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bc511a64f6
Most of this change is to boilerplate commentary such as license URLs. This change was prompted by ftp://ftp.gnu.org's going-away party, planned for November. Change these FTP URLs to https://ftp.gnu.org instead. Make similar changes for URLs to other organizations moving away from FTP. Also, change HTTP to HTTPS for URLs to gnu.org and fsf.org when this works, as this will further help defend against man-in-the-middle attacks (for this part I omitted the MS-DOS and MS-Windows sources and the test tarballs to keep the workload down). HTTPS is not fully working to lists.gnu.org so I left those URLs alone for now.
90 lines
3.3 KiB
C
90 lines
3.3 KiB
C
/* save-cwd.c -- Save and restore current working directory.
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Copyright (C) 1995, 1997-1998, 2003-2006, 2009-2017 Free Software
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Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Gnulib needs to save and restore the current working directory to
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fully emulate functions like fstatat. But Emacs doesn't care what
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the current working directory is; it always uses absolute file
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names. This module replaces the Gnulib module by omitting the code
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that Emacs does not need. */
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#include <config.h>
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#include "save-cwd.h"
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#include <fcntl.h>
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#include <unistd.h>
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/* Record the location of the current working directory in CWD so that
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the program may change to other directories and later use restore_cwd
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to return to the recorded location. This function may allocate
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space using malloc (via getcwd) or leave a file descriptor open;
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use free_cwd to perform the necessary free or close. Upon failure,
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no memory is allocated, any locally opened file descriptors are
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closed; return non-zero -- in that case, free_cwd need not be
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called, but doing so is ok. Otherwise, return zero.
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The _raison d'etre_ for this interface is that the working directory
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is sometimes inaccessible, and getcwd is not robust or as efficient.
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So, we prefer to use the open/fchdir approach, but fall back on
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getcwd if necessary. This module works for most cases with just
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the getcwd-lgpl module, but to be truly robust, use the getcwd module.
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Some systems lack fchdir altogether: e.g., OS/2, pre-2001 Cygwin,
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SCO Xenix. Also, SunOS 4 and Irix 5.3 provide the function, yet it
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doesn't work for partitions on which auditing is enabled. If
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you're still using an obsolete system with these problems, please
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send email to the maintainer of this code. */
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#if !defined HAVE_FCHDIR && !defined fchdir
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# define fchdir(fd) (-1)
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#endif
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int
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save_cwd (struct saved_cwd *cwd)
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{
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cwd->desc = open (".", O_SEARCH | O_CLOEXEC);
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/* The 'name' member is present only to minimize differences from
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gnulib. Initialize it to zero, if only to simplify debugging. */
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cwd->name = 0;
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return 0;
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}
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/* Change to recorded location, CWD, in directory hierarchy.
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Upon failure, return -1 (errno is set by chdir or fchdir).
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Upon success, return zero. */
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int
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restore_cwd (const struct saved_cwd *cwd)
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{
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/* Restore the previous directory if possible, to avoid tying down
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the file system of the new directory (Bug#18232).
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Don't worry if fchdir fails, as Emacs doesn't care what the
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working directory is. The fchdir call is inside an 'if' merely to
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pacify compilers that complain if fchdir's return value is ignored. */
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if (fchdir (cwd->desc) == 0)
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return 0;
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return 0;
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}
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void
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free_cwd (struct saved_cwd *cwd)
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{
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close (cwd->desc);
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}
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