Gems, Eggs and Perl Modules

On a fresh OS X installation there are three empty directories for add-ons available to all users:

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

Since OS X Lion, you need sudo to install to these like so: sudo gem install, sudo easy_install or sudo cpan -i.

An option to avoid sudo is to use an access control list: chmod +a 'user:YOUR_NAME_HERE allow add_subdirectory,add_file,delete_child,directory_inherit' /Library/Python/2.7/site-packages, for example, will let you add packages to Python 2.7 as yourself. That is probably safer than changing the group ownership of the directory.

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.

Python packages (eggs) without sudo

Rather than changing the rights on /Library/Python, we recommend the following options:

With a brewed Python – you don’t need sudo

Note, easy_install is deprecated. We install pip (or pip3 for python3) along with python/3.

We set up distutils such that pip install will always put modules in $(brew --prefix)/lib/pythonX.Y/site-packages and scripts in $(brew --prefix)/share/python. Therefore, you won’t need sudo.

Do brew info python or brew info python3 for precise information about the paths. Note, a brewed Python still searches for modules in /Library/Python/X.Y/site-packages and also in ~/Library/Python/X.Y/lib/python/site-packages.

With system’s Python

This is only recommended if you don’t use a brewed Python.

On OS X, any Python version X.Y also searches in ~/Library/Python/X.Y/lib/python/site-packages for modules. That dir might not yet exist, but you can create it: mkdir -p ~/Library/Python/2.7/lib/python/site-packages

To teach easy_install to install there, "create a ~/.pydistutils.cfg file with the following content:

[install]
install_lib = ~/Library/Python/$py_version_short/lib/python/site-packages

Using virtualenv – works with brewed and system’s Python

Virtualenv ships pip and creates isolated Python environments with separate site-packages, therefore you won’t need 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:

echo "gem: -n/usr/local/bin" >> ~/.gemrc

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!

Note, maybe you shouldn’t do this on Lion, since Apple have decided it is not a good default.

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

Perl CPAN Modules without sudo

The Perl module local::lib works similarly to rvm (although for modules only, not perl installations). A simple solution that only pollutes your /Library/Perl a little is to install local::lib with sudo:

sudo cpan local::lib

Note that will install some other dependencies like Module::Install. Then put the appropriate incantation in your shell’s startup, eg. for .bash_profile you insert the below, for others see the local::lib docs.

eval $(perl -I$HOME/perl5/lib/perl5 -Mlocal::lib)

Now (after you restart your shell) cpan or perl -MCPAN -eshell etc. will install modules and binaries in ~/perl5 and the relevant subdirectories will be in your PATH and PERL5LIB etc.

Avoiding sudo alltogether for Perl

If you don’t even want (or can’t) use sudo for bootstrapping local::lib just manually install local::lib in ~/perl5 (or wherever you want) and add the relevant path to PERL5LIB before the .bashrc eval incantation.

Another alternative is to use perlbrew to install a separate copy of Perl in your home directory, or wherever you like.