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/* Create a symlink relative to an open directory.
Copyright (C) 2009-2023 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>
#if HAVE_SYMLINKAT
# undef symlinkat
#include <fcntl.h>
#include <sys/stat.h>
#include <string.h>
/* Create a symlink, but reject trailing slash. */
int
rpl_symlinkat (char const *contents, int fd, char const *name)
{
size_t len = strlen (name);
if (len && name[len - 1] == '/')
{
struct stat st;
if (fstatat (fd, name, &st, AT_SYMLINK_NOFOLLOW) == 0
|| errno == EOVERFLOW)
errno = EEXIST;
return -1;
}
return symlinkat (contents, fd, name);
}
#elif !HAVE_SYMLINK
/* Mingw lacks symlink, and it is more efficient to provide a trivial
wrapper than to go through at-func.c to call rpl_symlink. */
int
symlinkat (_GL_UNUSED char const *path1, _GL_UNUSED int fd,
_GL_UNUSED char const *path2)
{
errno = ENOSYS;
return -1;
}
#else /* HAVE_SYMLINK */
/* Our openat helper functions expect the directory parameter first,
not second. These shims make life easier. */
/* Like symlink, but with arguments reversed. */
static int
symlink_reversed (char const *file, char const *contents)
{
return symlink (contents, file);
}
/* Like symlinkat, but with arguments reversed. */
static int
symlinkat_reversed (int fd, char const *file, char const *contents);
# define AT_FUNC_NAME symlinkat_reversed
# define AT_FUNC_F1 symlink_reversed
# define AT_FUNC_POST_FILE_PARAM_DECLS , char const *contents
# define AT_FUNC_POST_FILE_ARGS , contents
# 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
/* Create a symlink FILE, in the directory open on descriptor FD,
holding CONTENTS. If possible, do it without changing the
working directory. Otherwise, resort to using save_cwd/fchdir,
then symlink/restore_cwd. If either the save_cwd or the restore_cwd
fails, then give a diagnostic and exit nonzero. */
int
symlinkat (char const *contents, int fd, char const *file)
{
return symlinkat_reversed (fd, file, contents);
}
#endif /* HAVE_SYMLINK */
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