NAME
          isopen - Determines whether output file is open

     SYNOPSIS
          #include "lpj.h"

          Bool isopen(const Outputfile *output,int index);


     DESCRIPTION
          Function determines whether output data file has been
          successfully opened.  The arguments of isopen are:

          output
               Pointer to initialized output data. output must be
               initialized by fopenoutput().

          index
               Index of output data file to be checked.

     RETURN VALUE
          Function returns TRUE if output for index has been opened,
          FALSE otherwise.


     AUTHORS
          For authors and contributors see AUTHORS file


     COPYRIGHT
          (C) Potsdam Institute for Climate Impact Research (PIK), see
          COPYRIGHT file


     SEE ALSO
          fopenoutput(3), fcloseoutput(3)