[wat10000]

If you were designing a command-line interface from scratch, you'd definitely make it so that the command prompt gets displayed consistently and reliably after each command terminates, regardless of what garbage it spewed. The only reason we see anything different is because UNIX systems happened to grow that way, and everything gets crammed through an interface that was originally designed to show characters on physical paper.

With the design we actually have, the shell is the only thing in the chain that could reset the TTY state and ensure that the prompt gets displayed consistently each time, and it should. I wouldn't go so far as to say that I expect it to (my expectations for computers are not high in general) but it ought to.

[1718627440]

command-line interface != shell

Maybe that should be actually the job of the terminal emulator instead. It could happen when a new pseudo terminal is (de)allocated, which is ordered by the shell.

[wat10000]

> command-line interface != shell

I realize that. That's why I was talking about a hypothetical where it was designed all together, instead of evolving over the decades like we did.

In the situation we actually have, the shell is the only single entity that's in a position to actually do this. The terminal emulator doesn't know when a command completes. Of course, it doesn't have to be solved in a single entity. It would make sense to have the shell signal command completion to the terminal emulator, and let the terminal emulator do whatever it wishes with that information, which could include resetting any garbage state.

[1718627440]

I don't think we really disagree.

I think that even when you would design it all today the distinction between interface and running program would still be useful, otherwise every program would need to implement it's own interface and a shell does more than just communicate interactively with the computer. It's also a task runner, program orchestrator, controls program selection and allows for automating other programs.

> It would make sense to have the shell signal command completion to the terminal emulator, and let the terminal emulator do whatever it wishes with that information, which could include resetting any garbage state.

The thing is, it kinda works this way already. I'm not that knowledged about the actual interaction, but the shell already tells my terminal what the current directory is, which programs it has invoked, so that my terminal emulator can show me this in the chrome.

Ok, so my stance is: Yes it is not the job of the shell to modify the output of some program, but it is the job of the shell to tell the terminal emulator to do that, when the user requests this. I'm positively minded, that actually someone can chime in and say "ah, that's just not the default, you can configure bash, readline, etc. to do that though." I think the thing is, that bash just assumes that programs are POSIX-compliant and POSIX specifies, that every programs outputs a newline. Actually POSIX doesn't define it as newline, it defines it as the end of line. A program that forgets LF doesn't have forgotten to advance output a newline, it has output an incomplete line in that reading.