# Packages
Similar to [modules](../modules), the pkgs directory mirrors the upstream
[nixpkgs/pkgs][pkgs], and for the same reason; if you ever want to upstream
your package, it's as simple as dropping it into the nixpkgs/pkgs directory.

The only minor difference is that, instead of adding the `callPackage` call to
`all-packages.nix`, you just add it the the _default.nix_ in this directory,
which is defined as a simple overlay.

This overlay is set as the default `overlay` output attribute for the flake.
And all the packages are exported via `packages.<system>.<pkg-name>`, for all
the supported systems listed in the package's `meta.platforms` attribute.

And, as usual, every package in the overlay is also available to any NixOS
[host](../hosts).

## Example
pkgs/development/libraries/libinih/default.nix:
```nix
{ stdenv, meson, ninja, fetchFromGitHub, ... }:
let version = "r50";
in
stdenv.mkDerivation {
  pname = "libinih";
  inherit version;

  src = fetchFromGitHub {
    owner = "benhoyt";
    repo = "inih";
    rev = "${version}";
    hash = "sha256-GF+TVEysaXJxSBBjMsTr2IQvRKlzdEu3rlPQ88PE3nI=";
  };

  buildInputs = [ meson ninja ];

  mesonFlags = ''
    -Ddefault_library=shared
    -Ddistro_install=true
  '';

  meta = with stdenv.lib; {
    description = "Simple .INI file parser in C";
    homepage = "https://github.com/benhoyt/inih";
    maintainers = [ maintainers.nrdxp ];
    license = licenses.bsd3;
    platforms = platforms.all;
    inherit version;
  };
}
```

pkgs/default.nix:
```nix
final: prev: {
  libinih = prev.callPackage ./development/libraries/libinih { };
}
```

[pkgs]: https://github.com/NixOS/nixpkgs/tree/master/pkgs