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Comment by ekidd | Hacker News Reader

> In PowerShell, structured output is the default and it seems to work very well.

PowerShell goes a step beyond JSON, by supporting actual mutable objects. So instead of just passing through structured data, you effectively pass around opaque objects that allow you to go back to earlier pipeline stages, and invoke methods, if I understand correctly: https://learn.microsoft.com/en-us/powershell/module/microsof....

I'm rather fond of wrappers like jc and libxo, and experimental shells like https://www.nushell.sh/. These still focus on passing data, not objects with executable methods. On some level, I find this comfortable: Structured data still feels pretty Unix-like, if that makes sense? If I want actual objects, then it's probably time to fire up Python or Ruby.

Knowing when to switch from a shell script to a full-fledged programming language is important, even if your shell is basically awesome and has good programming features.

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PowerShell is basically an interactive C# shell with language ergonomics targeting actual shell usage instead of "you can use it as a shell" the way Python, Ruby, etc. approach their interactive shells. However, the language and built-in utilities work best when you are passing around data as opposed to using PowerShell as if you were writing C#.

It's true, you are indeed passing around full-blown .NET runtime objects. In fact your whole shell is running inside an instance of the .NET runtime, including the ability to dynamically load .NET DLL's and even directly invoke native API's.

It feels a bit like JS in the sense that you're best off sticking to "the good parts", where you get the power of structured input/output but you don't end up trying to, for example, implement high performance async code, even though you technically could.

Are executable methods really that bad? I mean, they're bad in some abstract sense but that seems more like an objection if we were talking about a "safe" language like Rust than talking about shell scripting. For a shell executable methods seem fine. If you don't make the method executable people are just going to use eval() anyway, might as well do the more predictable thing.

It might be possible to design a good Unix shell based on objects, with the ability to "call back into" programs. But I haven't seen one yet that I'd prefer over Ruby or Python.

I do think objects make plenty of sense in languages like AppleScript, which essentially allowed users to script running GUI applications. And similarly, Powershell's objects might be right for Windows.

But nushell shows how far you can push "dumb" structured data. And it still feels "Unix-like", or at least "alternate universe Unix-like."

The other reason I'm suspicious of objects in shells is that shell pilelines are technically async coroutines operating over streams! That's already much further into the world of Haskell or async Rust than many people realize. And so allowing "downstream" portions of a pipeline to call back into "upstream" running programs and to randomly change things introduces all kinds of potential async bugs.

If you're going to have a async coroutines operating on streams, then having immutable data is often a good choice. Traditional Unix shells do exactly this. Nushell does it, too, but it replaces plain text with structured data.

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