Installing Emacs on OS X
OS X comes with a preinstalled version of Emacs, but alas it is the outdated Emacs 22. Fortunately, obtaining a newer release is really simple. There are several popular ways to do it.
Emacs 24
As a binary package
Simply download a binary from Emacs for OSX.
The above binary distribution bundled with up-to-date versions AUCTeX, ESS and a few other useful tools is available from Vincent Goulet's web site.
MacPorts
If you have MacPorts installed, you can just do:
$ sudo port install emacs
to install Emacs 24. The MacPorts installer updates your PATH environment variable, so the MacPorts build of Emacs should be found by your shell before the (outdated) build that comes with Mac OS when you type 'emacs'. If you prefer the Emacs.app build, that's available by executing:
$ sudo port install emacs-app
Homebrew
Emacs 27 is also available via [1]. Just type the following incantation in your shell and you’re done:
$ brew update
$ brew install emacs
Chances are good you have an older version of Emacs installed by default with OS X. It's suggested you to remove that older Emacs version to avoid conflicts with the new one. Do this:
$ sudo rm /usr/bin/emacs
$ sudo rm -rf /usr/share/emacs
That’s all folks! You may now proceed to the configuration section.
Homebrew recommended by brew
Brew now recommends emacs to be installed as
brew cask install emacs
But that doesn't create /usr/local/bin/emacs.
You may follow Emacs for Mac OS X, Tips on how to create scripts for running emacs and emacsclient.
Rudix
Emacs is easy to install directly from Rudix as a .pkg or with the Rudix command line tool:
% sudo rudix install emacs
Emacs 27
Binaries for Emacs 27 are still available from Emacs for OSX.
Aquamacs
A near-OS-X-native port of GNU Emacs, integrating Emacs with all the features of Mac OS X. Available here. As of January 2015, the latest version (3.2) is based on Emacs 24.4. Comes bundled with some handy packages like AUCTeX.