Julia EvansApr 21, 2025

terminology poll: what would you call the part of the operating system that is responsible for managing the pseudoterminal device? (handling ioctls, tracking the foreground process, remembering the terminal window size, turning `Ctrl+C` into a SIGTERM, handling `Ctrl+S` and `Ctrl+W`, etc)

(also open to hearing that you think that it's not just one thing or anything else really)

line discipline
4.7%
terminal driver
51.4%
what?
39.6%
other
4.2%
Poll ended at .
Show threadGarrett WollmanApr 21, 2025
@b0rk Some of those things are part of the line discipline, but not all of them, and the distinction is largely confusing and unnecessary today. But they're not part of a "driver" per se, they're part of the kernel's terminal abstraction (and in particular they're part of common code that is shared between both the pty "driver" and the drivers for hardware terminals like the UEFI console and serial ports). You could say maybe "tty layer" and not get too many complaints.
Show threadJulia Evans
@wollman what do you mean that they're not part of a “driver”? as far I can tell in Linux most of the code for this stuff is in `drivers/tty`, is the stuff In drivers/tty not a “driver”?
Apr 21, 2025 at 7:12pmWeb
Show threadGarrett WollmanApr 21, 2025

@b0rk I can't speak for the organization of the Linux kernel's source code; I'm not a Linux kernel developer. In Unix, it was in `sys/tty.c`, which has a comment at the front:

/*
* general TTY subroutines
*/

i.e., it's a library of functions to implement the things required by TTY drivers. As more functions have been added over time, functions have been split out into other source files (there are 7 sys/tty*.c files by 4.3BSD in 1986) but it's always been core device-independent kernel code.

Show threadJulia EvansApr 21, 2025
@wollman what do you mean by "Unix”? i never know what people mean when they say that, I always think of Unix as meaning "any POSIX system” but I guess that's not what you mean
Show threadGarrett WollmanApr 21, 2025
@b0rk I mean "The Unix®️ Operating System, published by AT&T Bell Laboratories in the 1970s and later by various other AT&T business units and their licensees and successors ever since." The copyright was owned by Caldera for a brief moment, as a result of which, it is now possible to freely read and distribute the source to heritage Unix releases like Seventh Edition and 4.2BSD. (The trademark now belongs to The Open Group and can be licensed even by non-AT&T-derived implementations.)