Where Goeth the Line-editing? (was Re: Strangeness in shell)

[Guy Harris]

 >>   In multics, it was possible to install a driver that lived at the
 >> gateway between the actual terminal and user processes.  This driver
 >> would intercept and process *all* input before sending it to the
 >> process.
 >
 >Actually, Un*x has this "feature" as well. At least, sort of.

Except that the Multics driver could live in user mode, and be inserted
into the I/O stream by J. Random User without getting the help of a
system administrator; UNIX line disciplines and streams modules tend to
live in the kernel, which means that, in general, 1) they require a
privileged user to install them and 2) their pages are wired down.

With a reasonable pseudo-tty-like mechanism, you can run the input line
editor as a separate process, buying back the advantages of the Multics
one (you can even do much of it without as wonderful a pseudo-tty
mechanism as you'd like - can you say "EMACS shell window"?).