The Problem

When install gem in Mac OS X Yosemite, I got the following error:

ERROR: While executing gem … (Gem::FilePermissionError) You don’t have write permissions for the /Library/Ruby/Gems/2.0.0 directory.

The Solution

Step 1: Install Rbenv

brew install rbenv ruby-build

echo ‘export PATH=”$HOME/.rbenv/bin:$PATH”’ » ~/.zshrc

echo ‘eval “$(rbenv init -)”’ » ~/.zshrc

Note: Modify your ~/.bash_profile instead of ~/.zshrc file if you’re not using zsh.

Step 2: Close your terminal and restart the shell

Step 3: Install Ruby, Set globle and Rehash

rbenv install 2.0.0-p247

rbenv global 2.0.0-p247

rbenv rehash

Step 4: gem install as usual

Now you should get the gem successfully installed!