我的解决方案。

摘要 OS X 10.11 EI Capitan 安装Cocoapods 常规报错问题
OS X 10.11 EI Capitan 安装Cocoapods，报错， WTF！使用以下命令一句话解决:

sudo gem install -n /usr/local/bin cocoapods

更新Gem

sudo gem update --system -n /usr/local/bin

如果作者的方法没有帮你解决问题，请向下看。

网上的方案

OS X 10.11 安装Cocoapods 出现问题的解决方法
今天尝试用 Cocoapods安装个第三方库.. 输入pod install， 发现 command not find。

估计是升级10.11后Cocoapods被干掉了。

我输入

sudo gem install cocoa pods

之后，出现如下问题

ERROR:  While executing gem ... (Gem::DependencyError)
Unable to resolve dependencies: cocoapods requires cocoapods-core (= 0.33.1), claide (~> 0.6.1), cocoapods-downloader (~> 0.6.1), cocoapods-plugins (~> 0.2.0), cocoapods-try (~> 0.3.0), cocoapods-trunk (~> 0.1.1), nap (~> 0.7)

解决方法：

sudo gem update --system

在Stackoverflow上找到了解决方法：

在终端中输入：

sudo nvram boot-args="rootless=0"; sudo reboot

然后你的电脑会重启，之后再输入

 sudo gem install cocoapods -V

就可以了

不放心的话输入

pod --version
0.37.2

显示出版本就说明成功了

但是之后我pod install的时候又花式出错

[!] Unable to add a source with url `https://github.com/CocoaPods/Specs.git` named `master`.
You can try adding it manually in `~/.cocoapods/repos` or via `pod repo add`.

我尝试按提示的方法

pod repo add master https://github.com/CocoaPods/Specs.git

然而还是有错..

[!] /usr/bin/git clone http://git.oschina.net/akuandev/Specs.git master
xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun

最后的解决方法：

sudo xcode-select -switch /Applications/Xcode-beta.app/Contents/Developers

后面的地址你可以打开Xcode显示包内容，找到那个文件夹拖到终端里面比较不容易错。

CocoaPods 0.38.0.beta.2 is available.
To update use: `gem install cocoapods --pre`
[!] This is a test version we'd love you to try.

For more information see http://blog.cocoapods.org
and the CHANGELOG for this version http://git.io/BaH8pQ.


CocoaPods 0.38.0.beta.2 is available.
To update use: `gem install cocoapods --pre`
[!] This is a test version we'd love you to try.

For more information see http://blog.cocoapods.org
and the CHANGELOG for this version http://git.io/BaH8pQ.

最后终于修成正果..