Ruby on rails RVM&；自制问题

我最近在终端中打开了一个旧项目，收到以下消息

 ruby-2.0.0-p598 is not installed.
 To install do: 'rvm install ruby-2.0.0-p598'

然后我运行了rvm install rvm install ruby-2.0.0-p598并收到了这个消息

 Searching for binary rubies, this might take some time.
 No binary rubies available for: osx/10.10/x86_64/ruby-2.0.0-p598.
 Continuing with compilation. Please read 'rvm help mount' to get more information on binary rubies.
 Checking requirements for osx.
 /usr/local/bin/brew: /usr/local/Library/brew.rb:/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby: bad interpreter: No such file or directory
 /usr/local/bin/brew: line 21: /usr/local/Library/brew.rb: Undefined error: 0
 ERROR: '/bin' is not writable - it is required for Homebrew, try 'brew doctor' to fix it!
 Requirements installation failed with status: 1.

然后我运行brew doctor并收到此消息

 /usr/local/bin/brew: /usr/local/Library/brew.rb: /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby: bad interpreter: No such file or directory
 /usr/local/bin/brew: line 21: /usr/local/Library/brew.rb: Undefined error: 0

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这里发生了什么以及如何解决此问题？

sudo chown-R用户名：group/usr/local请再次尝试brew doctor。

如果将该命令放入与其他指令分开的代码块中，效果会更好。这将起到什么作用@阿杰恩