How to simulate a TTY while also piping stdio?

Question

I'm looking for a cross-platform solution for simulating a TTY (PTY?) in Rust while also piping stdio.

The frontend is based on web technologies where an interactive terminal is shown. Users can run commands and all their inputs will be sent to the Rust backend, where the commands get executed. Std{in,out,err} are sent back end forth to allow for an interactive experience.

Here's a simplified example (piping only stdout):

let mut child = Command::new(command)
    .stdout(Stdio::piped())
    .spawn()
    .expect("Command failed to start");

loop {
    let read = reader.read(&mut chunk);

    if let Ok(len) = read {
        if len == 0 {
            break;
        }
        let chunk = &chunk[..len];

        send_chunk(chunk); // send chunk to frontend
    } else {
        eprintln!("Err: {}", read.unwrap_err());
    }
}

Currently, running the command tty prints: not a tty, but ideally, it should output a file name (e.g /dev/ttys002). And programs, such as atty should return true.

Running only the backend in a terminal, with stdio inherited works, but then I can't send the stdio back to the frontend.

Answer 1

Define "cross platform". As far as PTYs is concerned, those are pseudo devices supported by the kernel, complete with ioctls and everything. As a matter of fact a lot of the things your terminal emulator will have to do, is implementing the receiving end of those ioctls.

As long as you're on a machine with the BSD API (which includes Linux), the best course of action would be to openpty and roll with that. If you want to be portable to non BSD PTY capable systems, you'll have to hook the tty functions in the child process (by preloading a helper library).