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From: rmg@mips.UUCP
Newsgroups: comp.unix.wizards
Subject: termcap "sg#0" capability
Message-ID: <847@quacky.UUCP>
Date: Wed, 28-Oct-87 12:06:15 EST
Article-I.D.: quacky.847
Posted: Wed Oct 28 12:06:15 1987
Date-Received: Sat, 31-Oct-87 09:27:51 EST
Lines: 33
Keywords: magic cookies

I have a question about the semantics of the "sg" terminal capability.

The BSD 4.3 termcap(5) manual page describes "sg" thus:

       ...
>      sg    num          Number of garbage chars left by so or se (default 0)
       ...
>      The sequences to enter and
>      exit standout mode are given as so and se, respectively.  If
>      the code to change into or out of standout mode leaves one
>      or even two blank spaces or garbage characters on the
>      screen, as the TVI 912 and Teleray 1061 do, then sg should
>      be given to tell how many characters are left.

Notice that the manual page specifies a default of 0 for the sg
attribute.  I initially interpreted this to mean that a terminal
description with an explicit sg#0 should be equivalent to one with no
sg capability given.

However, I have a termcap driven program which behaves differently
when sg#0 is specified than when no sg capability is given. The
developer asserts that there *is* a semantic difference between sg#0
and no sg.  Since sg is the number of "blank spaces or garbage
characters on the screen", I can't imagine what the difference is.  I
haven't worked with terminals that do this, so maybe I don't
understand what these "magic cookies" do for the terminal. Can
somebody enlighten me?

-- 
- Rich Geiger
{ames,decwrl,pyramid}!mips!rmg		
MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086
(408) 720-1700 x308 [Day Job]  (408) 739-7911 [home]