brew更新后不可用

昨天用brew安装了些程序后，不知道哪根筋不对，顺手brew update。

今天使用的时候显示：

---

$ brew

/Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- mach (LoadError)

from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'

from /usr/local/Library/Homebrew/extend/pathname.rb:2:in `'

from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'

from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'

from /usr/local/Library/Homebrew/global.rb:3:in `'

from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'

from /Library/Ruby/Site/2.0.0/rubygems/core_ext/kernel_require.rb:54:in `require'

from /usr/local/Library/brew.rb:15:in `'

---

stack overflow上的解决办法： homebrew not working on OSX

The problem mainly occurs after updating OS X to El Capitan (OS X 10.11) or macOS Sierra (macOS 10.12). This is mainly because of file permission issues with El Capitan’s or later macOS's new SIP process. Try changing permissions of /usr/local directory.

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

If it still doesn't work, use following steps and everything will be fine. This may be because homebrew is not updated.

1. open terminal  

2. $ cd /usr/local/Library/Homebrew  

3. $ git reset --hard  

4. $ git clean -df

5. $ brew update