Redis and redis-rb example:

git clone git://github.com/ezmobius/redis-rb.git
cd redis-rb/
rake redis:install
rake dtach:install
rake redis:start &
rake install

cat <<EOF >>test.rb
require 'rubygems'
require 'redis'

r = Redis.new

r.delete('foo')

p'set foo to "bar"'
r['foo'] = 'bar'

p 'value of foo'
p r['foo']
EOF

ruby test.rb

If Redis is not started Ruby will exit at Redis.new for some reason without saying anything.

Use it at your own risk with e.g. Sinatra:

require 'redis'

module Cache
  mattr_accessor :redis
  class << self
    def get(key)
      Cache.redis.get(key)
    end

    def set(key, value, ttl=nil)
      if ttl
        Cache.redis.setex(key, ttl, value)
      else
        Cache.redis.set(key, value)
      end
    end

    def fetch(key)
      value = get(key)
      value = yield if block_given? && value.nil?
      value
    end

    def establish_connection
      redis_config = YAML.load_file(File.join(Dir.pwd, 'config', 'redis.yml'))
      Cache.redis.client.disconnect if Cache.redis
      Cache.redis = Redis.new(:host => redis_config["host"], :port => redis_config["port"])
    end
  end
end