brew/docs/Gems,-Eggs-and-Perl-Modules.md
Mike McQuaid f76ffa2eaa
docs: tweak wording/formatting.
Co-authored-by: Eric Knibbe <enk3@outlook.com>
2021-07-14 14:22:31 +01:00

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# 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`
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:
```sh
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 isnt a
writable location. But if you installed Homebrew as we recommend on macOS Intel,
`/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 using systems 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](https://docs.python.org/2/install/index.html#inst-alt-install-user).
That dir might not yet exist, but you can create it:
```sh
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/$py_version_short/lib/python/site-packages
```
### Using virtualenv (with system Python)
[Virtualenv](https://virtualenv.pypa.io/) ships `pip` and
creates isolated Python environments with separate site-packages,
therefore you wont need sudo.
## Rubygems without sudo
**If you use rbenv or RVM then you should ignore this stuff**
Brewed Ruby installs executables to `$(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 systems Ruby
To make Ruby install to `/usr/local`, we need to add
`gem: -n/usr/local/bin` to your `~/.gemrc`. Its YAML, so do it manually
or use this:
```sh
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:
```sh
sudo gem update --system
```
### An alternative
Just install everything into the Homebrew prefix like this:
```sh
echo "export GEM_HOME=\"$(brew --prefix)\"" >> ~/.bashrc
```
### It doesnt work! I get some “permissions” error when I try to install stuff!
*Note, maybe you shouldnt 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:
```sh
sudo chown -R $(whoami) /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`](https://metacpan.org/pod/local::lib) with sudo:
```sh
sudo cpan local::lib
```
Note that this will install some other dependencies like `Module::Install`.
Then put the appropriate incantation in your shells startup, e.g. for
`.profile` you insert the below, for others see the
[`local::lib`](https://metacpan.org/pod/local::lib) docs.
```sh
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 dont even want (or cant) 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:
```sh
curl -L https://install.perlbrew.pl | bash
perlbrew install perl-5.16.2
echo ".~/perl5/perlbrew/etc/bashrc" >> ~/.bashrc
```