Gems, Eggs and Perl Modules

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

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

Starting with OS X Lion (10.7), 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. For example:

chmod +a 'user:<YOUR_NAME_HERE> allow add_subdirectory,add_file,delete_child,directory_inherit' /Library/Python/3.y/site-packages

will let you add packages to Python 3.y as yourself, which 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 the use of sudo.

Python packages (eggs) without sudo

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

With a brewed Python

Note, easy_install is deprecated. We install pip (or pip2 for Python 2) along with python/python2.

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 python@2 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 macOS, 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 and pip to install there, either use the --user switch or 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 rbenv or RVM then you should ignore this stuff

Brewed Ruby installs executables to $(brew --prefix)/opt/ruby/bin without sudo. You should add this to your path. See the caveats in the ruby formula for up-to-date information.

With system’s Ruby

To make Ruby install to /usr/local, 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 around 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 has 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 owned by 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 rbenv/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 this will install some other dependencies like Module::Install. Then put the appropriate incantation in your shell’s startup, e.g. 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 altogether for Perl

If you don’t even want (or can’t) use sudo for bootstrapping local::lib, just manually install local::lib in ~/perl5 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:

curl -L https://install.perlbrew.pl | bash
perlbrew install perl-5.16.2
echo ".~/perl5/perlbrew/etc/bashrc" >> ~/.bashrc