mac下brew更新失败,大神们帮忙看看

我在终端执行了代码brew update,结果出现了下面的问题,大神们帮忙看看这是怎么了,怎么解决呢?

wanglaoshideMacBook-Pro:~ apple$ brew update
    
    /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 `<top (required)>'
    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 `<top (required)>'
    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 `<main>'

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貌似彻底坏了，你试试brew doctor，如果还是出错的话重新安装brew吧。