(fchmodat): New file and function.

1 files changed, 104 insertions, 0 deletions

diff --git a/lib/fchmodat.c b/lib/fchmodat.c
new file mode 100644
index 000000000..f8e84534a
--- /dev/null
+++ b/lib/fchmodat.c
@@ -0,0 +1,104 @@
+/* Change the protections of file relative to an open directory.
+   Copyright (C) 2006 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 2, 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, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* written by Jim Meyering */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "openat.h"
+
+#include <errno.h>
+
+#include "dirname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
+#include "save-cwd.h"
+
+#include "gettext.h"
+#define _(msgid) gettext (msgid)
+
+#include "openat-priv.h"
+
+/* Some systems don't have ENOSYS.  */
+#ifndef ENOSYS
+# ifdef ENOTSUP
+#  define ENOSYS ENOTSUP
+# else
+/* Some systems don't have ENOTSUP either.  */
+#  define ENOSYS EINVAL
+# endif
+#endif
+
+#ifndef HAVE_LCHMOD
+# undef lchmod
+# define lchmod(f,m) (errno = ENOSYS, -1)
+#endif
+
+/* Solaris 10 has no function like this.
+   Invoke chmod or lchmod on file, FILE, using mode MODE, in the directory
+   open on descriptor FD.  If possible, do it without changing the
+   working directory.  Otherwise, resort to using save_cwd/fchdir,
+   then mkdir/restore_cwd.  If either the save_cwd or the restore_cwd
+   fails, then give a diagnostic and exit nonzero.
+   Note that an attempt to use a FLAG value of AT_SYMLINK_NOFOLLOW
+   on a system without lchmod support causes this function to fail.  */
+int
+fchmodat (int fd, char const *file, mode_t mode, int flag)
+{
+  struct saved_cwd saved_cwd;
+  int saved_errno;
+  int err;
+
+  if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
+    return (flag == AT_SYMLINK_NOFOLLOW
+	    ? lchmod (file, mode)
+	    : chmod (file, mode));
+
+  {
+    char *proc_file;
+    BUILD_PROC_NAME (proc_file, fd, file);
+    err = (flag == AT_SYMLINK_NOFOLLOW
+	   ? lchmod (proc_file, mode)
+	   : chmod (proc_file, mode));
+    /* If the syscall succeeds, or if it fails with an unexpected
+       errno value, then return right away.  Otherwise, fall through
+       and resort to using save_cwd/restore_cwd.  */
+    if (0 <= err || ! EXPECTED_ERRNO (errno))
+      return err;
+  }
+
+  if (save_cwd (&saved_cwd) != 0)
+    openat_save_fail (errno);
+
+  err = fchdir (fd);
+  saved_errno = errno;
+
+  if (! err)
+    {
+      err = (flag == AT_SYMLINK_NOFOLLOW
+	     ? lchmod (file, mode)
+	     : chmod (file, mode));
+      saved_errno = errno;
+
+      if (restore_cwd (&saved_cwd) != 0)
+	openat_restore_fail (errno);
+    }
+
+  free_cwd (&saved_cwd);
+  errno = saved_errno;
+  return err;
+}