stdio/fileno.c

   1 /* Copyright (C) 1991, 93, 94, 96, 97, 98 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 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 }
  49
  50 weak_alias(fileno, fileno_unlocked)