Provided by: manpages-dev_3.15-1_all
gethostid, sethostid - get or set the unique identifier of the current
int sethostid(long hostid);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sethostid(): _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
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.
gethostid() returns the 32-bit identifier for the current host as set
4.2BSD; these functions were dropped in 4.4BSD. SVr4 includes
gethostid() but not sethostid(). POSIX.1-2001 specifies gethostid()
but not sethostid().
In the glibc implementation, if gethostid() cannot open /etc/hostid,
then it obtains the hostname using gethostname(2), passes that hostname
to gethostbyname_r(3) in order to obtain the host’s IPv4 address, and
returns a value obtained by bit-twiddling the IPv4 address. (This
value may not be unique.)
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