Nix

# Build nix package locally.
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# cd into cloned https://github.com/NixOS/nixpkgs
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# Build package from default.nix inside nixpkgs. Will put result as ./result if succeeds
# i.e. nix-build -A watchexec -> will build watchexec package
nix-build -A <package>
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# Install the build and put it `~/.nix-profile/bin`
nix-env -i ./result

# Garbage collect
sudo nix-collect-garbage --delete-older-than 30d