Date: Tue, 25 Mar 1997 14:56:27 +0000 From: Brian Somers <brian@shift.lan.awfulhak.org> To: freebsd-hackers@freebsd.org Cc: Andrew Gierth <andrew@erlenstar.demon.co.uk> Subject: Re: Backspace = ^H Message-ID: <199703251456.OAA00459@shift.lan.awfulhak.org>
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I thought this might contribute to the discussion:
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Newsgroups: comp.unix.bsd.freebsd.misc
Cc: brian@awfulhak.demon.co.uk, brian@utell.co.uk
Subject: Re: Backspace = ^H
References: <5h2c01$4i2@reader.seed.net.tw> <5h6e83$1mk@ui-gate.utell.co.uk>
<E7KvDC.ILE@nemesis.lonestar.org> <5h8905$lj1@ui-gate.utell.co.uk>
From: Andrew Gierth <andrew@erlenstar.demon.co.uk>
Organization: disorganised
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Date: 25 Mar 1997 13:43:14 +0000
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In-Reply-To: brian@shift.lan.awfulhak.org's message of 25 Mar 1997 10:21:57 GMT
Posted-To: comp.unix.bsd.freebsd.misc
The following message is a courtesy copy of an article
that has been posted as well.
>>>>> "Brian" == Brian Somers <brian@shift.lan.awfulhak.org> writes:
Brian> I think we should have no stty in any .profile, and either of the
Brian> following:
Brian> * The Backspace key sending ^? and a default stty erase char of ^?
Brian> * The Backspace key sending ^h and a default stty erase char of ^h
Brian> The DEL key would send whatever the Backspace key doesn't.
Brian> (I'd prefer BS=^?, DEL=^h)
DEL=^h ?? You have *got* to be kidding.
This whole debate (which gets thrashed out regularly in comp.emacs) always
originates from a confusion between destructive and non-destructive
backspaces. The ASCII BS character (0x08) is, from the point of view of an
output device, an instruction to move back one position, non-destructively.
The ASCII DEL (0x7f) is an artifact of paper tape; a character can be erased
from a tape by punching all the holes out, leaving a DEL, which is then
ignored. (A vestige of this remains in some systems where DEL can be used
for padding instead of NUL.) It's no more correct to use ^h as a destructive
backspace than any other control character, whereas DEL has always been
associated with the concept of "delete last input character".
>From a user's point of view, and assuming a PC keyboard, there are two keys
to consider; the <- (backspace) key, and the "Delete" key. Normal user
expectations require <- to behave as a *destructive* backspace, and "Delete"
to be 'delete character forward' (kdch1 in terminfo-speek). This can best be
achieved by having <- generate DEL, having "Delete" generate an escape
sequence, and defaulting to 'stty erase ^?'. (Which is what I have done on
my system, and have done in the past to many other Unix flavours, terminals
and terminal emulators.) This leaves ^h free, which keeps Emacs happy.
Having "Delete" generate ^h is insane, and likely to confuse people
considerably.
- --
Andrew.
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