SHELL

update brew

First update all package definitions (formulae) and Homebrew itself:
brew update

Upgrade everything with:
brew upgrade

You can now list which of your installed packages (kegs) are outdated with:
brew outdated

brew update package

brew upgrade mongodb

brew update

brew update # Get most recent versions of available formulae and casks
brew outdated # Lists the outdated installed formulae and casks
brew upgrade # Upgrade the packages listed by brew outdated
brew upgrade <formula or cask> # Upgrade a specific formula or cask

brew update

#This updates homebrew itself.
brew update
#You can then upgrade all individual packages and formula with the following:
brew upgrade