/usr/include/x86_64-linux-gnu/sys/termios.h is in libc6-dev 2.23-0ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | #ifndef _SYS_TERMIOS_H
#define _SYS_TERMIOS_H
#include <termios.h>
#endif
|