Plan 9 from Bell Labs

First of all: Plan 9 is not another flavor of nix. If you expect it to be like Unix, you will* have a bad time.

With that said:

* All services are network-enabled file servers speaking a common protocol called 9P.

* UI makes heavy use of mouse chording, is inspired by Oberon and old school Smalltalk environments. Supports seamless interaction through an inter-application messaging mechanism called plumber (e.g. you can write a rule that will make all ISBN numbers in a desktop application automatically act as a hyperlink to a web application).

* The rc shell fixes a lot of deficiencies in the Bourne shell.

* Per-process namespaces obsolete a whole lot of things like symlinks.

* There is no superuser (root account). This is obsoleted by an auth server called Factotum.

* Uses its own compiler suite that makes cross-compilation particularly easy, compared to the mess of doing so with GCC. It also uses its own much cleaner libc routines that are quite distinct from POSIX or the messy glibc additions of today. Has its own thread library, as well.

* All network information is held in a text file database mounted on a file server.

* The default file system (Venti) is inherently versioned, introspectable and has backup built into it. You can do things like swap in libraries from cache and revert changes without a hitch.

* Everything is statically linked.

* Uses mk instead of make.

* A lot of things like recursive copy and find aren't built into the standard commands. It's expected you actually chain together commands instead of reinventing the wheel for every single operation. The canonical example is the use of du to walk the file system tree, for everything. This replaces find and other things.

* Designed not just to be multi-user, but multi-tenant. Makes many uses for containers and access controls unneeded because of its core design.

* So much more.

Try it. It's more relevant now than ever.

While we could keep playing language-of-the-week-golf -- the go compiler is born from the plan9 c-compiler, and the go designer(s) had a hand in designing plan9. So my comment wasn't quite meant as just a popular-language-x-quip. Plan9 reborn in gopher clothing actually has some merit.

(Not that plan9 in rust wouldn't have merit -- I wonder, post Rust 1.0, if someone ends up writing a full OS, starting with Rust and as much assembler as needed -- if it would make sense to mix go and rust for some of the user-space -- or if it'd make more sense to just stick with Rust).

Troll(1) works without even running it

OS/2 Presentation Manager and SOM tried it.

Oberon also had quite nice concepts, specially version 3 with Gadgets.

> Acme is amazing, but the whole thing uses mouse chording and requires a 3-button mouse, so it requires a lot of getting used to if you're newer to computers than, say, 1990.

That is based on how Oberon UI works, which then again is based on Mesa/Cedar at Xerox PARC.