`command return` and `\return` can't suppress function/alias lookup and certain special properties in OSH, because `return` is a keyword

[9ao9ai9ar]

So I played around with command -V in OSH and noticed that among the special built-in utilities, break, continue, exit and return are actually shell keywords. This means that the following code won't work:

command return
\exit # Unless a function named `exit` is defined, but then it won't be right.

command without options can suppress alias substitution, shell function lookup, as well as special properties of the special built-in utilities (though this last functionality is not respected in some shells): https://pubs.opengroup.org/onlinepubs/9799919799/utilities/command.html.

exit may be aliased (even in OSH, though I don't think it's possible to invoke the alias instead of the keyword), but neither methods of suppressing alias substitution can be used on it.

Do you plan to implement this "quirk and bug" of bash and other POSIX-compatible shells?

[andychu]

Thanks for trying it

That is a known difference - https://oils.pub/release/latest/doc/known-differences.html#break-continue-return-are-keywords-not-builtins

We are "conceding to reality" on some of these differences, but it's prioritized by running real shell scripts

If you have an example of a real shell script it breaks, that will take priority

If it's a synthetic case, then it's lower priority

Right now the top issue is that our IFS algorithm needs to be rewritten, since that blocks some real shell scripts

---

There are some threads on Zulip about this too

https://oilshell.zulipchat.com/#narrow/channel/384942-language-design/topic/Fundamental.20reasons.20for.20OSH.20incompatibility

[9ao9ai9ar]

I should have read the docs before posting - thanks for linking to it.

It's just used in my personal shell scripts, so nothing like a high profile real world use case.

I didn't know about the IFS incompatibilities - that would definitely also break my scripts.

[andychu]

No problem, it's useful to know that people ran into this in their own scripts!

Examples can help

Sometimes people test synthetic cases, which is also welcome, but it is lower priority

[9ao9ai9ar]

The script I used, which is the same as the one in #2224, is now published in the linked pull request above. The less mainstream use of shell commands that encountered this issue can be seen in the init function and the initial block of code above it and download_file.

[andychu]

OK yeah I can see that other people may use this idioms to suppress alias and function lookup

And there is probably a way to implement it in OSH which is not too hard ... we could make command exit and \exit work, I think

[akinomyoga]

If you have an example of a real shell script it breaks, that will take priority

• This is ble.sh 49. I reported this on 2024-06-29 https://oilshell.zulipchat.com/#narrow/stream/121540-oil-discuss/topic/.5Creturn.200.20doesn't.20work for the real cases in ble.sh.
• builtin return has the same issue, and builtin return is used by kitty's shell integration.
  • Ghostty shell integration also uses builtin return.
  • VS Code shell integration also uses builtin return.