Re: wait_for_file ??

[John W. Eaton]

On  3-Sep-2010, Michael D Godfrey wrote:

| On 09/03/2010 05:21 AM, Ben Abbott wrote:
| 
|     The approach in 1, has a problem. I'd intended that the __wait_for_file__ 
to be used when calling fig2dev, pstoedit (whose input is eps, so that's ok), 
and when appending pages which may be ps or pdf.
|     
|     Thus, using  `drawnow("eps", filename)' won't work since the format may 
not be "eps", and we'd over-write the file we're waiting for.
| 
| OK.  So, it looks like it is necessary to find out why the *.eps write is not
| completed.

I'm coming into this a little late, so I might not understand all the
details.  Actually, I can't even seem to find the beginning of the
thread as the first message I see with the subject "wait_for_file" is
a reply to another message that I can't locate.

As I understand the current print.m, the backend-specific print
function is supposed to generate a PostScript file that, if necessary,
will be processed by ghostscript to generate the specific output file
type that is desired.  Correct?  If so, then instead of generating a
file and dealing with possible race conditions, how about doing
something like

  if (postprocess_with_gs)
    fid = popen (gs command);
  else if (send_to_printer)
    fid = popen (lpr_command);
  else if (write_to_postscript_file)
    fid = fopen (ps_file_name);
  else
    error ("???");
  endif

  feval (backend_print_function, fid, opts);

Then the backend print function will just write its output to the open
file through fid.

If that's not possible, then is there some way to create a pipeline of
shell commmands so that we don't have to worry about whether writing
to the temporary intermediate file has been completed?

Also, looking at the current gnuplot and fltk print functions, it
seems like there is some duplication of code.  I didn't expect to find
anything about ghostscript in either of those functions as I thought
the idea was to have them just generate PostScript and that
ghostscript would only be used by the calling function.

Can someone explain the design to me?

Thanks,

jwe