Determine if a user and database are available

Hi Everyone,

I have another beginner question. I am trying to use pg_isready to
determine if a database and user are present. The program seems to
always succeed, even when I delete the user or the database.

This baffles me from the man page. I guess this explains the behavior
I am seeing.

NOTES
It is not necessary to supply correct user name, password, or database
name values to obtain the server status; however, if incorrect values
are provided, the server will log a failed connection attempt.

A typical usage is shown below, where variables are parsed from a config file.

password=$(grep 'DD_DB_Rpass' dojoConfig.yml | awk '{ print $2 }')
hostname=$(grep 'DD_DB_Host' dojoConfig.yml | awk '{ print $2 }')
database=$(grep 'DD_DB_Name' dojoConfig.yml | awk '{ print $2 }')
username=$(grep 'DD_DB_Ruser' dojoConfig.yml | awk '{ print $2 }')

PGPASSWORD=${password} pg_isready \
-h "${hostname}" -U "${username}" -d "${database}"

Given the NOTES in the man page, how do we determine if a user and
database are present using the shell? Is there another utility we
should be using?

Thanks in advance,

Jeff