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1 | /* save-cwd.c -- Save and restore current working directory. | |
2 | ||
3 | Copyright (C) 1995, 1997-1998, 2003-2006, 2009-2016 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 | } |