posix/spawn_valid_fd.c

   1 /* File descriptor validity check for posix_spawn file actions.
   2    Copyright (C) 2000-2018 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include "spawn_int.h"
  20
  21 #include <unistd.h>
  22
  23 bool
  24 __spawn_valid_fd (int fd)
  25 {
  26   long maxfd = __sysconf (_SC_OPEN_MAX);
  27   return __glibc_likely (fd >= 0)
  28     && (__glibc_unlikely (maxfd < 0) /* No limit set.  */
  29         || __glibc_likely (fd < maxfd));
  30 }