Install Drush 7 for Drupal 7 on Mac OS X
The Tutorial Shows You Step-by-Step How-to Install Drush Command Line Interface for Drupal 7 on Mac OS X 10.10 Yosemite Desktop.
Drush is a command line shell and Unix scripting interface for Drupal. If you are unfamiliar with shell scripting, reviewing the documentation for your shell (e.g. man bash) or reading an online tutorial (e.g. search for “bash tutorial”) will help you get the most out of Drush.
Open a Terminal Shell Emulator
Applications > Utilities > Terminal
(Press “Enter” to Execute Commands)
Install PHP5 Composer for Mac OS X:Installing Composer on Mac
Installing Drush CLi for Drupal8 on Mac OS X
composer global require drush/drush:dev-master
Insert Drush into User Path
echo "export PATH=$PATH:$HOME/.composer/vendor/bin" >> $HOME/.bashrc
Testing Drush Installation
Getting Started with Drush 7 CLI Commands:Drush 7 Commands Quick-Start