lib/mknodat.c

/* Create an inode relative to an open directory.
   Copyright (C) 2009-2026 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 <https://www.gnu.org/licenses/>.  */

/* written by Eric Blake */

#include <config.h>

/* Specification.  */
#include <sys/stat.h>

#include <stdlib.h>

#if HAVE_MKNODAT

# include <errno.h>
# include <fcntl.h>
# include <string.h>

int
rpl_mknodat (int fd, char const *file, mode_t mode, dev_t dev)
#undef mknodat
{
  /* Use the original mknodat(), but correct the trailing slash handling.  */
  size_t len = strlen (file);
  if (len && file[len - 1] == '/')
    {
      struct stat st;

      if (fstatat (fd, file, &st, AT_SYMLINK_NOFOLLOW) < 0)
        {
          if (errno == EOVERFLOW)
            /* It's surely a file, not a directory.  */
            errno = ENOTDIR;
        }
      else
        {
          /* It's a directory, otherwise fstatat() would have reported an error
             ENOTDIR.  */
          errno = EEXIST;
        }
      return -1;
    }

# if defined __HAIKU__
  /* POSIX requires mknodat to create fifos for non-privileged processes, but
     on Haiku it fails with ENOTSUP.  */
  if (S_ISFIFO (mode) && dev == 0)
    return mkfifo (file, mode & ~S_IFIFO);
# endif
  return mknodat (fd, file, mode, dev);
}

#else

# if !HAVE_MKNOD

#  include <errno.h>

/* Mingw lacks mknod, so this wrapper is trivial.  */

int
mknodat (_GL_UNUSED int fd, _GL_UNUSED char const *path,
         _GL_UNUSED mode_t mode, _GL_UNUSED dev_t dev)
{
  errno = ENOSYS;
  return -1;
}

# else

/* Create a file system node FILE relative to directory FD, with
   access permissions and file type in MODE, and device type in DEV.
   Usually, non-root applications can only create named fifos, with
   DEV set to 0.  If possible, create the node without changing the
   working directory.  Otherwise, resort to using save_cwd/fchdir,
   then mknod/restore_cwd.  If either the save_cwd or the restore_cwd
   fails, then give a diagnostic and exit nonzero.  */

#  define AT_FUNC_NAME mknodat
#  define AT_FUNC_F1 mknod
#  define AT_FUNC_POST_FILE_PARAM_DECLS , mode_t mode, dev_t dev
#  define AT_FUNC_POST_FILE_ARGS        , mode, dev
#  include "at-func.c"
#  undef AT_FUNC_NAME
#  undef AT_FUNC_F1
#  undef AT_FUNC_POST_FILE_PARAM_DECLS
#  undef AT_FUNC_POST_FILE_ARGS

# endif

#endif