lix-project/lix
20
55
Fork 31
Code Issues 344 Code Review (Gerrit) Projects 3 Releases Wiki Activity

Merge pull request #8314 from fricklerhandwerk/doc-builtins

Browse source 
reword documentation on `builtins`
This commit is contained in:
Théophane Hufschmitt 2023-05-12 13:13:32 +02:00 committed by GitHub
parent 643b8d2126 69a0e6f86c
commit 491fabda49
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
1 changed files with 15 additions and 16 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

31
doc/manual/src/language/builtin-constants.md
View file

@ -1,20 +1,19 @@
# Built-in Constants # Built-in Constants
Here are the constants built into the Nix expression evaluator: These constants are built into the Nix language evaluator:
- `builtins`\ - [`builtins`]{#builtins-builtins} (attribute set)
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.,
```nix
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`]{#builtins-currentSystem}\ Contains all the [built-in functions](./builtins.md) and values, in order to avoid polluting the global scope.
The built-in value `currentSystem` evaluates to the Nix platform
identifier for the Nix installation on which the expression is being 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:
evaluated, such as `"i686-linux"` or `"x86_64-darwin"`.
```nix
if builtins ? getEnv then builtins.getEnv "PATH" else ""
```
- [`builtins.currentSystem`]{#builtins-currentSystem} (string)
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"`.