stdio/fileno.c

   1 /* Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <errno.h>
  20 #include <stdio.h>
  21
  22 /* Return the system file descriptor associated with STREAM.  */
  23 int
  24 fileno (stream)
  25      FILE *stream;
  26 {
  27   extern void __stdio_check_funcs __P ((FILE *));
  28
  29   if (! __validfp (stream))
  30     {
  31       __set_errno (EINVAL);
  32       return -1;
  33     }
  34
  35   __stdio_check_funcs (stream);
  36
  37   if (stream->__io_funcs.__fileno == NULL)
  38     {
  39 #ifdef EOPNOTSUPP
  40       __set_errno (EOPNOTSUPP);
  41 #else
  42       __set_errno (ENOSYS);
  43 #endif
  44       return -1;
  45     }
  46
  47   return (*stream->__io_funcs.__fileno) (stream->__cookie);
  48 }