Shell Compatibility Reports from Oils -- ~1300 passing

[andychu]

Hello!

I learned of this project from the README to Brush - https://github.com/reubeno/brush/blob/main/README.md

And I learned about Brush very recently, in this thread - https://news.ycombinator.com/item?id=43908368

I'm the author of https://oils.pub, which I thought was the only project tackling bash compatibility! :-) (other than toybox, which I contributed to a bit back in 2016)

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I think it's impressive how far brush and sush have gotten, although I also think there is a BIG duplication of effort!

So I made these reports to assess that, based on our spec tests:

https://pages.oils.pub/spec-compat/2025-06-19/renamed-tmp/spec/compat/TOP.html

I always intended OSH as an "executable spec" or "language definition", for other people to build interactive experiences on top of, e.g. GUIs, or something better than GNU readline:

https://www.oilshell.org/blog/2023/12/screencasts.html#headless-protocol-oils-web_shell

So it would be nice to collaborate in some way, and reduce the duplication of effort.

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I talked to the author of Brush - reubeno/brush#563

And one idea is to share some tests ... I was even thinking we can make some kind of "Bashix" spec that is bigger than POSIX. You can see in the reports that many shells now agree on bash behavior, which is not in POSIX

This way users have a more stable language to target! One reason I started the project is because I thought bash was poorly documented and implemented, e.g. if you compare to say CPython, which is a codebase of the same age

(in particular there was confusion of empty arrays and unset arrays, etc.)

[LinuxBoy-96]

Which shell is better at this point?

[ryuichiueda]

Thank you very much for your suggestion. I am now very busy with my day job right now, but I will respond when I have time!

[LinuxBoy-96]

@ryuichiueda @andychu

I'm by no means an expert, but I have strengths, weaknesses, and a unique perspective. See PRs #146 and #147, and issue #148.
So I believe I can be helpful.

The only goal I want to emphasize is making Sushi at the very least 100% POSIX compliant — and maybe even going beyond that.

We don’t need to create yet another non-POSIX shell like Fish or Ion (the one written in Rust).

At some point, I’d like to see Sushi become a fully viable shell option for any system.

[andychu]

I created the "Bashix" repo here for shell authors to collaborate on the semantics: https://github.com/bashix-spec/bashix

It's not just bash, but even POSIX shell has some questions. Which one of these behaviors matches POSIX?

I have a few other examples of 4 shells having 4 different behaviors ... it may be possible to find 5!

https://github.com/bashix-spec/bashix/blob/main/yahtzee/4-command.sh

$ ./4-command.sh 
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bash

echo
for
status=0
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dash

echo
status=0
---
mksh

echo
status=1
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zsh

echo
for
status=1