A shell script to calculate the days between 2 dates with postgres

days.sh

#!/bin/sh

echo "Use the following format: yyyy-mm-dd (ex: 2022-01-15)"
echo "First day: "
read FIRST_DAY

echo "Last day: "
read LAST_DAY


psql <<EOF
with sorted as (
     select
	least ('${FIRST_DAY}'::date, '${LAST_DAY}'::date) as first_day,
	greatest ('${FIRST_DAY}'::date, '${LAST_DAY}'::date) as last_day
)
select
     generate_series(sorted.first_day, last_day, '1 day'::interval)::date as days
     from sorted;
EOF