How can I print text to stdout from a psql query? - postgresql

Question

I have the following (massaged) psql script invoked from a bash shell:
foo=$( psql -q -t -R $'\x01' -F $'\x02' \
--variable="title=something" \
--variable="severity=level9" \
--pset='format=unaligned' \
<<'EOF'
SET standard_conforming_strings=on;
SET myvars.title = :title;
SET myvars.severity = :severity;
DO $$
BEGIN
IF EXISTS ( SELECT 1 from my_database
WHERE title=current_setting('myvars.title') \
AND severity=current_setting('myvars.severity') )
THEN
RAISE NOTICE 'Found existing entry';
ELSE
RAISE NOTICE 'Did not find existing entry';
END IF;
END;
$$;
EOF
)
I was hoping to capture in the bash variable "foo" some indication of whether or not the query succeeded. I thought I could add some kind of print/echo/return/whatever statement after each of the RAISE NOTICE statements to output 0 or 1 from the psql statement so it could be captured in foo for later evaluation in the bash script, e.g.:
foo=$( psql -q -t -R $'\x01' -F $'\x02' \
--variable="title=something" \
--variable="severity=level9" \
--pset='format=unaligned' \
<<'EOF'
SET standard_conforming_strings=on;
SET myvars.title = :title;
SET myvars.severity = :severity;
DO $$
BEGIN
IF EXISTS ( SELECT 1 from my_database
WHERE title=current_setting('myvars.title') \
AND severity=current_setting('myvars.severity') )
THEN
RAISE NOTICE 'Found existing entry';
magical_incantation 1;
ELSE
RAISE NOTICE 'Did not find existing entry';
magical_incantation 0;
END IF;
END;
$$;
EOF
)
I've been reading psql documentation for about the past 5 hours and cannot figure out the command/syntax of my imaginary magical_incantation above.
I am new to psql and tweaking someone else's code. I cannot change the main structure of the script, I just need some way to print a value.
Can anyone point me in the right direction?

Answer 1

\echo prints to stdout in psql. I think RAISE NOTICE goes to stderr.
It is possible to select into a psql variable and then echo it. A basic run-down is at How do you use script variables in PostgreSQL?
However I am not sure of any way to pull a query result into a variable at present.
Assuming that is not the answer you are looking for is just a SELECT.
So something like:
SELECT (EXISTS (....))::int;
-- true is 1, false is 0
Note there is no way to do this from a DO statement so you would have to actually create a function if you need to do this from plpgsql.