List all gems without version numbers, and easily re-install them

Sometimes when upgrading ruby versions or moving from one dev machine to another I want a list of all my gems that I can then later give to gem install. This sed command strips out the version numbers that usually get appended to gem list

gem list | sed 's/(.*)//'

or

gem list | sed 's/(.*)//' > gemlist.txt

Then, when you want to re-install the gems you can:

cat gemlist.txt | xargs gem install