These constants are built into the Nix language evaluator:
Contains all the built-in functions and values, in order to avoid polluting the global scope.
Since built-in functions were added over time, testing for attributes in
builtinscan be used for graceful fallback on older Nix installations:
if builtins ? getEnv then builtins.getEnv "PATH" else ""
The built-in value
currentSystemevaluates to the Nix platform identifier for the Nix installation on which the expression is being evaluated, such as