1 /* save-cwd.c -- Save and restore current working directory. 2 3 Copyright (C) 1995, 1997-1998, 2003-2006, 2009-2014 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 3 of the License, or 9 (at your option) 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, see <http://www.gnu.org/licenses/>. */ 18 19 /* Written by Jim Meyering. */ 20 21 #include <config.h> 22 23 #include "save-cwd.h" 24 25 #include <errno.h> 26 #include <fcntl.h> 27 #include <stdbool.h> 28 #include <stdio.h> 29 #include <stdlib.h> 30 31 #include "chdir-long.h" 32 #include "unistd--.h" 33 #include "cloexec.h" 34 35 #if GNULIB_FCNTL_SAFER 36 # include "fcntl--.h" 37 #else 38 # define GNULIB_FCNTL_SAFER 0 39 #endif 40 41 /* Record the location of the current working directory in CWD so that 42 the program may change to other directories and later use restore_cwd 43 to return to the recorded location. This function may allocate 44 space using malloc (via getcwd) or leave a file descriptor open; 45 use free_cwd to perform the necessary free or close. Upon failure, 46 no memory is allocated, any locally opened file descriptors are 47 closed; return non-zero -- in that case, free_cwd need not be 48 called, but doing so is ok. Otherwise, return zero. 49 50 The _raison d'etre_ for this interface is that the working directory 51 is sometimes inaccessible, and getcwd is not robust or as efficient. 52 So, we prefer to use the open/fchdir approach, but fall back on 53 getcwd if necessary. This module works for most cases with just 54 the getcwd-lgpl module, but to be truly robust, use the getcwd module. 55 56 Some systems lack fchdir altogether: e.g., OS/2, pre-2001 Cygwin, 57 SCO Xenix. Also, SunOS 4 and Irix 5.3 provide the function, yet it 58 doesn't work for partitions on which auditing is enabled. If 59 you're still using an obsolete system with these problems, please 60 send email to the maintainer of this code. */ 61 62 int 63 save_cwd (struct saved_cwd *cwd) 64 { 65 cwd->name = NULL; 66 67 cwd->desc = open (".", O_SEARCH); 68 if (!GNULIB_FCNTL_SAFER) 69 cwd->desc = fd_safer (cwd->desc); 70 if (cwd->desc < 0) 71 { 72 cwd->name = getcwd (NULL, 0); 73 return cwd->name ? 0 : -1; 74 } 75 76 set_cloexec_flag (cwd->desc, true); 77 return 0; 78 } 79 80 /* Change to recorded location, CWD, in directory hierarchy. 81 Upon failure, return -1 (errno is set by chdir or fchdir). 82 Upon success, return zero. */ 83 84 int 85 restore_cwd (const struct saved_cwd *cwd) 86 { 87 if (0 <= cwd->desc) 88 return fchdir (cwd->desc); 89 else 90 return chdir_long (cwd->name); 91 } 92 93 void 94 free_cwd (struct saved_cwd *cwd) 95 { 96 if (cwd->desc >= 0) 97 close (cwd->desc); 98 free (cwd->name); 99 } 100