Re: [O] accessing source block header arguments from exporters

[Charles Berry]

Robert Klein <roklein <at> roklein.de> writes:

> 
> Hi,
> 
> is there a way, to read header arguments to source blocks in the
> exporters org-<exporter>-src-block funktions?

Not directly. org-babel-exp-code has no provision for headers. 
They get dropped.

>
> E.g. is there a way to access :firstline in the example below?
> 

Not exactly, but ...

If you precede the code block with

#+attr_firstline: 23 

then with point in the src block

(org-element-property :attr_firstline (org-element-context))

will return ("23"). And org-*-src-block functions can use it.

If you really want to use the :firstline idiom, you can add a hook in 
`org-export-before-processing-hook' to find :firstline headers and 
insert #+attr_firstline lines in the buffer copy that the exporter is using.

> #+begin_src c++ -n :firstline 23
>    static struct
>   {
>       char                        *entity;
>       unsigned char       equiv;
>   } entities[] =
>     {
>       { "lt",           '<' } ,
>       { "gt",           '>' } ,
>       { "amp",          '&' } ,
>       { "quot",         '"' } ,
>       { "trade",        153 } , /* trade mark */
> #+end_src
> 
> I didn't find it in the `element' structure.
> 
> However, if I use
> 
> #+begin_src c++ firstline=23
>   // random C++
> #+end_src
> 
> I could access :parameters from `element' and parse the string.
> However I'm not sure if I'd break some babel stuff or not.
>

C-c C-v C-i on that src block shows that 'firstline=23' is treated as 
a switch by babel. So if there is any language that tries to use that 
as a switch (or has a regexp that matches it), there could be trouble.  
 
But in C it looks innocuous.

> If I'm trying to implement a firstline feature -- source blocks with
> new line numbering (-n) beginning at a given line number -- I'd prefer
> to use :firstline, but I didn't find anything to suggest `:XXX ZZ'
> header arguments to source blocks are available to the exporters.
> 

HTH,

Chuck