I have both OpenStudio versions 2.8.1 and 2.9.1 installed on my Mac with rbenv Ruby 2.2.4 and .bash_ profile setup as follow:
## add openstudio
export PATH="/Users/home/Desktop/App/Run/OpenStudio/OpenStudio_2_8_1/bin:$PATH"
export RUBYLIB="/Users/home/Desktop/App/Run/OpenStudio/OpenStudio_2_8_1/Ruby/"
wonder how to jump between 2 versions (2.8.1 and 2.9.1) for scripting works?