Gems, Eggs and Perl Modules

On a fresh OS X installation there are three empty directories:

/Library/Ruby
/Library/Python
/Library/Perl

When you gem install, cpan -i or easy_install stuff gets installed to these directories in a nicely segregated fashion similar to Homebrew.

These directories start empty — you are meant to fill them with your stuff and not worry about it.

On fresh OS X installing to these three directories doesn’t require sudo.

So why was I using sudo?

Habit maybe?

One reason is executables go in /usr/local/bin. Usually this isn’t a writable location. But if you installed Homebrew as we recommend, /usr/local will be writable without sudo. So now you are good to install the development tools you need without risking a sudo.

Rubygems without sudo

If you use RVM then you should ignore this stuff.

Ruby installs executables to ~/.gem/bin without sudo. This is non-ideal, so this section is about making it install to /usr/local instead.

We need to add gem: -n/usr/local/bin to your ~/.gemrc. It’s YAML so do it manually or use this:

ruby -C$HOME -ryaml -e "
gemrc = YAML::load_file('.gemrc') rescue {}
gemrc['gem'] = '-n/usr/local/bin'
YAML::dump(gemrc, File.new('.gemrc', 'w'))"

However all versions of RubyGems before 1.3.6 are buggy and ignore the above setting. Sadly a fresh install of Snow Leopard comes with 1.3.5. Currently the only known way to get round this is to upgrade rubygems as root:

sudo gem update --system

An Alternative

Just install everything into the Homebrew prefix like this:

echo "export GEM_HOME='$(brew --prefix)'" >> ~/.bashrc

It doesn’t work! I get some “permissions” error when I try to install stuff!

If you ever did a sudo gem, etc. before then a lot of files will have been created chown root. Fix with:

sudo chown -R $USER /Library/Ruby /Library/Perl /Library/Python