chflags nohidden ~/Library/
chflags hidden ~/Library
http://osxdaily.com/2011/07/04/show-library-directory-in-mac-os-x-lion/
defaults write com.apple.finder AppleShowAllFiles -bool YES killall Finder
defaults write com.apple.finder AppleShowAllFiles -bool NO killall finder
http://www.macosxtips.co.uk/index_files/quickly-show-hidden-files.php