Can you get DB username, pw, database name in Rails?

Question

From within rails you can create a configuration object and obtain the necessary information from it:

config   = Rails.configuration.database_configuration
host     = config[Rails.env]["host"]
database = config[Rails.env]["database"]
username = config[Rails.env]["username"]
password = config[Rails.env]["password"]

See the documentation for Rails::Configuration for details.

This just uses YAML::load to load the configuration from the database configuration file (database.yml) which you can use yourself to get the information from outside the rails environment:

require 'YAML'
info = YAML::load(IO.read("database.yml"))
print info["production"]["host"]
print info["production"]["database"]
...

Bryan's answer in the comment above deserves a little more exposure:

>> Rails.configuration.database_configuration[Rails.env]
=> {"encoding"=>"unicode", "username"=>"postgres", "adapter"=>"postgresql", "port"=>5432, "host"=>"localhost", "password"=>"postgres", "database"=>"mydb", "pool"=>5}

ActiveRecord::Base.connection_config

returns the connection configuration in a hash:

=> {:adapter=>ADAPTER_NAME, :host=>HOST, :port=>PORT, 
    :database=>DB, :pool=>POOL, :username=>USERNAME, 
    :password=>PASSWORD} 

---

As tpett remarked in their comment: this solution accounts for merging the configuration from database.yml and from the environment variable DATABASE_URL.

I think this is the simplest solution. After some testing (in Rails 5.2 at least) this will resolve DATABASE_URL correctly.

 ActiveRecord::Base.configurations[Rails.env]

As of Rails 6.1 ActiveRecord::Base.connection_config is deprecated. The new proper way to do this is via ActiveRecord::Base.connection_db_config

ActiveRecord::Base.connection_config => #<ActiveRecord::DatabaseConfigurations::HashConfig @env_name="development", @name="primary", @configuration_hash={:adapter=>"mysql2", :encoding=>"utf8mb4", :database=>"your-db-name", :pool=>5, :host=>"127.0.0.1", :username=>"root", :password=>nil, :socket=>"/var/run/mysqld/mysqld.sock"}>

And you will get a ActiveRecord::DatabaseConfigurations::HashConfig object back.

Old question but this was one of my first stops in looking up how to do this so I figure this may help someone else. I normally have .my.cnf files in the home directory. So using the 'parseconfig' gem and some ERB syntax in my database.yml config file means I've got dynamic file that I can feel good about checking into source control and also simplify deployments (in my case). Also note the list of common sockets, this makes it easier to move my app to different operating systems that might have a different Unix socket path.

<% 
    require 'parseconfig'
    c=ParseConfig.new('../../.my.cnf') %>

mysqlevn: &mysql
  adapter: mysql 
  username: <%= c.params['client']['user'] %>
  password: <%= c.params['client']['password'] %>
  host: localhost 
  socket: <%= [ 
  '/var/run/mysqld/mysqld.sock',
  '/var/lib/mysql/mysql.sock',
  '/tmp/mysqld.sock',
  '/tmp/mysql.sock'].detect { |socket| File.exist?(socket) } %>

production:
  database: app_production
  <<: *mysql


development:
  database: app_development 
  <<: *mysql

# Do not set this db to the same as development or production.
test:
  database: app_test
  <<: *mysql

ref: http://effectif.com/articles/database-yml-should-be-checked-in