1  /* Open a directory relative to another directory.
       2  
       3     Copyright 2006-2023 Free Software Foundation, Inc.
       4  
       5     This program is free software: you can redistribute it and/or modify
       6     it under the terms of the GNU General Public License as published by
       7     the Free Software Foundation, either version 3 of the License, or
       8     (at your option) any later version.
       9  
      10     This program 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
      13     GNU General Public License for more details.
      14  
      15     You should have received a copy of the GNU General Public License
      16     along with this program.  If not, see <https://www.gnu.org/licenses/>.
      17  
      18     Written by Jim Meyering and Paul Eggert.  */
      19  
      20  #include <config.h>
      21  
      22  #include <opendirat.h>
      23  
      24  #include <errno.h>
      25  #include <fcntl--.h>
      26  #include <unistd.h>
      27  
      28  /* Relative to DIR_FD, open the directory DIR, passing EXTRA_FLAGS to
      29     the underlying openat call.  On success, store into *PNEW_FD the
      30     underlying file descriptor of the newly opened directory and return
      31     the directory stream.  On failure, return NULL and set errno.
      32  
      33     On success, *PNEW_FD is at least 3, so this is a "safer" function.  */
      34  
      35  DIR *
      36  opendirat (int dir_fd, char const *dir, int extra_flags, int *pnew_fd)
      37  {
      38    int open_flags = (O_RDONLY | O_CLOEXEC | O_DIRECTORY | O_NOCTTY
      39                      | O_NONBLOCK | extra_flags);
      40    int new_fd = openat (dir_fd, dir, open_flags);
      41  
      42    if (new_fd < 0)
      43      return NULL;
      44    DIR *dirp = fdopendir (new_fd);
      45    if (dirp)
      46      *pnew_fd = new_fd;
      47    else
      48      {
      49        int fdopendir_errno = errno;
      50        close (new_fd);
      51        errno = fdopendir_errno;
      52      }
      53    return dirp;
      54  }