What Is $LOAD_PATH (also known as $:)

I have come across $LOAD_PATH many times and have always skipped over it, never quite understanding what it meant. Well, that is, until recently. The project that I am working on forced me to take a closer look. And once I did, like most things, it really wasn’t that difficult at all.

The first thing to understand is what it refers to. Quite simply $LOAD_PATH is what Ruby uses to determine which directories to look in when you use require in your code. In other words, $LOAD_PATH contains nothing more than lots of directories. Easy, huh?

The second thing you should know is how to reference it. You can refer to $LOAD_PATH in two ways. The first way is to simply call it by its name, $LOAD_PATH.

The second way is to use the predefined variable, $:

Both mean the exact same thing.

Finally to see it in action, here is an example of adding a directory to $LOAD_PATH

$: << File.expand_path('../', __FILE__)

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