[TUHS] getting nroff to underline in v6,v5
random832 at fastmail.com
Mon Sep 28 04:12:14 AEST 2015
Mark Longridge <cubexyz at gmail.com> writes:
> It seems that nroff had the ability to show underlined text very early
> on, possibly as early as v3 according to the v3 manual.
> I haven't managed to get this to work right under simh but I was
> thinking maybe there's a way to do it. It needs an 'underline font'
> but the mechanism of how this worked in the old days is a bit of
> mystery to me. The output device would have to have the ability to
> either display or print underlined text. Maybe someone can remember
> which terminal devices supported this in the old days which worked
> "out of the box" in the v5,v6 era.
> Maybe there was the ability to use overstrike characters on the teletype?
> In bash I can use:
> echo -e "\e[4munderline\e[0m"
The proper escape sequence to end underline is technically \e[24m; using
0 here ends all other formats (bold, color) as well.
> Shouldn't be too hard to hack up something that works in emulated v5.
The "ul" utility, which converts from overstrikes to termcap-based
escape sequences, first appeared in 3.0BSD.
The source code is here:
It'd probably be pretty easy to rip out the termcap dependency and have
it just output ansi codes, though I don't know what dialect of C works
1BSD to 3BSD also had an "iul" utility which just printed a row of
dashes under characters to be underlined instead of using escape
sequences. In 2.9BSD and 4BSD and later this functionality is provided
by "ul -i".
It looks like this wouldn't be hard to modify to use escape sequences
instead, and it uses the oldest C dialect of any of these versions.
>From 4.1c BSD, ul also handles bold, which is represented by
self-overstriking in the nroff output, and represents superscript and
subscript (half-linefeed) with dim attributes. Any missing attributes
are represented with standout. This is essentially the same
functionality available in modern versions of ul.
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