Drush (http://www.drush.org/en/master/) is a command-line shell and Unix-scripting interface that allows us to interact with Drupal. Drush gives us the ability to use the command line to accomplish tasks quickly, without the need to rely on the Drupal admin UI. As part of the composer install, our project has the latest version of Drush installed automatically.
Executing a Drush command is typically as easy as typing the word drush within a Terminal window.
However, the challenge of having a per-project instance of Drush is in the way we are forced to currently execute Drush commands. Since the drush executable is located within the projects /vendor/bin/drush folder, if we are within the root of our project, we execute drush by entering the following within the Terminal window:
./vendor/bin/drush
The problem is the path can easily change; if, for instance, we are in the /web root, the same command would be:
../vendor/bin/drush
Notice the two dots indicating one must traverse up a level to locate the /vendor folder.
This is not ideal when we will be using Drush quite frequently to perform various tasks. We can resolve this in a couple of different ways.