RE: [Groff] soelim and file names defined in string registers

[Ted Harding]

On 18-Aug-06 Joerg van den Hoff wrote:
> hi,
> looking at the docs and the archives I did'nt find this:
> if there are preprocessor directives in a sourced file and
> the file name is specified  in a string register in the
> document errors result.
> 
> say I have to files `t2' and `t3' which are to be sourced
> from within this document `t1':
> 
> ==============
> .ds fname t3
> .so t2
> .LP
> .so \*[fname]
> ==============
> 
> difference is that `t3' is specified in a string register.
> running `soelim' on this yields in the example (t2, t3
> containing some pic stuff):
> ===================================
> .lf 1 ./t1
> .ds fname t3
> .lf 1 ./t2
> sourced file's name specified as text.
> .PS
> boxwid = 0.5
> box
> down
> box
> .PE
> 
> 
> .lf 3 ./t1
> .LP
> .so \*[fname]
> =========================================
> 
> i.e. `t2' is already included, but the second `.so' is not yet 
> expanded(or what???). formatting this (or the orignal `t1')
> with something like
> 
> groff -s -ms -p -X t1
> 
> generates the error:
> 
> t3:2: macro error: bad arguments to PS (not preprocessed with pic?).
> 
> without preprocessor stuff in the sourced files, everything seems
> to work (ms macros do no harm, for instance).
> 
> could someone, please, explain what exactly the problem is
> (or tell me to RTFM on page xxx...)? even better would be a
> solution/work around how to specify file names of sourced files
> via variables/string registers from within the document
> (the -I option is not what I'm looking for)
> 
> many thanks
> 
> joerg

Surely, Joerg, the problem is that the file t3 is not seen until
the 'troff' component of the chain is started, since it is troff
that executes ".so". Therefore, since the preprocessor'pic' has
been run before 'troff' starts, 'pic' has not processed the
contents of file t3. This would apply to any file with preprocessor
material in it (e.g. 'eqn').

There is only one work-round that I know for the situation where
you want to bring in a file in the middle of a troff document,
where the file contains preprocessor material.

This involves using ".sy" to cause the system to run the preprocessor
on the file, storing its output into a temporary file, and then
using ".so" to read in the contents of the temporary file.

This would be on the lines of

.sy pic t3 > t3.temp
.so t3.temp
.sy rm t2.temp


So, if you already have the name "t3" defined as the string fname,
the equivalent would be

.sy pic \*[fname] > \*[fname].temp
.so \*[fname].temp
.sy rm \*[fname].temp

which should work.

NB You must be running groff in "unsafe" mode for this, since
"safe" mode suppresses most commands (including ".sy") for
something to be done by the system.

Hoping this helps,
Ted.

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Date: 18-Aug-06                                       Time: 12:36:23
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