easily open gem source directory in Textmate

mate-gem-source.bash

# change "bundler" to the name of any installed gem (run 'gem list' to see which gems are installed.)
# change "mate" to any prefered program that can open a directory. 'open' will open the file tree in Finder on OSX, for instance.

# the regex basically strips off the "/lib/<gem-name>.rb" from the "gem which" output.

gem which bundler | sed "s/\(.*\)\(.*\/.*\/.*\.rb\)$/\1/" | xargs mate

# alternate way
gem which bundler | ruby -e "puts gets.match(/(.*)\/lib\/.*/)[1]" | xargs mate