Install Carto.js (CartoCSS compiler written in Javascript) to use from the command line on OS X

install-carto.sh

# First install the latest version of Node.js if you don't already have node.js v0.8.x
# WARNING: do not use the .pkg installer for node. A bug in the installer will break
# later installs causing errors like "no suitable image found.  Did find: /path/to/some/lib: mach-o, but wrong architecture"

# install node either from source or from homebrew. Here we use homebrew:
brew install node

# Then make sure /usr/local/bin is on your PATH
export PATH=/usr/local/bin:$PATH

# Next install carto globally with the -g flag
npm install -g carto millstone

# Then, if you've used homebrew to install node/npm put the bin directory on your path
export PATH=/usr/local/share/npm/bin/:$PATH

# Make sure it installed okay:
$ carto -v
carto 0.9.4 (Carto map stylesheet compiler)

# Make sure compiling MSS styles are working:
$ echo 'Map {}' > style.mss
$ carto style.mss
<Style name="layer" filter-mode="first" >
</Style>

# Then compile your tilemill project to mapnik xml
$ carto ~/Documents/MapBox/project/your_map/project.mml > mapnik.xml