Installing Ruby gems not working with Home Brew - ruby

Question

The gems I install via sudo gem install ... can't be executed (I get a command not found).
They seem to install into /usr/local/Cellar/ which is Brew's install directory (also, the gems in /Library/Ruby/ don't work either). Is there anything else I need to do to make the gems executable? I'm using ZSH on Mac OS X 10.6 with Ruby v1.8 for the one in Brew.
EDIT: It seems to be working now. I just went out for a few hours and came back to try it again.

Answer 1

Homebrew is nice. However unlike brew and npm, gem does not make aliases in /usr/local/bin automatically.
Solution
I went for a very simple approach (as of March 2020):
# Based on "`brew --prefix ruby`/bin"
export PATH=/usr/local/opt/ruby/bin:$PATH
# Based on "`gem environment gemdir`/bin"
export PATH=/usr/local/lib/ruby/gems/3.0.0/bin:$PATH
Add this to your .bashrc (or .bash_profile, .zshrc, etc.).
That's it! Now all Ruby bins and installed gems will be available from your shell!
In older versions of Homebrew (before 2017), there was a separate package for Ruby 2 called ruby20, for which you'd use the following snippet instead:
export PATH=/usr/local/opt/ruby20/bin:$PATH
This line was the only line needed at the time. But, in Ruby 2.1 the gems got moved to a separate directory. No longer under /usr/local/opt/ruby/bin, but instead at /usr/local/lib/ruby/gems/2.0.0/bin (where "2.0.0" is the last major Ruby version for Gem's purposes).
How it works
Homebrew keeps track of where it installed a package, and maintains a symbolic link for you that points there.
$ brew --prefix ruby
/usr/local/opt/ruby
$ l /usr/local/opt/ruby
/usr/local/opt/ruby# -> ../Cellar/ruby/2.5.3_1
Effectively, adding /usr/local/opt/ruby to PATH is the same as the following:
export PATH=/usr/local/Cellar/ruby/2.5.3_1/bin:$PATH
Except, this long version hardcodes the currently installed version of Ruby and would stop working next time you upgrade Ruby.
As for Gem, the following command will tell you the exact directory Gem adds new packages to:
$ gem environment gemdir
/usr/local/lib/ruby/gems/2.7.0
Tools
These tools were meant to automatically bridge between Homebrew and Gem:
josh/brew-gem (no longer exists)
indirect/brewbygems (unmaintained)
I haven't used these but they might work for you.

Answer 2

brew unlink ruby; brew link ruby might add symlinks to /usr/local/bin/:
$ which sass
$ brew unlink ruby; brew link ruby
Unlinking /usr/local/Cellar/ruby/2.0.0-p0... 20 links removed
Linking /usr/local/Cellar/ruby/2.0.0-p0... 31 symlinks created
$ which sass
/usr/local/bin/sass
brew --prefix ruby is still pretty slow, but you could also just add /usr/local/opt/ruby/bin to the path.
$ time brew --prefix ruby
/usr/local/opt/ruby
0.216
$ time brew --prefix ruby
/usr/local/opt/ruby
0.076
$ stat -f%Y /usr/local/opt/ruby
../Cellar/ruby/2.0.0-p0

Answer 3

I like home brew. There's probably a better way to do this, but if you run:
gem environment
That will print out a nice list of all the relevant paths. Look for the one labeled EXECUTABLE DIRECTORY. That's the one you want to add to your path. In my case that's /usr/local/Cellar/ruby/1.9.3-p362/bin/ruby but I would imagine it would change with newer version of Ruby.
I'm using /bin/bash as my shell, but the process of adding it to your path should be pretty much the name.
I use TextWrangler (via the command line tools) to edit my .profile file. To do that, it's just:
edit ~/.profile
When your done, either close your terminal and open a new one, or run:
source ~/.profile

Answer 4

Using the info in Timo's answer, I've got this:
PATH=/usr/local/opt/ruby/bin:$PATH
GEMSDIR=$(gem environment gemdir)/bin
PATH=$GEMSDIR:$PATH
export PATH
Works for Homebrew, works for the separate gems directory, and doesn't hardcode a Ruby version.

Answer 5

You can be fine with ruby installed by homebrew too.. You just lack the functionality of custom gemsets with homebrew.
first do:
sudo nano /etc/paths
this will bring up nano editor,
then add the following to the paths:
/usr/local/Cellar/ruby/1.9.3-p194/bin
your version of ruby will probably vary.
Thats it. It should now detect your gems.
Oh, btw, you need to Ctrl+X > y > ENTER to save a file in nano.

Answer 6

Instead of using => $(cd $(which gem)/..; pwd)
You could use this instead => $(brew --prefix ruby)/bin

Answer 7

I think this evolve a bit.
Just add
export PATH=/usr/local/opt/ruby/bin:$PATH
To your .bashrc (or .bash_profile, .zshrc/.bashrc, .. – whatever you use).
If you have a problem with ruby itself
brew unlink ruby
brew link ruby