How do I run a Ruby Gem?

It seems that Debian/Ubuntu drops ruby gems into /var/lib/gems/1.8/bin.

So the solution (at least for Ubuntu/Debian) is:

$ sudo -s
# echo 'PATH=/var/lib/gems/1.8/bin:$PATH' > /etc/profile.d/gemspath.sh
# chmod 0755 /etc/profile.d/gemspath.sh

...and then open a new shell session.

(This is fixed in Ubuntu 11.10.)

If you happen to have installed Ruby through rbenv, you'll need to execute the following command

rbenv rehash

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