GETHOSTID(3) Library Functions Manual GETHOSTID(3)

gethostid, sethostid — get/set unique identifier of current host

Standard C Library (libc, -lc)

#include <unistd.h>

long
gethostid(void);

void
sethostid(long hostid);

The () function establishes a 32-bit identifier for the current processor. The id, intended to be unique among all UNIX systems in existence, is normally a DARPA Internet address for the local machine. This call is allowed only to the super-user and is normally performed at boot time.

The () function returns the 32-bit identifier for the current processor.

This function has been deprecated. The hostid should be set or retrieved by use of sysctl(3).

gethostname(3), sysctl(3), sysctl(8)

The gethostid() and sethostid() syscalls appeared in 4.2BSD and were dropped in 4.4BSD.

32 bits for the identifier is too small.

June 2, 1993 macOS 15.2