Streams line disciplines (was POSIX bashing, cooked vs raw or cbreak mode)

[Guy Harris]

>I imagine it would be possible (since the RFS file system type does
>something like it) to write a special streams module that would
>communicate with some specifiable user-level process to perform the
>user-interface functions,

At least in S5R4, a streams driver of that sort, along with some added
streams modules, already exists.

Of course, the subsystem consisting of that stuff is called the
pseudo-tty subsystem, so some members of the audience may be turned off
by it, but....

(I.e., shove some editor - EMACS, Andrew's "termulator", *urk*
"cmdtool", "atty", or whatever - in front of the pseudo-tty.)

It's unfortunate, perhaps, that "read()" and "write()" and the like are,
in most UNIX systems, treated as purely kernel functions; other systems
might do the interface to special files in *user* mode, with some
*internal* (and undocumented, and subject to change without notice)
kernel interfaces used by the user-mode interface to special files.  (As
I remember, that's precisely what Multics did; Apollo's Domain systems
may do something similar.)

You could then have your choice between an IPC-oriented scheme like
pseudo-ttys or a procedure-call oriented scheme like Multics I/O modules
(and probably have endless debates on USENET over which was better).

> but it would probably not be worth it.

Maybe, maybe not.  A tty driver of sufficient power to make me switch is
probably something I would *not* want in the kernel; it'd be *too*
powerful.  I *do*, however, missing having "ksh"-style command editing;
one of these days, I'll have to switch over to the version of the Andrew
"termulator" into which I dropped a "ksh"-style implementation of ^O, or
start using "atty" (which already has it), and see whether it does it
for me.  (I'd start using "bash" if only I could turn off its
#@@$@@!#!!@ interactive search, or incremental search, or whatever the
heck it's called.  People who like it are welcome to it.  *I* don't want
to be forced to accept it as the price of admission....)