★ nix-env in a nutshell for basic usage in macOS

I am currently evaluating Nix as a replacement for Homebrew CLI apps in macOS¹. Others have previously written about this.

My goal is to keep a sane learning curve and learn things on-the-fly, only as needed. Nix is a massive ecosystem and has so many batteries included and components (NixOS, NixPkgs, NixOps, Nix programming language, nix-shell, nix-env, nix-darwin, home-manager, …). The good news is that those components are for the most part modular, there’s no need to adopt them all in order to reap the benefits that Nix provides.

For now, I am only adopting nix-env and nix-shell, with no *.nix config files. This post covers nix-env.

For simplicity, think of nix-env as a package manager, akin to apk, pacman, brew, apt, pkg, etc.

Install a package

$ nix-env -i moreutils
installing 'moreutils-0.67'
building '/nix/store/jsp0l5ny3kx8p9lx9w9r0x159i9jjnn6-user-environment.drv'...

I see some guides using nix-env -iA but -i seems to suffice. We could optionally specify the nixpkgs. prefix:

$ nix-env -i nixpkgs.moreutils
error: selector 'nixpkgs.moreutils' matches no derivations

Oh no! Maybe that’s what the -A is for?

$ nix-env -iA nixpkgs.moreutils
replacing old 'moreutils-0.67'
installing 'moreutils-0.67'

Indeed! Apparently that -A thing stands for attribute. The only thing I know is that there are both nixpkgs.* and nixos.*. But I don’t care about NixOS at this point. I’ll just ignore -A from now on, for the time being.

List installed packages

$ nix-env -q
moreutils-0.67

Easy! This actually gets displayed in my less pager.

Upgrade installed packages

$ nix-env -u

Easy! At this point, I am not super confident whether that works as intended though. We will find out in a few days when there’s some update to one of my installed CLI applications. I’ve heard there’s something called nix channel to control that. Leaving it for another day though.

Update(2022-02-18): I learned that nix-env -u is akin to apt upgrade or apk upgrade. It upgrades installed packages to newer versions but only if it is aware there are newer versions. To actually refresh the repositories à la apt update or apk update, use nix-channel --update.

Note: On macOS this needs to be sudo -i nix-channel --update. See issue.

Uninstall a package

$ nix-env --uninstall moreutils
uninstalling 'moreutils-0.67'
building '/nix/store/5k8rsf4cxg4iz7cqnqirpww6r97bwnqr-user-environment.drv'...

Easy!

Search for packages

$ nix-env -qaP '.*moreutils.*'

The .* seems to be needed. It works if I omit them, but only if I write the exact package name (apparently called ‘derivation’ in Nix):

$ nix-env -qaP moreutils
nixpkgs.moreutils  moreutils-0.67

If I write the wrong package name, the following happens:

$ nix-env -qaP moreutil
error: selector 'moreutil' matches no derivations, maybe you meant:
       moreutils

It was helpful in this case, but I wouldn’t always count on that. It is a bit annoying that there’s no nix search moreutils command, but it seems that nix-env is very heavily tailored to use short flags, just like pacman in Arch Linux. I got used to pacman, hopefully I can get used to the nix-env short flags at some point.

Actually I tried it out and there is a nix search command!

$ nix search moreutils
error: experimental Nix feature 'nix-command' is disabled; use '--extra-experimental-features nix-command' to override

This isn’t very promising though. How come searching is experimental?! Anyway, I can live with the nix-env form for now.

These are the 5 basic package management operations that I needed to bootstrap my dev environment. Without putting much effort on it, my initial list of package looks like this:

$ nix-env -q
atool-0.39.0
bash-interactive-5.1-p12
coreutils-9.0
exa-0.10.1
fpp-0.9.2
fzf-0.29.0
git-2.34.1
htop-3.1.2
hugo-0.92.0
jq-1.6
less-600
moreutils-0.67
ncdu-1.16
perl5.34.0-ack-3.5.0
ranger-1.9.3
stow-2.3.1
tmux-3.2a
tree-1.8.0
vim-8.2.4186
watch-procps-3.3.16
wget-1.21.2
zoxide-0.8.0

Those were very intuitive to find, with the exception of ack and bash-interactive:

• bash is a bit odd because Nix splits it into two packages: a non-interactive version and an interactive version. I have no idea why. My ~/.bashrc wrecked havoc with the non-interactive version.
• ack is very oddly named. Really. Also: nix-env -i ack doesn’t work, but nix-env -iA nixpkgs.ack does. I suspect it will be hard to ignore -A in the future.