sysdeps/unix/sysv/linux/dup2.c

   1 /* Duplicate a file descriptor.  Linux version.
   2    Copyright (C) 2011-2024 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <fcntl.h>
  20 #include <unistd.h>
  21 #include <sysdep.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 #ifdef __NR_dup2
  29   return INLINE_SYSCALL_CALL (dup2, fd, fd2);
  30 #else
  31   /* For the degenerate case, check if the fd is valid (by trying to
  32      get the file status flags) and return it, or else return EBADF.  */
  33   if (fd == fd2)
  34     return __libc_fcntl (fd, F_GETFL, 0) < 0 ? -1 : fd;
  35
  36   return INLINE_SYSCALL_CALL (dup3, fd, fd2, 0);
  37 #endif
  38 }
  39 libc_hidden_def (__dup2)
  40 weak_alias (__dup2, dup2)