builtins.import

Takes 1 arguments

path

Load, parse, and return the Nix expression in the file path.

Note

Unlike some languages, import is a regular function in Nix.

The path argument must meet the same criteria as an interpolated expression.

If path is a directory, the file default.nix in that directory is used if it exists.

Example

$ echo 123 > default.nix

Import default.nix from the current directory.

import ./.

123

Evaluation aborts if the file doesn’t exist or contains an invalid Nix expression.

A Nix expression loaded by import must not contain any free variables, that is, identifiers that are not defined in the Nix expression itself and are not built-in. Therefore, it cannot refer to variables that are in scope at the call site.

Example

If you have a calling expression

rec {
  x = 123;
  y = import ./foo.nix;
}

then the following foo.nix will give an error:

# foo.nix
x + 456

since x is not in scope in foo.nix. If you want x to be available in foo.nix, pass it as a function argument:

rec {
  x = 123;
  y = import ./foo.nix x;
}

and

# foo.nix
x: x + 456

The function argument doesn’t have to be called x in foo.nix; any name would work.

Noogle also knows

import :: Path -> a