Re: Syntax error when combining --set and --command has me stumped

On 7/28/22 12:40, Ron wrote:
>
> $ alias psql12
> alias psql12='/usr/lib/postgresql/12/bin/psql -p5433'
>
> This works ask expected:
>
> $ psql12 --set num=42 -ac "\echo :num"
> echo :num
> 42
>
> And so does this:
>
> $ psql12 --set num=42
> psql (12.11 (Ubuntu 12.11-1.pgdg18.04+1))
> Type "help" for help.
>
> postgres=# select :num;
>  ?column?
> ----------
>        42
> (1 row)
>
>
> But trying to use a variable (both with and without single quotes) in a
> --command statement other than "\echo" throws a syntax error at the colon:
>
> $ psql12 --set num=42 -ac "select :num;"
> select :num;
> ERROR:  syntax error at or near ":"
> LINE 1: select :num;
>                ^
> $ psql12 --set num=42 -ac "select :'num';"
> select :'num';
> ERROR:  syntax error at or near ":"
> LINE 1: select :'num';
>                ^
>
> What secret sauce am I missing to get this to work?

From here:

https://www.postgresql.org/docs/current/app-psql.html

-c command

...

Because of this behavior, putting more than one SQL command in a single
-c string often has unexpected results. It's better to 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

So:

echo '\set num 42 \\ SELECT :num;' | psql -d test -U aklaver
Null display is "NULL".
?column?
----------
42

or:

psql -d test -U aklaver <<EOF
> \set num 42
> SELECT :num;
> EOF
Null display is "NULL".
?column?
----------
42
(1 row)

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com