sysdeps/posix/dup2.c

   1 /* Copyright (C) 1991, 92, 93, 95, 96, 97, 2002 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 <fcntl.h>
  21 #include <limits.h>
  22 #include <unistd.h>
  23
  24 /* Duplicate FD to FD2, closing the old FD2 and making FD2 be
  25    open the same file as FD is.  Return FD2 or -1.  */
  26 int
  27 __dup2 (fd, fd2)
  28      int fd;
  29      int fd2;
  30 {
  31   int save;
  32
  33   if (fd2 < 0
  34 #ifdef OPEN_MAX
  35       || fd2 >= OPEN_MAX
  36 #endif
  37 )
  38     {
  39       __set_errno (EBADF);
  40       return -1;
  41     }
  42
  43   /* Check if FD is kosher.  */
  44   if (fcntl (fd, F_GETFL) < 0)
  45     return -1;
  46
  47   if (fd == fd2)
  48     return fd2;
  49
  50   /* This is not atomic.  */
  51
  52   save = errno;
  53   (void) close (fd2);
  54   __set_errno (save);
  55
  56   return fcntl (fd, F_DUPFD, fd2);
  57 }
  58 libc_hidden_def (__dup2)
  59 weak_alias (__dup2, dup2)