1  /* Copyright (C) 1991-2023 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     <https://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 (int fd, int fd2)
      27  {
      28    int save;
      29  
      30    if (fd2 < 0
      31  #ifdef OPEN_MAX
      32        || fd2 >= OPEN_MAX
      33  #endif
      34  )
      35      {
      36        __set_errno (EBADF);
      37        return -1;
      38      }
      39  
      40    /* Check if FD is kosher.  */
      41    if (fcntl (fd, F_GETFL) < 0)
      42      return -1;
      43  
      44    if (fd == fd2)
      45      return fd2;
      46  
      47    /* This is not atomic.  */
      48  
      49    save = errno;
      50    (void) close (fd2);
      51    __set_errno (save);
      52  
      53    return fcntl (fd, F_DUPFD, fd2);
      54  }
      55  libc_hidden_def (__dup2)
      56  weak_alias (__dup2, dup2)