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90 lines
2.7 KiB
Text
90 lines
2.7 KiB
Text
= The hello-flake repo
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Let's clone the repository and see how the flake is defined.
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....
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$ git clone https://codeberg.org/mhwombat/hello-flake
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$ cd hello-flake
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$ ls
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....
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This is a simple repo with just a few files. Like most git repos, it
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includes `LICENSE`, which contains the software license, and `README.md`
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which provides information about the repo.
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The `hello-flake` file is the executable we ran earlier.
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This particular executable is just a shell script, so we can view it.
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It's an extremely simple script with just two lines.
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[source,bash,linenums]
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.hello-flake
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....
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$# cat hello-flake
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....
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Now that we have a copy of the repo, we can execute this script
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directly.
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....
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$ ./hello-flake
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....
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Not terribly exciting, I know. But starting with such a simple package
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makes it easier to focus on the flake system without getting bogged down
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in the details. We'll make this script a little more interesting later.
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Let's look at another file. The file that defines how to package a flake
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is always called `flake.nix`.
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[source,nix,linenums]
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.flake.nix
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....
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$# cat flake.nix
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....
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If this is your first time seeing a flake definition, it probably looks
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intimidating.
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Flakes are written in the Nix language, introduced in an earlier chapter.
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However, you don't really need to know Nix to follow this example.
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For now, I'd like to focus on the inputs section.
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[source,nix]
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....
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inputs = {
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nixpkgs.url = "github:NixOS/nixpkgs";
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flake-utils.url = "github:numtide/flake-utils";
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};
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....
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There are just two entries, one for `nixpkgs` and one for `flake-utils`.
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The first one, `nixpkgs` refers to the collection of standard software
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packages that can be installed with the Nix package manager. The second,
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`flake-utils`, is a collection of utilities that simplify writing
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flakes. The important thing to note is that the `hello-flake` package
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_depends_ on `nixpkgs` and `flake-utils`.
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Finally, let's look at `flake.lock`, or rather, just part of it.
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[source,,linenums]
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.flake.lock
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....
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$# head -n 40 flake.lock
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. . .
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....
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If `flake.nix` seemed intimidating, then this file looks like an
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invocation for Cthulhu. The good news is that this file is automatically
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generated; you never need to write it. It contains information about all
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of the dependencies for the flake, including where they came from, the
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exact version/revision, and hash. This lockfile _uniquely_ specifies all
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flake dependencies, (e.g., version number, branch, revision, hash), so
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that _anyone, anywhere, any time, can re-create the exact same
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environment that the original developer used._
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No more complaints of "`but it works on my machine!`". That is the
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benefit of using flakes.
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////
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Good adoc0 scripts clean up after themselves.
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$ cd .. ; rm -rf hello-flake # clean up
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////
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