Will's blog


Seen on HN: Invert shell and terminal

31 Mar 2021

Here’s a comment from Ericson2314 that I agree with wholeheartedly:

Invert the shell and terminal: every shell command (with unredirected streams) gets it’s own pty.

Read the whole comment for more.

I think this could work well - but unlike many projects intended to improve the terminal/shell experience it could be implemented in a backward compatible way - and as such have a chance of being widely adopted.

You’d need to implement a new protocol between terminal and shell. Maybe the shell would be in charge - allocating PTYs and multiplexing the output back to the terminal. Or maybe the terminal would be in charge where it would allocate PTYs for children and send them to the shell using FD passing. There are advantages both ways.

Integral to its success though would be getting the support for this new protocol upstream in bash. Bash is the most widely deployed shell and the only way to get to the point where you can log in to a new machine (or over SSH) and expect this to “just work”. Without that it would remain a niche and could join the graveyard of other improved shells/terminals that approximately no-one uses.

As such the protocol would have to be minimal and easily implementable in C. Systemd’s protocols could be an inspiration. I’ve implemented both sides of sd_notify and LISTEN_FDS before, in more than one programming language and it was very straightforward.