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 your operating system’s health.

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