gfs_closedir - close a directory
       #include <gfarm/gfarm.h>
       char * gfs_closedir (GFS_Dir dir);
       The gfs_closedir() function closes the directory stream associated with
       dir.  The directory stream descriptor dir is not available  after  this
       call.
       NULL   The function terminated successfully.
       Others An  error except the above occurred.  The reason is shown by its
              pointed strings.
       gfs_opendir(3), gfs_readdir(3)