102 lines
2.8 KiB
C
102 lines
2.8 KiB
C
/* Create a symlink relative to an open directory.
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Copyright (C) 2009-2022 Free Software 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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/* written by Eric Blake */
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#include <config.h>
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/* Specification. */
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#include <unistd.h>
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#include <errno.h>
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#include <stdlib.h>
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#if HAVE_SYMLINKAT
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# undef symlinkat
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#include <fcntl.h>
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#include <sys/stat.h>
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#include <string.h>
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/* Create a symlink, but reject trailing slash. */
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int
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rpl_symlinkat (char const *contents, int fd, char const *name)
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{
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size_t len = strlen (name);
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if (len && name[len - 1] == '/')
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{
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struct stat st;
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if (fstatat (fd, name, &st, AT_SYMLINK_NOFOLLOW) == 0
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|| errno == EOVERFLOW)
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errno = EEXIST;
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return -1;
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}
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return symlinkat (contents, fd, name);
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}
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#elif !HAVE_SYMLINK
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/* Mingw lacks symlink, and it is more efficient to provide a trivial
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wrapper than to go through at-func.c to call rpl_symlink. */
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int
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symlinkat (_GL_UNUSED char const *path1, _GL_UNUSED int fd,
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_GL_UNUSED char const *path2)
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{
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errno = ENOSYS;
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return -1;
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}
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#else /* HAVE_SYMLINK */
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/* Our openat helper functions expect the directory parameter first,
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not second. These shims make life easier. */
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/* Like symlink, but with arguments reversed. */
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static int
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symlink_reversed (char const *file, char const *contents)
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{
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return symlink (contents, file);
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}
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/* Like symlinkat, but with arguments reversed. */
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static int
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symlinkat_reversed (int fd, char const *file, char const *contents);
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# define AT_FUNC_NAME symlinkat_reversed
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# define AT_FUNC_F1 symlink_reversed
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# define AT_FUNC_POST_FILE_PARAM_DECLS , char const *contents
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# define AT_FUNC_POST_FILE_ARGS , contents
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# include "at-func.c"
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# undef AT_FUNC_NAME
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# undef AT_FUNC_F1
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# undef AT_FUNC_POST_FILE_PARAM_DECLS
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# undef AT_FUNC_POST_FILE_ARGS
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/* Create a symlink FILE, in the directory open on descriptor FD,
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holding CONTENTS. If possible, do it without changing the
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working directory. Otherwise, resort to using save_cwd/fchdir,
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then symlink/restore_cwd. If either the save_cwd or the restore_cwd
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fails, then give a diagnostic and exit nonzero. */
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int
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symlinkat (char const *contents, int fd, char const *file)
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{
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return symlinkat_reversed (fd, file, contents);
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}
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#endif /* HAVE_SYMLINK */
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