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69a0e6f86c
- add anchor to `builtins` - add type information - reword description of `builtins` to offer more information concisely
19 lines
764 B
Markdown
19 lines
764 B
Markdown
# Built-in Constants
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These constants are built into the Nix language evaluator:
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- [`builtins`]{#builtins-builtins} (attribute set)
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Contains all the [built-in functions](./builtins.md) and values, in order to avoid polluting the global scope.
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Since built-in functions were added over time, [testing for attributes](./operators.md#has-attribute) in `builtins` can be used for graceful fallback on older Nix installations:
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```nix
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if builtins ? getEnv then builtins.getEnv "PATH" else ""
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```
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- [`builtins.currentSystem`]{#builtins-currentSystem} (string)
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The built-in value `currentSystem` evaluates to the Nix platform
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identifier for the Nix installation on which the expression is being
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evaluated, such as `"i686-linux"` or `"x86_64-darwin"`.
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