set-file-modes
set-file-modes is an interactive built-in function in `C source code
'.
(set-file-modes FILENAME MODE)
Set mode bits of file named FILENAME to MODE (an integer).
Only the 12 low bits of MODE are used.
Interactively, mode bits are read by `read-file-modes', which accepts
symbolic notation, like the `chmod' command from GNU Coreutils.