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address review comments
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Valentin Gagarin
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@ -15,8 +15,7 @@ But when *first* packaging existing software with Nix, it's common to encounter
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## Introduction
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In this tutorial, you'll create your first [Nix derivations](https://nix.dev/manual/nix/2.18/language/derivations) to package C/C++ software.
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This takes advantage of the [Nixpkgs Standard Environment](https://nixos.org/manual/nixpkgs/stable/#part-stdenv) (`stdenv`), which automates much of the work involved.
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In this tutorial, you'll create your first [Nix derivations](https://nix.dev/manual/nix/2.18/language/derivations) to package C/C++ software, taking advantage of the [Nixpkgs Standard Environment](https://nixos.org/manual/nixpkgs/stable/#part-stdenv) (`stdenv`), which automates much of the work involved.
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### What will you learn?
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@ -32,7 +31,7 @@ You'll encounter and address Nix error messages, build failures, and a host of o
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### How long does it take?
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Going through all the steps carefully will take ca. 60 minutes.
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Going through all the steps carefully will take around 60 minutes.
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## Your first package
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@ -41,10 +40,10 @@ Going through all the steps carefully will take ca. 60 minutes.
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TODO: link to the Nix manual glossary entry once it's in a released build:
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https://hydra.nixos.org/job/nix/master/build.x86_64-linux/latest/download/manual/glossary.html#package
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-->
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A _package_ is a loosely defined concept that refers to both a collection of files and other data, or a {term}`Nix expression` representing such a collection before it comes into being.
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Packages in Nixpkgs have conventional, mostly standardised structure, allowing them to be discovered in searches and composed in environments alongside other packages.
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A _package_ is a loosely defined concept that refers to either a collection of files and other data, or a {term}`Nix expression` representing such a collection before it comes into being.
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Packages in Nixpkgs have a conventional structure, allowing them to be discovered in searches and composed in environments alongside other packages.
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For the purposes of this tutorial, "package" means: a Nix language function that will evaluate to a derivation.
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For the purposes of this tutorial, a "package" is a Nix language function that will evaluate to a derivation.
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It will enable you or others to produce an artifact for practical use, as a consequence of having "packaged existing software with Nix".
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:::
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@ -58,10 +57,6 @@ stdenv.mkDerivation { };
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This is a function which takes an attribute set containing `stdenv`, and produces a derivation (which currently does nothing).
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:::{note}
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For Nix, a recipe to build a package is a function that takes references to – immutable – files and produces new files.
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:::
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### A package function
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GNU Hello is an implementation of the "hello world" program, with source code accessible [from the GNU Project's FTP server](https://ftp.gnu.org/gnu/hello/).
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@ -77,14 +72,13 @@ stdenv.mkDerivation {
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```
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Next, you will declare a dependency on the [latest version](https://ftp.gnu.org/gnu/hello/hello-2.12.1.tar.gz) of `hello` and instruct Nix to use `fetchzip`.
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It takes the URL to the file and a [SHA256 hash](https://en.wikipedia.org/wiki/SHA-2) of its contents.
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Next, you will declare a dependency on the latest version of `hello`, and instruct Nix to use `fetchzip` to download the [source code archive](https://ftp.gnu.org/gnu/hello/hello-2.12.1.tar.gz).
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:::{note}
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`fetchzip` can fetch [more archives](https://nixos.org/manual/nixpkgs/stable/#fetchurl) than just zip files!
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`fetchzip` can fetch [more archives](https://nixos.org/manual/nixpkgs/stable/#fetchurl) than just] zip files!
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:::
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The hash cannot be known until after the tarball has been downloaded and unpacked.
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The hash cannot be known until after the archive has been downloaded and unpacked.
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Nix will complain if the hash supplied to `fetchzip` is incorrect.
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It is common practice to supply a fake one with `lib.fakeSha256` and change the derivation definition after Nix reports the correct hash:
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@ -174,7 +168,7 @@ error:
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### Finding the file hash
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As expected, the incorrect file hash caused an error, and Nix helpfully provided the correct one.
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Substitute substitute it into `hello.nix` to replace `lib.fakeSha256`:
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In `hello.nix`, replace `lib.fakeSha256` with the correct hash:
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```nix
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# hello.nix
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@ -435,12 +429,15 @@ But the important bit for this tutorial is `fatal error: X11/Xlib.h: No such fil
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Determining from where to source a dependency is currently a somewhat involved, because package names don't always correspond to library or program names.
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You will need the `Xlib.h` headers from the `X11` C package, the Nixpkgs derivation for which is `libX11`, available in the `xorg` package set.
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There are multiple ways to figure this out:
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### `search.nixos.org`
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:::{tip}
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The easiest way to find what you need is on search.nixos.org/packages.
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:::
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### search.nixos.org
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Unfortunately in this case, [searching for `x11`](https://search.nixos.org/packages?query=x11) produces too many irrelevant results because X11 is ubiquitous.
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On the left side bar there is a list package sets, and [selecting `xorg`](https://search.nixos.org/packages?channel=23.11&buckets={%22package_attr_set%22%3A[%22xorg%22]%2C%22package_license_set%22%3A[]%2C%22package_maintainers_set%22%3A[]%2C%22package_platforms%22%3A[]}&query=x11) shows something promising.
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@ -459,7 +456,8 @@ Only clone the latest revision if you don't want to wait a long time:
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$ nix-shell -p git ripgrep
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[nix-shell:~]$ git glone https://github.com/NixOS/nixpkgs --depth 1
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```
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Nixpkgs is *huge*, therefore specify which subdirectory you want to search:
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To narrow down results, specify which subdirectory you want to search:
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```console
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[nix-shell:~]$ rg "x11 =" pkgs
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@ -500,8 +498,6 @@ pkgs/servers/x11/xorg/overrides.nix
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Consider using `nix-locate` from the [`nix-index`](https://github.com/nix-community/nix-index) tool to find derivations that provide what you need.
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You will need the `Xlib.h` headers from the `X11` C package, the Nixpkgs derivation for which is `libX11`, available in the `xorg` package set.
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### Adding package sets as dependencies
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Add this to your derivation's input attribute set and to `buildInputs`:
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