How to use gnuplot from an Ada program?

General
1

Sometimes I want to use external tools like gnuplot or castle-model-viewer straight from my Ada code. Does anyone know a good way to do that?

2

If I understand you correctly (and I may not) it’s similar to when I once wanted to use glpk from Ada. In that case I generated a thin binding.

3

The naive way is to make data files for a gnuplot script or to print out a gnuplot script which the Ada program starts using a procedure “to_os”:

   procedure to_os (str : string) is
      package c renames interfaces.c;
      procedure system_rk (source : in c.char_array);
      pragma import (c, system_rk, "system");
   begin
      system_rk (interfaces.c.to_c (str));
   end to_os;

But I would like (at least) to pipe data into a gnuplot script.

4

This is what I did: https://github.com/pmunts/libsimpleio/blob/f5354ded9aae84452e4b1cb64f3dd52902ac97c2/ada/programs/test_gnuplot.adb

It’s pretty straightforward. External_Command.Pipeline is my wrapper package around popen() and friends. You could also just call popen(), fputs(), and pclose() directly without any wrapper package.

5

I may ask too impulsively, but where is "“external_command.ads”? I get file “external_command.ads” not found when trying to compile “test_gnuplot.adb”.

6

I use Util - The Ada 95 Utility Library

The pipe section

can be downloaded from

And the use as pmunts test program, i.e with open/put_line/close

7

Sorry for the omission. It is part of my Linux Simple I/O Library. If you use Alire, just alr with libsimpleio to pick it up.