Hi Jeff,
> A traditional idiom for doing this was calling ‘so’ with the no-break
> control character, e.g.,
>
> 'so /usr/lib/tmac/tmac.m
>
> This probably wouldn’t be the preferred way of doing things anymore
I see no reason to demote it. :-)
soelim(1) from heirloom-doctools says
Note that inclusion can be suppressed by using ‘'’ instead of ‘.’,
i.e.
'so /usr/ucblib/doctools/tmac/s
> I can’t find any mention of this in the groff documentation.
I think groff's info has empty sections for `gsoelim'.
File: groff.info, Node: gsoelim, ...
6.8 'gsoelim'
=============
* Menu:
* Invoking gsoelim::
File: groff.info, Node: Invoking gsoelim, Prev: gsoelim, Up: gsoelim
6.8.1 Invoking 'gsoelim'
------------------------
> The careful reader of the groff soelim man page will see that the same
> thing can be accomplished by putting whitespace between the standard
> control character and the request (e.g., “. so”)
But doesn't suggest why that's useful.
Whilst looking at this, I noticed groff's info says
-- Request: .so file
...
Since 'gtroff' replaces the 'so' request with the contents of
'file', it makes a difference whether the data is terminated with
a newline or not: Assuming that file 'xxx' contains the word
'foo' without a final newline, this
This is
.so xxx
bar
yields 'This is foobar'.
A Unix (POSIX) text file is zero or more lines, each terminated by ASCII
LF. If a non-empty file doesn't end with LF then it's not a text file,
and traditionally various Unix programs would silently ignore that
trailing noise so it was a bad idea to import foreign programs that
created such corruption. ;-) Should groff's documentation be
encouraging such practice? Does it work?
$ cat nontext
This is
.so emacs.bin
bar.
$ od -c emacs.bin
0000000 f o o
0000003
$ groff -Tascii -s nontext | sed '/^$/q'
This is foo bar.
$
$ soelim nontext
.lf 1 ./nontext
This is
.lf 1 ./emacs.bin
foo
.lf 3 ./nontext
bar.
$
OK, the LF is being added to separate the `lf' request. Turn those off.
$ soelim -r nontext
This is
foo
bar.
$
soelim must still add it. It's not in the input.
$ LC_ALL=C strace -e trace=read soelim -r nontext
...
read(3, "This is\n.so emacs.bin\nbar.\n", 4096) = 27
This is
read(4, "foo", 4096) = 3
read(4, "", 4096) = 0
foo
bar.
read(3, "", 4096) = 0
And can't that effect be portably obtained with `\c'?
$ cat text
This is
.so continued
bar.
$ sed -n l continued
foo\\c$
$ groff -Tascii -s text | sed '/^$/q'
This is foobar.
$
I think groff's documentation should acknowledge an old technique, say
it was never a good idea, that it doesn't work with groff, and that `\c'
can achieve the desired result.
Heirloom does handle it.
$ /usr/heirloom/bin/ucb/soelim nontext
This is
foobar.
$
--
Cheers, Ralph.
https://plus.google.com/+RalphCorderoy
