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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 17:39:29 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 17:39:29 +0000 |
commit | 8ffec2a3aba6f114784e11f89ef1d57a096ae540 (patch) | |
tree | ccebcbad06203e8241a8e7249f8e6c478a3682ea /lib/readlinkat.c | |
parent | Initial commit. (diff) | |
download | coreutils-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.c | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/lib/readlinkat.c b/lib/readlinkat.c new file mode 100644 index 0000000..68ec65e --- /dev/null +++ b/lib/readlinkat.c @@ -0,0 +1,82 @@ +/* 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 |