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nix-super/doc/manual/src/expressions/builtin-constants.md
regnat 31313d1401 Replace the trailing markdown spaces by a backslash 
They are equivalent according to
<https://spec.commonmark.org/0.29/#hard-line-breaks>,
and the trailing spaces tend to be a pain (because the make git
complain, editors tend to want to remove them − the `.editorconfig`
actually specifies that − etc..).
2021-04-23 14:37:21 +02:00

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Built-in Constants

Here are the constants built into the Nix expression evaluator:

  • builtins
    The set builtins contains all the built-in functions and values. You can use builtins to test for the availability of features in the Nix installation, e.g.,

    if builtins ? getEnv then builtins.getEnv "PATH" else ""

    This allows a Nix expression to fall back gracefully on older Nix installations that don’t have the desired built-in function.

  • builtins.currentSystem
    The built-in value currentSystem evaluates to the Nix platform identifier for the Nix installation on which the expression is being evaluated, such as "i686-linux" or "x86_64-darwin".