这个是 db 的配置文件

default: &default
  adapter: mysql2
  encoding: utf8
  host: localhost
  database: test_db
  username: root
  password: root
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

development:
  <<: *default

test:
  <<: *default

production:
  <<: *default
  host: <%= ENV['DATABASE_HOST'] %>
  username: <%= ENV['DATABASE_USERNAME'] %>
  password: <%= ENV['DATABASE_PASSWORD'] %>

这个是我 ~/.zshrc 的配置

export DATABASE_HOST=0.0.0.0
export DATABASE_USERNAME=hahaha
export DATABASE_PASSWORD=fuckfuck

然后 RAILS_ENV=production rails c

> ActiveRecord::Base.configurations
    {
        "default"     => {
            "adapter"  => "mysql2",
            "encoding" => "utf8",
            "host"     => "localhost",
            "database" => "test_db",
            "username" => "root",
            "password" => "root",
            "pool"     => 5
        },
        "development" => {
            "adapter"  => "mysql2",
            "encoding" => "utf8",
            "host"     => "localhost",
            "database" => "test_db",
            "username" => "root",
            "password" => "root",
            "pool"     => 5
        },
        "test"        => {
            "adapter"  => "mysql2",
            "encoding" => "utf8",
            "host"     => "localhost",
            "database" => "test_db",
            "username" => "root",
            "password" => "root",
            "pool"     => 5
        },
        "production"  => {
            "adapter"  => "mysql2",
            "encoding" => "utf8",
            "host"     => nil,
            "database" => "test_db",
            "username" => nil,
            "password" => nil,
            "pool"     => 5
        }
    }

我的 .zshrc 中明明是有配置环境变量的，也执行过 source ~/.zshrc 了可是就是读不到啊。 另外 如果使用 RAILS_ENV=production DATABASE_HOST=xxxx rails c 的方式去启动是可以读到的。这个问题在 mac 和 ubuntu 上都存在。