gethostid - get the unique identifier of the current host
long int gethostid(void);
Get the unique 32-bit identifier for the current machine. The 32-bit identifier is intended to be unique among all UNIX systems in existence. This normally resembles the Internet address for the local machine, as returned by gethostbyname(3), and thus usually never needs to be set with the sethostid(2) call.
The hostid is often used by programs for licensing matters.
The hostid argument is often stored in the file /etc/hostid.
gethostid(2) returns the 32-bit identifier for the current host as set by sethostid(2).
4.2BSD. These functions were dropped in 4.4BSD. POSIX.1 does not define these functions, but ISO/IEC 9945-1:1990 mentions
them in B.4.4.1. SVr4 includes gethostid(2) but not sethostid(2).