#include <unistd.h> long gethostid(void); int sethostid(long hostid);
描述Get or set a 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.
The sethostid() call is restricted to the superuser.
The hostid argument is stored in the file /etc/hostid.
返回值gethostid() returns the 32-bit identifier for the current host as set by sethostid(2).
遵循于4.2BSD; these functions were dropped in 4.4BSD. SVr4 includes gethostid() but notsethostid(). POSIX.1-2001 specifies gethostid() but not sethostid().
id = gethostid (); /* This is a no-op unless unsigned int is wider than 32 bits. */ id &= 0xffffffff;