Install Mac OSX El Capitan to a USB stick via CLI

On the command line, copy and paste the following.  NOTE: Substitute the path of the actual USB stick in place of  /Volumes/:

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/ --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app

Sourced from:
http://www.macworld.com/article/2981585/operating-systems/how-to-make-a-bootable-os-x-10-11-el-capitan-installer-drive.html