Shows a strategy for creating both MRI and JRuby versions of a gem.

build_gem.sh

# Builds the gem for the current rvm ruby/platform.
# Run this once for MRI and once for JRuby, as in:
#
# rvm 1.9
# ./build_gem.sh
# rvm jruby
# ./build_gem.sh


GEM_NAME=my_gem
GEM_SPEC=${GEM_NAME}.gemspec
RUBY_VERSION=`rvm current`
GEMFILE_LOCK_VERSION_SAVE_NAME=Gemfile.lock.${RUBY_VERSION}

echo Building gem $GEM_NAME from $GEM_SPEC for Ruby version $RUBY_VERSION.
echo The Gemfile.lock for this version will be copied to $GEMFILE_LOCK_VERSION_SAVE_NAME.

mv  Gemfile.lock  Gemfile.sav  2> /dev/null

echo Running bundle install...
bundle install
cp  Gemfile.lock $GEMFILE_LOCK_VERSION_SAVE_NAME

echo Building gem from $GEM_SPEC...
gem build $GEM_SPEC