sysdeps/posix/dup2.c

   1 /* Copyright (C) 1991, 92, 93, 95, 96 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 <fcntl.h>
  21 #include <limits.h>
  22 #include <unistd.h>
  23
  24
  25 /* Duplicate FD to FD2, closing the old FD2 and making FD2 be
  26    open the same file as FD is.  Return FD2 or -1.  */
  27 int
  28 __dup2 (fd, fd2)
  29      int fd;
  30      int fd2;
  31 {
  32   int save;
  33
  34   if (fd2 < 0
  35 #ifdef OPEN_MAX
  36       || fd2 >= OPEN_MAX
  37 #endif
  38 )
  39     {
  40       __set_errno (EBADF);
  41       return -1;
  42     }
  43
  44   /* Check if FD is kosher.  */
  45   if (fcntl (fd, F_GETFL) < 0)
  46     return -1;
  47
  48   if (fd == fd2)
  49     return fd2;
  50
  51   /* This is not atomic.  */
  52
  53   save = errno;
  54   (void) close (fd2);
  55   __set_errno (save);
  56
  57   return fcntl (fd, F_DUPFD, fd2);
  58 }
  59
  60 weak_alias (__dup2, dup2)