lib/save-cwd.c

   1 /* save-cwd.c -- Save and restore current working directory.
   2    Copyright (C) 1995, 1997, 1998, 2003, 2004 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 "save-cwd.h"
  25
  26 #include <stdbool.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29
  30 #if HAVE_UNISTD_H
  31 # include <unistd.h>
  32 #endif
  33
  34 #if HAVE_FCNTL_H
  35 # include <fcntl.h>
  36 #else
  37 # include <sys/file.h>
  38 #endif
  39
  40 #include <errno.h>
  41
  42 #include "chdir-long.h"
  43 #include "xgetcwd.h"
  44
  45 /* Record the location of the current working directory in CWD so that
  46    the program may change to other directories and later use restore_cwd
  47    to return to the recorded location.  This function may allocate
  48    space using malloc (via xgetcwd) or leave a file descriptor open;
  49    use free_cwd to perform the necessary free or close.  Upon failure,
  50    no memory is allocated, any locally opened file descriptors are
  51    closed;  return non-zero -- in that case, free_cwd need not be
  52    called, but doing so is ok.  Otherwise, return zero.
  53
  54    The `raison d'etre' for this interface is that some systems lack
  55    support for fchdir, and getcwd is not robust or as efficient.
  56    So, we prefer to use the open/fchdir approach, but fall back on
  57    getcwd if necessary.  Some systems lack fchdir altogether: OS/2,
  58    Cygwin (as of March 2003), SCO Xenix.  At least SunOS 4 and Irix 5.3
  59    provide the function, yet it doesn't work for partitions on which
  60    auditing is enabled.  */
  61
  62 int
  63 save_cwd (struct saved_cwd *cwd)
  64 {
  65 #if !HAVE_FCHDIR
  66 # undef fchdir
  67 # define fchdir(x) (abort (), 0)
  68   bool have_working_fchdir = false;
  69   bool fchdir_needs_testing = false;
  70 #elif (__sgi || __sun)
  71   static bool have_working_fchdir = true;
  72   bool fchdir_needs_testing = true;
  73 #else
  74   bool have_working_fchdir = true;
  75   bool fchdir_needs_testing = false;
  76 #endif
  77
  78   cwd->desc = -1;
  79   cwd->name = NULL;
  80
  81   if (have_working_fchdir)
  82     {
  83       cwd->desc = open (".", O_RDONLY);
  84       if (cwd->desc < 0)
  85         {
  86           cwd->desc = open (".", O_WRONLY);
  87           if (cwd->desc < 0)
  88             {
  89               cwd->name = xgetcwd ();
  90               return cwd->name ? 0 : -1;
  91             }
  92         }
  93
  94       /* On SunOS 4 and IRIX 5.3, fchdir returns EINVAL when auditing
  95          is enabled, so we have to fall back to chdir.  */
  96       if (fchdir_needs_testing && fchdir (cwd->desc) != 0)
  97         {
  98           int saved_errno = errno;
  99           close (cwd->desc);
 100           cwd->desc = -1;
 101           if (saved_errno != EINVAL)
 102             {
 103               errno = saved_errno;
 104               return -1;
 105             }
 106           have_working_fchdir = false;
 107         }
 108     }
 109
 110   if (!have_working_fchdir)
 111     {
 112       cwd->name = xgetcwd ();
 113       if (cwd->name == NULL)
 114         return -1;
 115     }
 116   return 0;
 117 }
 118
 119 /* Change to recorded location, CWD, in directory hierarchy.
 120    Upon failure, return -1 (errno is set by chdir or fchdir).
 121    Upon success, return zero.  */
 122
 123 int
 124 restore_cwd (const struct saved_cwd *cwd)
 125 {
 126   if (0 <= cwd->desc)
 127     return fchdir (cwd->desc);
 128   else
 129     return chdir_long (cwd->name);
 130 }
 131
 132 void
 133 free_cwd (struct saved_cwd *cwd)
 134 {
 135   if (cwd->desc >= 0)
 136     close (cwd->desc);
 137   if (cwd->name)
 138     free (cwd->name);
 139 }