lib/save-cwd.c

   1 /* save-cwd.c -- Save and restore current working directory.
   2    Copyright (C) 1995, 1997 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 <meyering@na-net.ornl.gov>.  */
  19
  20 #ifdef HAVE_CONFIG_H
  21 # include "config.h"
  22 #endif
  23
  24 #include <stdio.h>
  25
  26 #ifdef STDC_HEADERS
  27 # include <stdlib.h>
  28 #endif
  29
  30 #ifdef HAVE_UNISTD_H
  31 # include <unistd.h>
  32 #endif
  33
  34 #ifdef HAVE_FCNTL_H
  35 # include <fcntl.h>
  36 #else
  37 # include <sys/file.h>
  38 #endif
  39
  40 #include <errno.h>
  41 #ifndef errno
  42 extern int errno;
  43 #endif
  44
  45 #include "save-cwd.h"
  46 #include "error.h"
  47
  48 char *xgetcwd __P((void));
  49
  50 /* Record the location of the current working directory in CWD so that
  51    the program may change to other directories and later use restore_cwd
  52    to return to the recorded location.  This function may allocate
  53    space using malloc (via xgetcwd) or leave a file descriptor open;
  54    use free_cwd to perform the necessary free or close.  Upon failure,
  55    no memory is allocated, any locally opened file descriptors are
  56    closed;  return non-zero -- in that case, free_cwd need not be
  57    called, but doing so is ok.  Otherwise, return zero.  */
  58
  59 int
  60 save_cwd (cwd)
  61      struct saved_cwd *cwd;
  62 {
  63   static int have_working_fchdir = 1;
  64
  65   cwd->desc = -1;
  66   cwd->name = NULL;
  67
  68   if (have_working_fchdir)
  69     {
  70 #ifdef HAVE_FCHDIR
  71       cwd->desc = open (".", O_RDONLY);
  72       if (cwd->desc < 0)
  73         {
  74           error (0, errno, "cannot open current directory");
  75           return 1;
  76         }
  77
  78 # if __sun__ || sun
  79       /* On SunOS 4, fchdir returns EINVAL if accounting is enabled,
  80          so we have to fall back to chdir.  */
  81       if (fchdir (cwd->desc))
  82         {
  83           if (errno == EINVAL)
  84             {
  85               close (cwd->desc);
  86               cwd->desc = -1;
  87               have_working_fchdir = 0;
  88             }
  89           else
  90             {
  91               error (0, errno, "current directory");
  92               close (cwd->desc);
  93               cwd->desc = -1;
  94               return 1;
  95             }
  96         }
  97 # endif /* __sun__ || sun */
  98 #else
  99 # define fchdir(x) (abort (), 0)
 100       have_working_fchdir = 0;
 101 #endif
 102     }
 103
 104   if (!have_working_fchdir)
 105     {
 106       cwd->name = xgetcwd ();
 107       if (cwd->name == NULL)
 108         {
 109           error (0, errno, "cannot get current directory");
 110           return 1;
 111         }
 112     }
 113   return 0;
 114 }
 115
 116 /* Change to recorded location, CWD, in directory hierarchy.
 117    If "saved working directory", NULL))
 118    */
 119
 120 int
 121 restore_cwd (cwd, dest, from)
 122      const struct saved_cwd *cwd;
 123      const char *dest;
 124      const char *from;
 125 {
 126   int fail = 0;
 127   if (cwd->desc >= 0)
 128     {
 129       if (fchdir (cwd->desc))
 130         {
 131           error (0, errno, "cannot return to %s%s%s",
 132                  (dest ? dest : "saved working directory"),
 133                  (from ? " from " : ""),
 134                  (from ? from : ""));
 135           fail = 1;
 136         }
 137     }
 138   else if (chdir (cwd->name) < 0)
 139     {
 140       error (0, errno, "%s", cwd->name);
 141       fail = 1;
 142     }
 143   return fail;
 144 }
 145
 146 void
 147 free_cwd (cwd)
 148      struct saved_cwd *cwd;
 149 {
 150   if (cwd->desc >= 0)
 151     close (cwd->desc);
 152   if (cwd->name)
 153     free (cwd->name);
 154 }