网上搜了篇文章，介绍iOS的越狱开发，其中提到了要给Xcode安装command line tools，以前从没听过这个工具，然后就google了下。

关于Xcode Command Line Tools的介绍：

https://developer.apple.com/library/ios/technotes/tn2339/_index.html

What is the Command Line Tools Package?

The Command Line Tools Package is a small self-contained package available for download separately from Xcode and that allows you to do command line development in OS X. It consists of two components: OS X SDK and command-line tools such as Clang, which are installed in /usr/bin.

Command Line Tools的安装

这篇文章更为详细的介绍了Command Line Tools的安装

http://railsapps.github.io/xcode-command-line-tools.html

但是我按照网上说的方法，在Xcode >>Preferences >>download里面并没有看到有command line tools的下载，然后就开始按照上面帖子里面介绍的试一下各种命令。

在终端里面输入whoami

果然给我输出了我的Mac的名字，好神奇！

当我输入

$ xcode-select -p

确实返回了

/Applications/Xcode.app/Contents/Developer

说明我的Xcode安装的是个全版本的

接下来就到了安装Command Line Tools了

继续在终端里面输入：

$ xcode-select --install

Verify that you’ve successfully installed Xcode Command Line Tools:

$ xcode-select -p
/Library/Developer/CommandLineTools

Just to be certain, verify that gcc is installed:

$ gcc --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn)
Target: x86_64-apple-darwin14.0.0
Thread model: posix

证明确实Command Line Tools工具已经正确安装了，接下来就开始越狱的开发吧！