use RVM

RVM is used to manage ruby version.

installation

curl -L https://get.rvm.io | bash -s stable --autolibs=enabled

then restart your terminal to eunsure rvm is loaded

install ruby by rvm

rvm install ruby-1.9.3-p125

rvm install 1.9.3

rvm use 1.9.3 to use the installed ruby

rvm 1.9.3 --default to set to default ruby version

rvm gemset

create a new gemset for app

rvm gemset create <name>

use a gemset

rvm gemset use <name>

shorthand

rvm 1.9.3@<name> --create

.rvmrc file

1. one gemset per project
2. automatically switch between ruby versions

create a project .rvmrc file

cd myapp
rvm 1.9.3@myapp --create --rvmrc