WASHM: bash in WASM built with brush

[mihailik]

NPM: https://www.npmjs.com/package/washm
GitHub: https://github.com/mavity/washm
BlueSky latest v0.2.7 https://bsky.app/profile/was.hm/post/3maheybhkfc2o
BlueSky post on the architecture: https://bsky.app/profile/was.hm/post/3m7zghnkxpc2c

This is a functional POC, making brush runnable anywhere node is

• Unix
• Windows
• Android even!

Maybe we one day have a shell that is portable and free of hairy dependencies and Just Works everywhere no question asked.

The architecture thread has plenty on builds, cool WASM tricks and JS bridges.

I keep iterating but I thought it's already functional enough to share.

Thanks for making brush!!

[reubeno]

Very cool! Thanks for sharing this 🙂

I've long wanted to see brush runnable in a browser for demo purposes; I'd imagine that would be doable using your architecture?

Also, any feedback for brush? From the errors in your screenshot and your BlueSky thread I'm inferring you needed to work around a number of calls / unsupported operations.

[mihailik]

Thank you!

Yes, it's very POC now. Running in browser definitely on the cards, and same sort of effort to get there: wiring the syscalls properly.

When this thing goes beyond POC in this brand new 2026, I'd love to contribute WASM-compatible tweaks back.

The errors are all coming from startup rc files, and they are the most pesky nuisance, especially how they always differ per OS. It all comes down back to implementing and fixing in the syscalls though.

[mihailik]

Little progress report:

Browser WASHM

WAS.HM

Managed to get it out in browser, really buggy but it runs the actual code.

Unit tests

This weekend got a big breakthrough: figured how to write unit test for this Frankenstein's monster. It sounds boring, but it's actually a big deal, because regressions are the plague for me here.

Rather proud how I tricked the code: basically I eval( washm.js code ) in an environment pre-cooked to have typical node.js variables and APIs in scope. That way I literally run the whole JS+WASM bundle in unit test environment and can see its actual behaviour under duress.

Builtins + Coreutils: need task-local storage

I want to employ uutils/coreutils for builtins in brush, and bundle the whole thing in one WASM file.

The big deal with that is assigning the running in-process ls command its own stdio, environment and all that. A command might reach to print to stdout somewhere deep in the call graph, and I don't want to patch every function on its way to pass dedicated stdio context. Hence the need for pseudo-statics like thread-local storage. But WASM is single-threaded, so it's task-local.

If I get it working, I'll start slinging all the normal busybox-like tools in, and slap unit tests on each of them.

[oech3]

I want to employ uutils/coreutils for builtins in brush, and bundle the whole thing in one WASM file.

cksum and basenc are published currently.
uutils/coreutils#10928