http://xor.lonnen.com/2013/01/04/emacs-on-osx.html

Setting up OSX and iTerm2 for Emacs

January 04, 2013 by 

Chris Lonnen

I've decided to give Emacs a spin as my primary editor in January. Learning a new editor has been refreshing, but OSX got in my way a few times when I was setting things up. Many thanks are owed to James Long for helping me with that. I wanted to share some of my experience for other curious parties encountering similar problems.

First: a note on my environment. I use iTerm2 instead of the native Terminal.app and I highly recommend you install it right now if you haven't already. There is an older Emacs preinstalled on OSX, but since I've universally had trouble with other preinstalled dev tools I installed Emacs 24 via Homebrew. I used the optional --cocoa flag, though I run it exclusively in the terminal.

Emacs has two modifier keys used for issuing commands to the editor, referred to in the documentation as C- and M-, short for Command and Meta. By default these are control andoption on an Apple keyboard, respectively. This presents two problems: first, control is awkwardly placed and uncomfortable to use frequently; second, the option key already has OSX-level functionality.

To help save my pinky, I opened up System Preferences -> Keyboard and hit the Modifier Keys button. From this preference pane I remapped caps lock to ^ Control, which changes the functionality throughout the OS. Now C- is comfortably within reach of my hands from the home row.

The M- char still presented a problem though, as option + [other key] is interpreted into special characters. To fix this, I used an iTerm2 feature. In preferences, under profiles and in the keys tab you can specify either the right or left option keys to send +Esc instead, which Emacs will treat as M-. I chose to alter only my right control so that I could still use the left if I needed default behavior.

At that point I had both C- and M- working, but I found option uncomfortable to reach for all the time. Another iTerm2 preference, this one under keys, allowed me to swap right commandand right option keys. This is a little more comfortable to use frequently.