Path: utzoo!utgpu!watmath!att!pacbell!ames!bionet!csd4.milw.wisc.edu!cs.utexas.edu!uunet!auspex!guy
From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.unix.questions
Subject: Re: Where Goeth the Line-editing? (was Re: Strangeness in shell)
Message-ID: <2340@auspex.auspex.com>
Date: 7 Aug 89 17:46:02 GMT
References: <13303@bloom-beacon.MIT.EDU> <795@dms.UUCP>
Reply-To: guy@auspex.auspex.com (Guy Harris)
Organization: Auspex Systems, Santa Clara
Lines: 18


 >>   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"?).