2020-06-14 14:16:23 +00:00
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#+Title: How I use nix
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#+Author: Yann Esposito
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#+Email: yann@esposito.host
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#+Date: [2020-06-14 Sun]
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2021-04-27 13:21:06 +00:00
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#+KEYWORDS: nix programming
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2020-06-25 12:22:58 +00:00
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#+DESCRIPTION: In this article I explain how I use nix. As a brew replacement, as home environment manager, to have reproductible dev environment.
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2020-06-14 14:16:23 +00:00
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#+LANGUAGE: en
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#+LANG: en
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#+OPTIONS: H:5 auto-id:t toc:nil
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#+STARTUP: showeverything
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2020-06-14 21:52:09 +00:00
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Have you ever written a small script and you update your system and this
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stop working?
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Have you copied your tool/script to another machine it doesn't work because
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some dependency is missing?
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Have you tried to sync your dotfiles to another env and there are a few
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details not working? Some missing dependency?
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If the answer is yes, then [[https://nixos.org/nix][nix]] can help.
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** Scripts
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:PROPERTIES:
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:CUSTOM_ID: scripts
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:END:
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2020-06-14 14:16:23 +00:00
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2020-06-14 21:52:09 +00:00
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Suppose you want to write a portable script.
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For example, the script I use to minify my CSS.
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Here it is:
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2020-06-14 14:16:23 +00:00
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2020-06-14 21:52:09 +00:00
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#+begin_src shell
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#!/usr/bin/env nix-shell
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#!nix-shell --pure
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#!nix-shell -i bash
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#!nix-shell -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz"
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#!nix-shell -p bash minify
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minify "$1" > "$2"
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#+end_src
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So let's analyze each line of the header block:
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- ~#!/usr/bin/env nix-shell~ :: basic, use ~nix-shell~ to run the script.
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- ~#!nix-shell --pure~ :: only use dependencies installed in this nix shell
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environment. A bit as if the PATH environment variable was emptied.
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- ~#!nix-shell -i bash~ :: tell ~nix-shell~ to run ~bash~
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- ~#!nix-shell -I nixpkgs="https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz"~ ::
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pin the nixpkgs using this archive.
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- ~#!nix-shell -p bash minify~ :: install ~bash~ and ~minify~ in the nix shell.
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Now if the script is run on a machine with ~nix~ installed you can be
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pretty sure it will work as expected.
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Even if I update my OS and I forget about this script for a few years.
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As long as I can install nix on the new system and I could download the tar
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file the script will be run the same way as the day I wrote it.
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2020-06-14 22:02:26 +00:00
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**Remark**:
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You can use any shell (like ~fish~, ~zsh~) but also other languages
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~python~, ~haskell~, etc...
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2020-06-14 21:52:09 +00:00
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** Temporary working env
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:PROPERTIES:
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:CUSTOM_ID: temporary-working-env
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:END:
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Quite often, I need to do something, and run a specific command that need
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me to install a very specific command.
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And I'm pretty sure I will not use this tool ever again.
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For those cases, what I do, is generally run my command directly with a
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fresh ~nix-shell~.
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#+begin_src shell
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> nix-shell -p httpie
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[nix-shell:~]$ ... here I can use httpie ...
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#+end_src
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2020-06-14 14:16:23 +00:00
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2020-06-14 22:45:51 +00:00
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If I don't use ~httpie~ for a while it will be garbage collected
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eventually.
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2020-06-14 14:16:23 +00:00
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** Home Manager
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:PROPERTIES:
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:CUSTOM_ID: home-manager
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:END:
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2020-06-14 21:52:09 +00:00
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A few years ago I used =brew= to install the tools I need.
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With =nix= you can install a new tool with ~nix-env -i~ instead of ~brew install~.
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Still recently I prefer to use [[https://github.com/rycee/home-manager][home-manager]].
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The main advantage is that it is even more reproductible and can easily be
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shared accross different machines.
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2020-06-14 14:16:23 +00:00
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2020-06-14 21:52:09 +00:00
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Mainly when I need a new binary I add it in a description list in the file
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=~/.config/nixpkgs/home.nix=.
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It looks like this:
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2020-06-14 14:16:23 +00:00
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#+begin_src nix
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2020-06-14 21:52:09 +00:00
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home.packages = with pkgs; [
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# emacs
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emacsMacport
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imagemagick
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gnupg
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# shell
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direnv
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...
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];
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#+end_src
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then I simply run ~home-manager switch~ and I've got all those tools in my env.
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*** Pinning the packages
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:PROPERTIES:
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:CUSTOM_ID: pinning-the-packages
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:END:
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#+begin_src nix
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{ config, pkgs, ... }:
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let
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# ...
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pkgs = import (fetchGit {
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name = "nixpkgs20";
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url = "https://github.com/NixOS/nixpkgs";
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# obtained via
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# git ls-remote https://github.com/NixOS/nixpkgs nixpkgs-20.03-darwin
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ref = "refs/heads/nixpkgs-20.03-darwin";
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rev = "58f884cd3d89f47672e649c6edfb2382d4afff6a";
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}) {};
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# ...
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in {
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# ...
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}
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2020-06-14 14:16:23 +00:00
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#+end_src
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2020-06-14 21:52:09 +00:00
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*** Specific tools
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:PROPERTIES:
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:CUSTOM_ID: specific-tools
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:END:
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2020-06-16 22:10:49 +00:00
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There are a few noticiable artifacts here:
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2020-06-14 14:16:23 +00:00
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2020-06-14 21:52:09 +00:00
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The first one is ~weechat~ is a very specify build of weechat with the
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2020-06-14 22:02:26 +00:00
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plugin I need.
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2020-06-16 22:10:49 +00:00
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For that I created a new directory =weechat-with-weeslack= containing a
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=default.nix=:
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2020-06-14 14:16:23 +00:00
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#+begin_src nix
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2020-06-16 22:10:49 +00:00
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{ pkgs, ...}:
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pkgs.weechat.override {
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configure = { availablePlugins, ... }: {
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# plugins = with availablePlugins; [ python perl guile ];
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scripts = with pkgs.weechatScripts; [ wee-slack ];
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};
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2020-06-14 21:52:09 +00:00
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}
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2020-06-14 14:16:23 +00:00
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#+end_src
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2020-06-16 22:10:49 +00:00
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And in my =home.nix= I use:
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#+begin_src nix
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weechat-with-weeslack = import ./weechat-with-weeslack {
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inherit pkgs;
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};
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#+end_src
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2020-06-14 22:02:26 +00:00
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Even if this looks cryptic.
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The important detail is just that there exists a way to say to nix I'd like
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to use weechat (an IRC client) with the wee-slack client (which uses python).
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2020-06-16 22:10:49 +00:00
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And nix handle the rest for me without any conflict.
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2020-06-14 14:16:23 +00:00
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2020-06-14 21:52:09 +00:00
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*** Another nice tool is =sws=
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:PROPERTIES:
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:CUSTOM_ID: another-nice-tool-is--sws-
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:END:
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I use macOS so even though I'm using a darwin focused nixpkgs
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sometimes a few package can be broken and can't be installed.
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That occurred with [[https://hackage.haskell.org/package/sws][=sws=]] during the upgrade to 20.03 on darwin.
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This is a simple tool that need haskell to be compiled locally and
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installed.
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Here is how I could install it:
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2020-06-14 14:16:23 +00:00
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#+begin_src nix
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let
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...
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rel19 = import (fetchGit {
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name = "nixpkgs19";
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url = "https://github.com/NixOS/nixpkgs";
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ref = "refs/heads/nixpkgs-19.09-darwin";
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rev = "2f9bafaca90acd010cccd0e79e5f27aa7537957e";
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}) {};
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2020-06-16 22:10:49 +00:00
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haskellDeps = ps: with ps; [
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base
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protolude
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tidal
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shake
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rel19.haskellPackages.sws
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];
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ghc = pkgs.haskellPackages.ghcWithPackages haskellDeps;
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2020-06-14 14:16:23 +00:00
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...
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in
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home.packages = with pkgs; [
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...
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ghc
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...
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]
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#+end_src
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So I used the older version from 19.09.
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2020-06-16 22:10:49 +00:00
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** Dev environment
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:PROPERTIES:
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:CUSTOM_ID: dev-environment
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:END:
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When working on a project.
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You can produce a pretty good local environment.
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For example, for my blog, I only use emacs and a few shell scripts.
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Still I needed to fix a few binaries, like the correct ~date~ via
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~coreutils~.
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And also I use ~html-xml-utils~ to easily deal with html/xml parsing.
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I use it to generate my RSS xml file.
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So I have a ~shell.nix~ files at the root of my project:
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#+begin_src nix
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{ pkgs ? import (fetchTarball https://github.com/NixOS/nixpkgs/archive/19.09.tar.gz) {} }:
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let my_aspell = pkgs.aspellWithDicts(p: with p; [en fr]);
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in
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pkgs.mkShell {
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buildInputs = [ pkgs.coreutils
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pkgs.html-xml-utils
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pkgs.zsh
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pkgs.perl
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pkgs.perlPackages.URI
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pkgs.minify
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pkgs.haskellPackages.sws
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pkgs.cacert
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];
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}
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#+end_src
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So I just need to launch ~nix-shell~ and I have my environment.
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A nice addition is to use direnv[fn:direnv] which support ~nix-shell~ by putting
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~use_nix~ inside the ~.envrc~ at the root of the project.
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But by default invoking ~nix-shell~ can take a few seconds everytime.
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But we can do even better by using lorri[fn:lorri].
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I start the lorri daemon in my ~StartupItems~ mainly I simply created
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the file =~/Library/LaunchAgents/com.github.target.lorri.plist=:
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#+begin_src xml :tangle com.github.target.lorri.plist :mkdirp t
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
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<plist version="1.0">
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<dict>
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<key>Label</key>
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<string>com.github.target.lorri</string>
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<key>ProgramArguments</key>
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<array>
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<string>/bin/zsh</string>
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<string>-i</string>
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<string>-c</string>
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<string>$HOME/.nix-profile/bin/lorri daemon</string>
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</array>
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<key>StandardOutPath</key>
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<string>/var/tmp/lorri.log</string>
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<key>StandardErrorPath</key>
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<string>/var/tmp/lorri.log</string>
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<key>RunAtLoad</key>
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<true/>
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<key>KeepAlive</key>
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<true/>
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</dict>
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</plist>
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#+end_src
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And started the daemon with:
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#+begin_src bash
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launchctl load ~/Library/LaunchAgents/com.github.target.lorri.plist
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#+end_src
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~lorri~ takes care of keeping a cache and watch my configuration change by
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project.
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This makes the call to ~direnv~ almost instantaneous and seemless.
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I just changed the content of my ~.envrc~ with:
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#+begin_src shell
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eval "$(lorri direnv)"
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#+end_src
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And of course this would work the same way with more complex ~shell.nix~.
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Typically for Haskell projects.
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[fn:direnv] https://direnv.net
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[fn:lorri] https://github.com/target/lorri
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2020-06-14 21:52:09 +00:00
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** Install
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:PROPERTIES:
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:CUSTOM_ID: install
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:END:
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2020-06-16 22:10:49 +00:00
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So you would like to use nix too?
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2020-06-14 21:52:09 +00:00
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First, let's start by the bad news.
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Recent macOS security policy made nix a bit harder to install on a mac.
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See [[https://hydra.nixos.org/build/119559243/download/1/manual/#sect-macos-installation][macOS Installation instructions]].
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Once you have nix installed you should update the nix-channel.
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Mainly a nix-channels is where are the definitions of all the packages.
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See [[https://hydra.nixos.org/build/119559243/download/1/manual/#sec-channels][nixOS documentation]].
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2020-06-14 14:16:23 +00:00
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