function triangles3_write ( file_name, triangle_num, triangle_node, ...
  node_num, node3_label )

%% TRIANGLES3_WRITE writes the pressure triangles to a file.
%
%  Discussion:
%
%    The first three rows of the array TRIANGLE_NODE(6,NODE) contain
%    exactly the nodes that make up the pressure triangles.
%
%    However, we must relabel the nodes!
%
%  Modified:
%
%    22 June 2005
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, integer TRIANGLE_NUM, the number of triangles.
%
%    Input, integer TRIANGLE_NODE(6,TRIANGLE_NUM), the nodes that make up each triangle.
%
%    Input, integer NODE_NUM, the number of nodes.
%
%    Input, integer NODE3_LABEL(NODE_NUM), contains the renumbered
%    label of order3 nodes, and -1 for nodes that are not order3 nodes.
%
  file_unit = fopen ( file_name, 'wt');

  if ( file_unit < 0 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRIANGLES3_WRITE - Warning!\n' );
    fprintf ( 1, '  Could not write the file "%s".\n', file_name );
    return;
  end

  for triangle = 1 : triangle_num

    fprintf ( file_unit, '%6d  %6d  %6d\n', ...
      node3_label ( triangle_node(1:3,triangle) ) );
  end

  fclose ( file_unit );