Close a file designated by a Fortran-style integer logical unit.

   None.

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   unit       I   Fortran-style logical unit.

   unit           is an integer representing a Fortran logical unit.

                  Fortran logical units are integers which in the
                  Fortran language play a role analogous to pointers to
                  FILE structures in C.  In Fortran, when a file is
                  opened and a logical unit is associated with the
                  file, the file and unit are said to be ``connected.''
                  A logical unit, once connected to a file, may be used
                  to refer to the file in Fortran I/O statements.

   None.

   None.

   This function is provided in order to fully support the file I/O
   interface provided by those CSPICE functions generated by running f2c 
   on Fortran SPICELIB routines.  ftncls_c should be used to close files 
   opened by these functions ONLY IF the files in question would 
   normally be closed, after having been opened by a Fortran program,
   by a Fortran CLOSE statement.  If a file has been opened by a 
   function that has a corresponding "close file" function, the latter
   should be used to close a file.  Examples are the DAF and DAS 
   families of functions:  DAFs are normally closed via dafcls_ and
   DAS files are normally closed via dascls_. 

   1) Extract comments from a DAF-based kernel---an SPK file for 
      example---into a text file.

         #include <string.h>
         #include "SpiceUsr.h"
              .
              .
              .

         #define   SPK      "my.bsp"
         #define   OUTFILE  "my.txt"

         SpiceInt           handle;
         SpiceInt           unit;

         /. 
         Open a new text file for write access, obtaining a Fortran 
         logical unit.
         ./

         txtopn_  ( OUTFILE, &unit, strlen(OUTFILE) );

         /.
         Open the SPK file from which comments are to be extracted.
         ./
         dafopr_  ( SPK, &handle, strlen(SPK) );

         /.
         Extract comments into the text file.
         ./
         spcec_   ( &handle, &unit );

         /.
         Close the text file.
         ./
         ftncls_c ( unit );

   1) 

   Error free.

   The file connnected to unit would normally have been opened via a 
   call to a function generated by running f2c on a Fortran SPICELIB
   routine.  Examples of such functions are

     txtopn_
     txtopr_

   W.L. Taber      (JPL)
   I.M. Underwood  (JPL)
   E.D. Wright     (JPL)

   1) Refer to the SPK required reading file for a complete list of
      the NAIF integer ID codes for bodies.

   -CSPICE Version 1.0.0, 24-MAY-1999 (NJB)

   close file designated by Fortran logical unit