参考: http://guides.cocoapods.org/using/getting-started.html#installation
CocoaPods is built with Ruby and it will be installable with the default Ruby available on OS X. You can use a Ruby Version manager, however we recommend that you use the standard Ruby available on OS X unless you know what you're doing.
Using the default Ruby install will require you to use sudo when installing gems. (This is only an issue for the duration of the gem installation, though.)
$ sudo gem install cocoapods
If you encounter any problems during installation, please visit this guide.
<Sudo-less installation
If you do not want to grant RubyGems admin privileges for this process, you can tell RubyGems to install into your user directory by passing either the --user-install flag to gem install or by configuring the RubyGems environment. The latter is in our opinion the best solution. To do this, create or edit the .profile file in your home directory and add or amend it to include these lines:
export GEM_HOME=$HOME/.gem
export PATH=$GEM_HOME/bin:$PATH
Note that if you choose to use the --user-install option, you will still have to configure your .profile file to set the PATH or use the command prepended by the full path. You can find out where a gem is installed with gem which cocoapods. E.g.
$ gem install cocoapods --user-install 用sudo方式安装在Mac OSX 10.11上报错
$ gem which cocoapods
/Users/eloy/.gem/ruby/2.0.0/gems/cocoapods-0.29.0/lib/cocoapods.rb
$ /Users/eloy/.gem/ruby/2.0.0/bin/pod install
<Updating CocoaPods
To update CocoaPods you simply install the gem again
$ [sudo] gem install cocoapods
Or for a pre-release version
$ [sudo] gem install cocoapods --pre gem install cocoapods --user-install --pre
升级后在 Link Binary With Libraries 中libPods.a变为了libPods-TargetName.a，需要移除。