/usr/include/lastlog.h is in libc6-dev 2.13-38+deb7u10.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | /* This header file is used in 4.3BSD to define `struct lastlog',
which we define in <bits/utmp.h>. */
#include <utmp.h>
|