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# nix-forecast
Check the forecast for today's Nix builds with a blazingly fast (🚀🔥🦀) CLI
## Usage
```
Check the forecast for today's Nix builds
Usage: nix-forecast [OPTIONS] [INSTALLABLES]...
Arguments:
[INSTALLABLES]... A list of Nix installables to look for. If not given, all paths in nixpkgs are checked
Options:
-c, --configuration <CONFIGURATION> Flake reference pointing to a NixOS or nix-darwin configuration
-b, --binary-cache <BINARY_CACHE> URL of the substituter to check [default: https://cache.nixos.org]
-f, --flake <FLAKE> Flake reference of nixpkgs (or other package repository) [default: nixpkgs]
-s, --show-missing Show a list of store paths not found in the substituter
-h, --help Print help
-V, --version Print version
```
## Examples
### Flake installables
```sh
nix-forecast nixpkgs#{hello,gcc,clang,nrr}
```
### NixOS configuration
```sh
nix-forecast .#nixosConfigurations.myMachine
```
### nix-darwin configuration
```sh
nix-forecast .#darwinConfigurations.myMac
```
## Why?
Finding out if paths are cached can be a bit troublesome in Nix, with commands like `nix build --dry-run`
being the only solution a lot of the time. Meanwhile in the world of [Guix](https://guix.gnu.org/), they have
had the `guix weather` command to do this for ages! This project aims to bring the power of that command right
to Nix
### What about `nix-weather`?
`nix-weather` is another project with a similar goal of bringing some of the features of `guix weather` to
Nix. However, it does introduce it's own spin on things and has much more of a focus on NixOS configurations.
In contrast, `nix-forecast` aims to be as close to the Guix command as possible, while also introducing more
generic support for [Flake](https://nix.dev/concepts/flakes) references, NixOS *and* nix-darwin
configurations, better error messages, and a (subjectively) more comfortable interface
I've also made it slightly faster :p
```
$ hyperfine --warmup 1 './result/bin/nix-weather --name glados --config ~/flake' './target/release/nix-forecast --configuration ~/flake#nixosConfigurations.glados'
Benchmark 1: ./result/bin/nix-weather --name glados --config ~/flake
Time (mean ± σ): 11.387 s ± 0.646 s [User: 3.422 s, System: 1.663 s]
Range (min … max): 10.490 s … 12.569 s 10 runs
Benchmark 2: ./target/release/nix-forecast --configuration ~/flake#nixosConfigurations.glados
Time (mean ± σ): 6.395 s ± 0.229 s [User: 0.992 s, System: 0.967 s]
Range (min … max): 6.231 s … 7.030 s 10 runs
Warning: Statistical outliers were detected. Consider re-running this benchmark on a quiet system without any interferences from other programs. It might help to use the '--warmup' or '--prepare' options.
Summary
./target/release/nix-forecast --configuration ~/flake#nixosConfigurations.glados ran
1.78 ± 0.12 times faster than ./result/bin/nix-weather --name glados --config ~/flake
```
## Inspired by...
- [guix weather](https://guix.gnu.org/manual/en/html_node/Invoking-guix-weather.html)
- [nix-weather](https://github.com/cafkafk/nix-weather/)
- [My much slower version in Fish](https://discourse.nixos.org/t/how-to-find-uncached-dependencies-of-a-closure/45385)
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