sysdeps/posix/dup2.c

   1 /* Copyright (C) 1991-2015 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <fcntl.h>
  20 #include <limits.h>
  21 #include <unistd.h>
  22
  23 /* Duplicate FD to FD2, closing the old FD2 and making FD2 be
  24    open the same file as FD is.  Return FD2 or -1.  */
  25 int
  26 __dup2 (fd, fd2)
  27      int fd;
  28      int fd2;
  29 {
  30   int save;
  31
  32   if (fd2 < 0
  33 #ifdef OPEN_MAX
  34       || fd2 >= OPEN_MAX
  35 #endif
  36 )
  37     {
  38       __set_errno (EBADF);
  39       return -1;
  40     }
  41
  42   /* Check if FD is kosher.  */
  43   if (fcntl (fd, F_GETFL) < 0)
  44     return -1;
  45
  46   if (fd == fd2)
  47     return fd2;
  48
  49   /* This is not atomic.  */
  50
  51   save = errno;
  52   (void) close (fd2);
  53   __set_errno (save);
  54
  55   return fcntl (fd, F_DUPFD, fd2);
  56 }
  57 libc_hidden_def (__dup2)
  58 weak_alias (__dup2, dup2)