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  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Using Nix\n",
    "\n",
    "This tutorial given an introduction to the basic `nix-*` commands."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Building with `nix-build`\n",
    "\n",
    "The `nix-build` command is used for building recipes, also known as derivations. The resulting build artifacts are packages that can be installed or copied elsewhere.\n",
    "\n",
    "In the following example we create a `recipe.nix` file. In this case,\n",
    "our recipe is simple: we fetch the latest version of NixOS 19.09 and build\n",
    "a package from it, `hello`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "%%file recipe.nix\n",
    "with import (fetchTarball \"channel:nixos-19.09\") {};\n",
    "hello"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-build recipe.nix"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The store path shows where the build is cached. A symbolic link to that path is also created"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! ls -l result"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can run the `hello` command that is provided by it"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! result/bin/hello"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Managing channels with `nix-channel`\n",
    "\n",
    "Nix has the concept of channels. A channel is essentially a location providing Nix expressions. The Nixpkgs project offers various channels.\n",
    "\n",
    "The following lists the currently configured channels"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-channel --list"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We will now install a channel"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-channel --add https://github.com/NixOS/nixpkgs-channels/archive/nixos-19.09.tar.gz nixos"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "and can check it is configured"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-channel --list"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To use the channel, don't forget to update it. This will fetch the latest Nix expression on the location the channel points to."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-channel --update"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Installing with `nix-env`\n",
    "\n",
    "Nix has the concept of profiles where users can install packages in. The `nix-env` command is used for installing packages. Users have a default profile, let's see if anything is installed for the current user"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-env --query"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can now install `hello` in our profile. That way, the application will remain available. Let's install it from our `recipe.nix` file."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-env -i -f recipe.nix"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can now see it is installed"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-env --query"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "and that we can execute it"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! hello"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can install the same package but from the channel we configured. Note the package of interest, `hello`, is an attribute of the Nix expression that the channel `nixos` corresponds to"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-env -iA nixos.hello"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Instead of installing from a local file, we can also fetch an expression. It's possible to point to any Nix expression or archive containing Nix expressions."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-env -iA hello -f https://github.com/NixOS/nixpkgs-channels/archive/nixos-19.09.tar.gz"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "In the example we actually fetched a channel, for which a short-hand notation exists"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "! nix-env -iA hello -f \"channel:nixos-19.09\""
   ]
  }
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