lib/targetdir.c

/* Target directory operands for coreutils

   Copyright 2004-2025 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/>.  */

#include <config.h>

#define TARGETDIR_INLINE _GL_EXTERN_INLINE
#include <targetdir.h>

#include <attribute.h>

#include <errno.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>

#ifdef O_PATH
enum { O_PATHSEARCH = O_PATH };
#else
enum { O_PATHSEARCH = O_SEARCH };
#endif

/* Must F designate the working directory?  */

ATTRIBUTE_PURE static bool
must_be_working_directory (char const *f)
{
  /* Return true for ".", "./.", ".///./", etc.  */
  while (*f++ == '.')
    {
      if (*f != '/')
        return !*f;
      while (*++f == '/')
        continue;
      if (!*f)
        return true;
    }
  return false;
}

/* Return a file descriptor open to FILE, for use in openat.
   As an optimization, return AT_FDCWD if FILE must be the working directory.
   As a side effect, possibly set *ST to the file's status.
   Fail and set errno if FILE is not a directory.
   On failure return -2 if AT_FDCWD is -1, -1 otherwise.  */

int
target_directory_operand (char const *file, struct stat *st)
{
  if (must_be_working_directory (file))
    return AT_FDCWD;

  int fd = open (file, O_PATHSEARCH | O_DIRECTORY);

  /* On platforms lacking O_PATH, using O_SEARCH | O_DIRECTORY to
     open an overly-protected non-directory can fail with either
     EACCES or ENOTDIR.  Prefer ENOTDIR as it makes for better
     diagnostics.  */
  if (O_PATHSEARCH == O_SEARCH && fd < 0 && errno == EACCES)
    errno = stat (file, st) < 0 || S_ISDIR (st->st_mode) ? EACCES : ENOTDIR;

  return fd - (AT_FDCWD == -1 && fd < 0);
}