Function resolve_symlinks

src/common/exec.c:234–319

* resolve_symlinks - resolve symlinks to the underlying file * * Replace "path" by the absolute path to the referenced file. * * Returns 0 if OK, -1 if error. * * Note: we are not particularly tense about producing nice error messages * because we are not really expecting error here; we just determined that * the symlink does point to a valid executable. */

 * the symlink does point to a valid executable.
 */
static int
resolve_symlinks(char *path)
{
#ifdef HAVE_READLINK
	struct stat buf;
	char		orig_wd[MAXPGPATH],
				link_buf[MAXPGPATH];
	char	   *fname;

	/*
	 * To resolve a symlink properly, we have to chdir into its directory and
	 * then chdir to where the symlink points; otherwise we may fail to
	 * resolve relative links correctly (consider cases involving mount
	 * points, for example).  After following the final symlink, we use
	 * getcwd() to figure out where the heck we're at.
	 *
	 * One might think we could skip all this if path doesn't point to a
	 * symlink to start with, but that's wrong.  We also want to get rid of
	 * any directory symlinks that are present in the given path. We expect
	 * getcwd() to give us an accurate, symlink-free path.
	 */
	if (!getcwd(orig_wd, MAXPGPATH))
	{
		log_error(errcode_for_file_access(),
				  _("could not identify current directory: %m"));
		return -1;
	}

	for (;;)
	{
		char	   *lsep;
		int			rllen;

		lsep = last_dir_separator(path);
		if (lsep)
		{
			*lsep = '\0';
			if (chdir(path) == -1)
			{
				log_error(errcode_for_file_access(),
						  _("could not change directory to \"%s\": %m"), path);
				return -1;
			}
			fname = lsep + 1;
		}
		else
			fname = path;

		if (lstat(fname, &buf) < 0 ||
			!S_ISLNK(buf.st_mode))
			break;

		errno = 0;
		rllen = readlink(fname, link_buf, sizeof(link_buf));
		if (rllen < 0 || rllen >= sizeof(link_buf))
		{
			log_error(errcode_for_file_access(),
					  _("could not read symbolic link \"%s\": %m"), fname);