update-alternatives is a utility to manage executable symlinks in /usr/local/bin. It implements a subset of the functionality in Debian's tool of the same name. Information about alternatives is stored in /etc/alternatives for recovery between invocations of update-alternatives.

$ sudo update-alternatives add $(which gcc) cc 10
using /usr/bin/gcc for cc with priority 10
$ sudo update-alternatives add $(which clang) cc 20
found link cc with 1 alternatives
added alternative /usr/bin/clang with priority 20
using /usr/bin/clang for cc with priority 20
$ update-alternatives list cc
found link cc with 2 alternatives
alternatives for cc:
    /usr/bin/gcc: 10
    /usr/bin/clang: 20
$ update-alternatives remove $(which gcc) cc
found link cc with 2 alternatives
removed alternative /usr/bin/gcc
using /usr/bin/clang for cc with priority 20
$ update-alternatives list cc
found link cc with 1 alternatives
alternatives for cc:
    /usr/bin/clang: 20

The first invocation of update-alternatives will require read-write access to the directory /etc/alternatives should the directory not exist already.

update-alternatives list NAME will list all currently installed alternatives for the link NAME and their priority.

update-alternatives add TARGET NAME PRIORITY will add or modify the list of alternatives. There will be an alternative for NAME that points to TARGET with numeric priority PRIORITY after invocation of this subcommand. You will require read-write access to /usr/local/bin and /etc/alternatives to run this subcommand.

update-alternatives remove TARGET NAME will remove the alternative for NAME that points to TARGET should there be one. If such an alternative is not found, this is a no-op. You will require read-write access to /usr/local/bin and /etc/alternatives to run this subcommand.

update-alternatives sync will rewrite all symlinks in /usr/local/bin based on what is defined in /etc/alternatives without modifying the database. This is useful for package manager hooks.

To keep alternatives in sync automatically when packages are installed, upgraded, or removed, you can install a pacman hook that runs after each transaction. Create a file named update-alternatives.hook in either /etc/pacman.d/hooks/ (system-specific) or package it into /usr/share/libalpm/hooks/ with the following content:

[Trigger]
Operation = Install
Operation = Upgrade
Operation = Remove
Type = Path
# Re-run when these areas may change
Target = usr/bin/*
Target = usr/local/bin/*
Target = etc/alternatives/*

[Action]
Description = Rebuilding alternatives symlinks
When = PostTransaction
Exec = /usr/bin/update-alternatives sync

This hook will run update-alternatives sync as root after pacman finishes a transaction, ensuring the symlinks in /usr/local/bin match the current alternatives database.

Clone this repository, then run cargo build --release in the root of the repository. Copy the executable located in target/release/update-alternatives to your installation directory, such as /usr/local/bin.

Arch Linux (naturally) doesn't have update-alternatives, nor was I able to easily find one on AUR. This seemed fun and easy enough.

update-alternatives is authored by Gregory Meyer and now maintained by Fabian Thomys, and is licensed under the BSD 3-Clause license.