PostgreSQL – query from bash script as database user ‘postgres’

Question

Try this one:

#!/bin/bash
psql -U postgres -d database_name -c "SELECT c_defaults  FROM user_info WHERE c_uid = 'testuser'"

Or using su:

#!/bin/bash
su -c "psql -d database_name -c \"SELECT c_defaults  FROM user_info WHERE c_uid = 'testuser'\"" postgres

And also sudo:

#!/bin/bash
sudo -u postgres -H -- psql -d database_name -c "SELECT c_defaults  FROM user_info WHERE c_uid = 'testuser'"