rm -rf /usr/local/etc/bash_completion.d/brew
rm -rf /usr/local/share/zsh/site-functions/_brew
rm -rf /usr/local/share/man/man1/brew.1
rm -rf /usr/local/share/doc/homebrew
brew update


ymdeMacBook-Pro:~ ym$ brew updateAlready up-to-date. 

brew update          # Update Homebrew's information
brew outdated # See which software can be upgraded
brew upgrade <xxx> # If you don't want to upgrade all of them, then upgrade the specified ones like this

brew upgrade; brew cleanup # If you want to upgrade them all, just upgrade them and clean them up