pi@raspberrypi:~ $ brew install opencv
Updating Homebrew...
/home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- dbm (LoadError)
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/cache_store.rb:1:in `<top (required)>'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/formula.rb:1:in `<top (required)>'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/readall.rb:1:in `<top (required)>'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/tap.rb:2:in `<top (required)>'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/2.3.7/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/global.rb:145:in `<top (required)>'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/brew.rb:15:in `require_relative'
from /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/brew.rb:15:in
> `<main>'``