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/* Implement lchmod on platforms where it does not work correctly.
Copyright 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 Paul Eggert */
#include <config.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <intprops.h>
/* Work like lchmod, except when FILE is a symbolic link.
In that case, set errno to EOPNOTSUPP and return -1. */
int
lchmod (char const *file, mode_t mode)
{
#if HAVE_FCHMODAT
return fchmodat (AT_FDCWD, file, mode, AT_SYMLINK_NOFOLLOW);
#elif defined O_PATH && defined AT_FDCWD
int fd = openat (AT_FDCWD, file, O_PATH | O_NOFOLLOW | O_CLOEXEC);
if (fd < 0)
return fd;
static char const fmt[] = "/proc/self/fd/%d";
char buf[sizeof fmt - sizeof "%d" + INT_BUFSIZE_BOUND (int)];
sprintf (buf, fmt, fd);
int chmod_result = chmod (buf, mode);
int chmod_errno = errno;
close (fd);
if (chmod_result == 0)
return chmod_result;
if (chmod_errno != ENOENT)
{
errno = chmod_errno;
return chmod_result;
}
/* /proc is not mounted; fall back on racy implementation. */
#endif
#if HAVE_LSTAT
struct stat st;
int lstat_result = lstat (file, &st);
if (lstat_result != 0)
return lstat_result;
if (S_ISLNK (st.st_mode))
{
errno = EOPNOTSUPP;
return -1;
}
#endif
return chmod (file, mode);
}
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