql does not
read commands from standard input; instead it terminates after
processing all the -c and -f options in sequence.
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. Thus you cannot mix SQL and psql
meta-commands within a -c option. To achieve that, you could use
repeated -c options or pipe the string into psql, for example:
psql -c '\x' -c 'SELECT * FROM foo;'
or
echo '\x \\ SELECT * FROM foo;' | psql
(\\ is the separator meta-command.)
Each SQL command string passed to -c is sent to the server as a
single request. Because of this, the server executes it as a
single
transaction even if the string contains multiple SQL commands,
unless there are explicit BEGIN/COMMIT commands included in the
string to divide it into multiple transactions. (See
Section 55.2.2.1 for more details about how the server handles
multi-query strings.)
If having several commands executed in one transaction is not
desired, use repeated -c commands or feed multiple commands to
psql's standard input, either using echo as illustrated
above, or
via a shell here-document, for example:
psql <<EOF
\x
SELECT * FROM foo;
EOF
---end of extract---
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