/* Adjust a file descriptor result so that it avoids clobbering

   STD{IN,OUT,ERR}_FILENO, with specific flags.

   Copyright (C) 2005-2006, 2009-2017 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Written by Paul Eggert and Eric Blake.  */

#include <config.h>

/* Specification.  */

#include "unistd-safer.h"

#include <errno.h>

#include <unistd.h>

/* Return FD, unless FD would be a copy of standard input, output, or

   error; in that case, return a duplicate of FD, closing FD.  If FLAG

   contains O_CLOEXEC, the returned FD will have close-on-exec

   semantics.  On failure to duplicate, close FD, set errno, and

   return -1.  Preserve errno if FD is negative, so that the caller

   can always inspect errno when the returned value is negative.

   This function is usefully wrapped around functions that return file

   descriptors, e.g., fd_safer_flag (open ("file", O_RDONLY | flag), flag).  */

int

fd_safer_flag (int fd, int flag)

{

  if (STDIN_FILENO <= fd && fd <= STDERR_FILENO)

    {

      int f = dup_safer_flag (fd, flag);

      int e = errno;

      close (fd);

      errno = e;

      fd = f;

    }

  return fd;

}