help with too many open files

[hemphill@xxxxxxxxxxxxxxxxx (Charles Hemphill)]

After calling the write_histogram function below a couple of dozen
times, I get the message:

  ncredef: filename "hcaa8842": Too many open files

Why?  I'm believe that I'm calling ncendef and ncclose in the
appropriate places.  None of the assertions fail.  Any help would be
appreciated.

Thanks,
Charles

----------------------------------------------------------------------
static int write_histogram(char *filename, long *values, long duration_max)
{
  int ncid;
  int status;
  int dur_max_dim;
  int dimids[1], dur_hist_id;
  static long start[] = {0};    /* start writing at index 0 */
  static long count[1];

  ncid = ncopen(filename, NC_WRITE);
  assert(ncid >= 0);

  status = ncredef(ncid);
  assert(status >= 0);
  dur_max_dim = ncdimdef(ncid, "duration_max_frame", duration_max);
  assert(dur_max_dim >= 0);
  dimids[0] = dur_max_dim;
  dur_hist_id = ncvardef(ncid, "duration_histogram", NC_LONG, 1, dimids);
  status = ncendef(ncid);

  count[0] = duration_max;
  status = ncvarput(ncid, dur_hist_id, start, count, values);
  assert(status >= 0);

  status = ncclose(ncid);
  assert(status >= 0);

  return 0;
}