1 /* save-cwd.c -- Save and restore current working directory. 2 3 Copyright (C) 1995, 1997-1998, 2003-2006, 2009-2021 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 <https://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 34 #if GNULIB_FCNTL_SAFER 35 # include "fcntl--.h" 36 #else 37 # define GNULIB_FCNTL_SAFER 0 38 #endif 39 40 /* Record the location of the current working directory in CWD so that 41 the program may change to other directories and later use restore_cwd 42 to return to the recorded location. This function may allocate 43 space using malloc (via getcwd) or leave a file descriptor open; 44 use free_cwd to perform the necessary free or close. Upon failure, 45 no memory is allocated, any locally opened file descriptors are 46 closed; return non-zero -- in that case, free_cwd need not be 47 called, but doing so is ok. Otherwise, return zero. 48 49 The _raison d'etre_ for this interface is that the working directory 50 is sometimes inaccessible, and getcwd is not robust or as efficient. 51 So, we prefer to use the open/fchdir approach, but fall back on 52 getcwd if necessary. This module works for most cases with just 53 the getcwd-lgpl module, but to be truly robust, use the getcwd module. 54 55 Some systems lack fchdir altogether: e.g., OS/2, pre-2001 Cygwin, 56 SCO Xenix. Also, SunOS 4 and Irix 5.3 provide the function, yet it 57 doesn't work for partitions on which auditing is enabled. If 58 you're still using an obsolete system with these problems, please 59 send email to the maintainer of this code. */ 60 61 int 62 save_cwd (struct saved_cwd *cwd) /* */ 63 { 64 cwd->name = NULL; 65 66 cwd->desc = open (".", O_SEARCH | O_CLOEXEC); 67 if (!GNULIB_FCNTL_SAFER) 68 cwd->desc = fd_safer_flag (cwd->desc, O_CLOEXEC); 69 if (cwd->desc < 0) 70 { 71 cwd->name = getcwd (NULL, 0); 72 return cwd->name ? 0 : -1; 73 } 74 75 return 0; 76 } 77 78 /* Change to recorded location, CWD, in directory hierarchy. 79 Upon failure, return -1 (errno is set by chdir or fchdir). 80 Upon success, return zero. */ 81 82 int 83 restore_cwd (const struct saved_cwd *cwd) /* */ 84 { 85 if (0 <= cwd->desc) 86 return fchdir (cwd->desc); 87 else 88 return chdir_long (cwd->name); 89 } 90 91 void 92 free_cwd (struct saved_cwd *cwd) /* */ 93 { 94 if (cwd->desc >= 0) 95 close (cwd->desc); 96 free (cwd->name); 97 }