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From: guy@gorodish.UUCP
Newsgroups: comp.unix.questions
Subject: Re: vms vs unix
Message-ID: <19625@sun.uucp>
Date: Mon, 25-May-87 15:36:19 EDT
Article-I.D.: sun.19625
Posted: Mon May 25 15:36:19 1987
Date-Received: Tue, 26-May-87 03:01:23 EDT
References: <429@its63b.ed.ac.uk>
Sender: news@sun.uucp
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> Ummm, if it doesn't use termcap/terminfo, then presumably it makes all sorts
> of unsafe assumptions about how your terminal works - otherwise editing of
> any kind would be impossible.

Nope.  It makes only some simple assumptions, that should be true on
anything other than a truly wretched terminal.

> (Eg, it has to know how to backspace, at the very least, and to edit
> multiple lines simultaneously it would have to know how to move the
> cursor up and down). What happens if your terminal uses some character
> other than \b for backspacing (as specified by a "bc" termcap entry)?

You lose, but so what?  If ^H does something other than moving the
cursor one position to the left (e.g., something truly idiotic like
sending it home), the "crt rubout" modes provided by many UNIX tty
drivers won't work either.  The only reasonable things ^H can do are
to move the cursor one position to the left destructively or
non-destructively.

Most of the terminals in the termcap database do not have a "bc"
entry, so they presumably move the cursor one position to the left
non-destructively when they get a ^H.  It's not clear it's worth the
extra complexity to make "ksh" support the few remaining terminal.

> [Disclaimer: I've never used ksh very seriously. Perhaps its not possible to
> edit lots of lines at once - unless you start up a "real" editor]

It's not.  That's why it doesn't need to know how to move the cursor
up and down.
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com