June Developer Challenge - CAP Knowledge - Task 06 - Project specific configuration

[qmacro]

The "effective" configuration for a given project is made up from values that can be taken from a number of different source locations, shown here:

There are built-in defaults, user-specific defaults, static and user-specific project settings and more. These can be specified in, and will be retrieved from, various files and environment variable values.

Regard this sample configuration section:

"cds": {
  "requires": {
    "db": "sql"
  }
}

This value of sql as the kind of database requires can also be specified on the command line of Unix and Unix-like systems (anything other than Windows, effectively) using an environment variable.

What is the name of that environment variable (hint: like most environment variables, it will be in ALL_CAPS)?

This is a question from the June Developer Challenge on CAP Knowledge. And don't forget: always submit your answer as a hash, on its own - read the Taking part section of the intro post for more info. At the end of today, this question will be updated with links to further reading on this topic.