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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 17:39:29 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 17:39:29 +0000
commit8ffec2a3aba6f114784e11f89ef1d57a096ae540 (patch)
treeccebcbad06203e8241a8e7249f8e6c478a3682ea /lib/readlinkat.c
parentInitial commit. (diff)
downloadcoreutils-8ffec2a3aba6f114784e11f89ef1d57a096ae540.tar.xz
coreutils-8ffec2a3aba6f114784e11f89ef1d57a096ae540.zip
Adding upstream version 8.32.upstream/8.32upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'lib/readlinkat.c')
-rw-r--r--lib/readlinkat.c82
1 files changed, 82 insertions, 0 deletions
diff --git a/lib/readlinkat.c b/lib/readlinkat.c
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+++ b/lib/readlinkat.c
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+/* Read a symlink relative to an open directory.
+ Copyright (C) 2009-2020 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+/* written by Eric Blake */
+
+#include <config.h>
+
+/* Specification. */
+#include <unistd.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#if HAVE_READLINKAT
+
+# undef readlinkat
+
+ssize_t
+rpl_readlinkat (int fd, char const *file, char *buf, size_t len)
+{
+# if READLINK_TRAILING_SLASH_BUG
+ size_t file_len = strlen (file);
+ if (file_len && file[file_len - 1] == '/')
+ {
+ /* Even if FILE without the slash is a symlink to a directory,
+ both lstat() and stat() must resolve the trailing slash to
+ the directory rather than the symlink. We can therefore
+ safely use stat() to distinguish between EINVAL and
+ ENOTDIR/ENOENT, avoiding extra overhead of rpl_lstat(). */
+ struct stat st;
+ if (stat (file, &st) == 0)
+ errno = EINVAL;
+ return -1;
+ }
+# endif /* READLINK_TRAILING_SLASH_BUG */
+ return readlinkat (fd, file, buf, len);
+}
+
+#else
+
+/* Gnulib provides a readlink stub for mingw; use it for distinction
+ between EINVAL and ENOENT, rather than always failing with ENOSYS. */
+
+/* POSIX 2008 says that unlike readlink, readlinkat returns 0 for
+ success instead of the buffer length. But this would render
+ readlinkat worthless since readlink does not guarantee a
+ NUL-terminated buffer. Assume this was a bug in POSIX. */
+
+/* Read the contents of symlink FILE into buffer BUF of size LEN, in the
+ directory open on descriptor FD. If possible, do it without changing
+ the working directory. Otherwise, resort to using save_cwd/fchdir,
+ then readlink/restore_cwd. If either the save_cwd or the restore_cwd
+ fails, then give a diagnostic and exit nonzero. */
+
+# define AT_FUNC_NAME readlinkat
+# define AT_FUNC_F1 readlink
+# define AT_FUNC_POST_FILE_PARAM_DECLS , char *buf, size_t len
+# define AT_FUNC_POST_FILE_ARGS , buf, len
+# define AT_FUNC_RESULT ssize_t
+# include "at-func.c"
+# undef AT_FUNC_NAME
+# undef AT_FUNC_F1
+# undef AT_FUNC_POST_FILE_PARAM_DECLS
+# undef AT_FUNC_POST_FILE_ARGS
+# undef AT_FUNC_RESULT
+
+#endif