brew update失敗提示：/System/Library/Frameworks/Ruby.framework/的解決方法

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文章連接：http://www.cnblogs.com/wolfray/p/8040701.html

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想用brew安裝wget，可是提示失敗，而後想先 brew update，而後再從新試一下，結果在brew update後出現了這個狀況：

$ brew update
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- mach (LoadError) from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require' from /usr/local/Library/Homebrew/extend/pathname.rb:2:in `<top (required)>' from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require' from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require' from /usr/local/Library/Homebrew/global.rb:3:in `<top (required)>' from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require' from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require' from /usr/local/Library/brew.rb:16:in `<main>'

無論執行什麼brew命令提示依舊，這種狀況多發生在 El Capitan系統上，緣由大概是更新失敗，下面是stackoverflow找到的答案，親測有效：

The problem mainly occurs after updating OS X to El Capitan (OS X 10.11). This is mainly because of file permission issues with file El Capitan’s new SIP process. Try changing permissions of/usr/local directory.

sudo chown -R $(whoami):admin /usr/local 

若是運行完上面的命令尚未起做用的話，那麼再運行下面的命令應該就能夠了。這多是由於homebrew尚未升級的緣由。

• 1. 首先打開終端
  2. $ cd /usr/local  
  3. $ git reset --hard  
  4. $ git clean -df
  5. $ brew update