########################################################################
##
## Copyright (C) 2009-2022 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
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## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
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########################################################################

## -*- texinfo -*-
## @deftypefn {} {@var{stream} =} __gnuplot_open_stream__ (@var{npipes}, @var{h})
## Undocumented internal function.
## @end deftypefn

function plot_stream = __gnuplot_open_stream__ (npipes, h)

  [prog, args] = gnuplot_binary ();

  if (npipes > 1)
    [plot_stream(1), plot_stream(2), pid] = popen2 (prog, args{:});
    if (pid < 0)
      error ("__gnuplot_open_stream__: failed to open connection to gnuplot");
    else
      plot_stream(3) = pid;
    endif
  else
    plot_stream = popen (sprintf ("%s ", prog, args{:}), "w");
    if (plot_stream < 0)
      error ("__gnuplot_open_stream__: failed to open connection to gnuplot");
    endif
  endif

  if (nargin > 1)
    set (h, "__plot_stream__", plot_stream);
  endif

endfunction
