1 /* save-cwd.c -- Save and restore current working directory. 2 3 Copyright (C) 1995, 1997, 1998, 2003, 2004, 2005 Free Software 4 Foundation, Inc. 5 6 This program is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program; if not, write to the Free Software Foundation, 18 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ 19 20 /* Written by Jim Meyering. */ 21 22 #ifdef HAVE_CONFIG_H 23 # include <config.h> 24 #endif 25 26 #include "save-cwd.h" 27 28 #include <stdbool.h> 29 #include <stdio.h> 30 #include <stdlib.h> 31 32 #if HAVE_UNISTD_H 33 # include <unistd.h> 34 #endif 35 36 #include <fcntl.h> 37 38 #include <errno.h> 39 40 #include "unistd-safer.h" 41 #include "xgetcwd.h" 42 43 /* On systems without the fchdir function (WOE), pretend that open 44 always returns -1 so that save_cwd resorts to using xgetcwd. 45 Since chdir_long requires fchdir, use chdir instead. */ 46 #if !HAVE_FCHDIR 47 # undef open 48 # define open(File, Flags) (-1) 49 # undef fchdir 50 # define fchdir(Fd) (abort (), -1) 51 # undef chdir_long 52 # define chdir_long(Dir) chdir (Dir) 53 #endif 54 55 /* Record the location of the current working directory in CWD so that 56 the program may change to other directories and later use restore_cwd 57 to return to the recorded location. This function may allocate 58 space using malloc (via xgetcwd) or leave a file descriptor open; 59 use free_cwd to perform the necessary free or close. Upon failure, 60 no memory is allocated, any locally opened file descriptors are 61 closed; return non-zero -- in that case, free_cwd need not be 62 called, but doing so is ok. Otherwise, return zero. 63 64 The `raison d'etre' for this interface is that the working directory 65 is sometimes inaccessible, and getcwd is not robust or as efficient. 66 So, we prefer to use the open/fchdir approach, but fall back on 67 getcwd if necessary. 68 69 Some systems lack fchdir altogether: e.g., OS/2, pre-2001 Cygwin, 70 SCO Xenix. Also, SunOS 4 and Irix 5.3 provide the function, yet it 71 doesn't work for partitions on which auditing is enabled. If 72 you're still using an obsolete system with these problems, please 73 send email to the maintainer of this code. */ 74 75 int 76 save_cwd (struct saved_cwd *cwd) 77 { 78 cwd->name = NULL; 79 80 cwd->desc = fd_safer (open (".", O_RDONLY)); 81 if (cwd->desc < 0) 82 { 83 cwd->desc = fd_safer (open (".", O_WRONLY)); 84 if (cwd->desc < 0) 85 { 86 cwd->name = xgetcwd (); 87 return cwd->name ? 0 : -1; 88 } 89 } 90 91 return 0; 92 } 93 94 /* Change to recorded location, CWD, in directory hierarchy. 95 Upon failure, return -1 (errno is set by chdir or fchdir). 96 Upon success, return zero. */ 97 98 int 99 restore_cwd (const struct saved_cwd *cwd) 100 { 101 if (0 <= cwd->desc) 102 return fchdir (cwd->desc); 103 else 104 return -1; 105 } 106 107 void 108 free_cwd (struct saved_cwd *cwd) 109 { 110 if (cwd->desc >= 0) 111 close (cwd->desc); 112 if (cwd->name) 113 free (cwd->name); 114 } 115