lib/save-cwd.c

   1 /* save-cwd.c -- Save and restore current working directory.
   2    Copyright (C) 1995, 1997, 1998, 2003 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* Written by Jim Meyering.  */
  19
  20 #if HAVE_CONFIG_H
  21 # include "config.h"
  22 #endif
  23
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26
  27 #if HAVE_UNISTD_H
  28 # include <unistd.h>
  29 #endif
  30
  31 #if HAVE_FCNTL_H
  32 # include <fcntl.h>
  33 #else
  34 # include <sys/file.h>
  35 #endif
  36
  37 #include <errno.h>
  38 #ifndef errno
  39 extern int errno;
  40 #endif
  41
  42 #ifndef O_DIRECTORY
  43 # define O_DIRECTORY 0
  44 #endif
  45
  46 #include "save-cwd.h"
  47 #include "xgetcwd.h"
  48
  49 /* Record the location of the current working directory in CWD so that
  50    the program may change to other directories and later use restore_cwd
  51    to return to the recorded location.  This function may allocate
  52    space using malloc (via xgetcwd) or leave a file descriptor open;
  53    use free_cwd to perform the necessary free or close.  Upon failure,
  54    no memory is allocated, any locally opened file descriptors are
  55    closed;  return non-zero -- in that case, free_cwd need not be
  56    called, but doing so is ok.  Otherwise, return zero.
  57
  58    The `raison d'etre' for this interface is that some systems lack
  59    support for fchdir, and getcwd is not robust or as efficient.
  60    So, we prefer to use the open/fchdir approach, but fall back on
  61    getcwd if necessary.  Some systems lack fchdir altogether: OS/2,
  62    Cygwin (as of March 2003), SCO Xenix.  At least SunOS 4 and Irix 5.3
  63    provide the function, yet it doesn't work for partitions on which
  64    auditing is enabled.  */
  65
  66 int
  67 save_cwd (struct saved_cwd *cwd)
  68 {
  69   static int have_working_fchdir = 1;
  70
  71   cwd->desc = -1;
  72   cwd->name = NULL;
  73
  74   if (have_working_fchdir)
  75     {
  76 #if HAVE_FCHDIR
  77       cwd->desc = open (".", O_RDONLY | O_DIRECTORY);
  78       if (cwd->desc < 0)
  79         return 1;
  80
  81 # if __sun__ || sun
  82       /* On SunOS 4 and IRIX 5.3, fchdir returns EINVAL when auditing
  83          is enabled, so we have to fall back to chdir.  */
  84       if (fchdir (cwd->desc))
  85         {
  86           if (errno == EINVAL)
  87             {
  88               close (cwd->desc);
  89               cwd->desc = -1;
  90               have_working_fchdir = 0;
  91             }
  92           else
  93             {
  94               int saved_errno = errno;
  95               close (cwd->desc);
  96               cwd->desc = -1;
  97               errno = saved_errno;
  98               return 1;
  99             }
 100         }
 101 # endif /* __sun__ || sun */
 102 #else
 103 # define fchdir(x) (abort (), 0)
 104       have_working_fchdir = 0;
 105 #endif
 106     }
 107
 108   if (!have_working_fchdir)
 109     {
 110       cwd->name = xgetcwd ();
 111       if (cwd->name == NULL)
 112         return 1;
 113     }
 114   return 0;
 115 }
 116
 117 /* Change to recorded location, CWD, in directory hierarchy.
 118    Upon failure, return nonzero (errno is set by chdir or fchdir).
 119    Upon success, return zero.  */
 120
 121 int
 122 restore_cwd (const struct saved_cwd *cwd)
 123 {
 124   if (0 <= cwd->desc)
 125     return fchdir (cwd->desc) < 0;
 126   else
 127     return chdir (cwd->name) < 0;
 128 }
 129
 130 void
 131 free_cwd (struct saved_cwd *cwd)
 132 {
 133   if (cwd->desc >= 0)
 134     close (cwd->desc);
 135   if (cwd->name)
 136     free (cwd->name);
 137 }