/* save-cwd.c -- Save and restore current working directory.

   Copyright (C) 1995, 1997-1998, 2003-2006, 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 Jim Meyering.  */

#include <config.h>

#include "save-cwd.h"

#include <errno.h>

#include <fcntl.h>

#include <stdbool.h>

#include <stdio.h>

#include <stdlib.h>

#include "chdir-long.h"

#include "unistd--.h"

#include "cloexec.h"

#if GNULIB_FCNTL_SAFER

# include "fcntl--.h"

#else

# define GNULIB_FCNTL_SAFER 0

#endif

/* Record the location of the current working directory in CWD so that

   the program may change to other directories and later use restore_cwd

   to return to the recorded location.  This function may allocate

   space using malloc (via getcwd) or leave a file descriptor open;

   use free_cwd to perform the necessary free or close.  Upon failure,

   no memory is allocated, any locally opened file descriptors are

   closed;  return non-zero -- in that case, free_cwd need not be

   called, but doing so is ok.  Otherwise, return zero.

   The _raison d'etre_ for this interface is that the working directory

   is sometimes inaccessible, and getcwd is not robust or as efficient.

   So, we prefer to use the open/fchdir approach, but fall back on

   getcwd if necessary.  This module works for most cases with just

   the getcwd-lgpl module, but to be truly robust, use the getcwd module.

   Some systems lack fchdir altogether: e.g., OS/2, pre-2001 Cygwin,

   SCO Xenix.  Also, SunOS 4 and Irix 5.3 provide the function, yet it

   doesn't work for partitions on which auditing is enabled.  If

   you're still using an obsolete system with these problems, please

   send email to the maintainer of this code.  */

int

save_cwd (struct saved_cwd *cwd)

{

  cwd->name = NULL;

  cwd->desc = open (".", O_SEARCH);

  if (!GNULIB_FCNTL_SAFER)

    cwd->desc = fd_safer (cwd->desc);

  if (cwd->desc < 0)

    {

      cwd->name = getcwd (NULL, 0);

      return cwd->name ? 0 : -1;

    }

  set_cloexec_flag (cwd->desc, true);

  return 0;

}

/* Change to recorded location, CWD, in directory hierarchy.

   Upon failure, return -1 (errno is set by chdir or fchdir).

   Upon success, return zero.  */

int

restore_cwd (const struct saved_cwd *cwd)

{

  if (0 <= cwd->desc)

    return fchdir (cwd->desc);

  else

    return chdir_long (cwd->name);

}

void

free_cwd (struct saved_cwd *cwd)

{

  if (cwd->desc >= 0)

    close (cwd->desc);

  free (cwd->name);

}