GETHOSTID(3) BSD Library Functions Manual GETHOSTID(3)NAME
gethostid, sethostid -- get/set unique identifier of current host
Standard C Library (libc, -lc)
The sethostid() function establishes a 32-bit identifier for the current processor that is intended to be unique among all UNIX systems in
existence. This 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 gethostid() 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).
SEE ALSO gethostname(3), sysctl(3), sysctl(8)HISTORY
The gethostid() and sethostid() syscalls appeared in 4.2BSD and were dropped in 4.4BSD.
32 bits for the identifier is too small.
BSD June 2, 1993 BSD
Check Out this Related Man Page
GETHOSTID(3) Linux Programmer's Manual GETHOSTID(3)NAME
gethostid, sethostid - get or set the unique identifier of the current host
int sethostid(long hostid);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sethostid(): _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
gethostid() and sethostid() respectively 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 geth-
ostbyname(3), and thus usually never needs to be set.
The sethostid() call is restricted to the superuser.
gethostid() returns the 32-bit identifier for the current host as set by sethostid().
On success, sethostid() returns 0; on error, -1 is returned, and errno is set to indicate the error.
sethostid() can fail with the following errors:
EACCES The caller did not have permission to write to the file used to store the host ID.
EPERM The calling process's effective user or group ID is not the same as its corresponding real ID.
4.2BSD; these functions were dropped in 4.4BSD. SVr4 includes gethostid() but not sethostid(). POSIX.1-2001 specifies gethostid() but not
In the glibc implementation, the hostid is stored in the file /etc/hostid. (In glibc versions before 2.2, the file /var/adm/hostid was
In the glibc implementation, if gethostid() cannot open the file containing the host ID, 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.)
It is impossible to ensure that the identifier is globally unique.
SEE ALSO hostid(1), gethostbyname(3)COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2009-01-13 GETHOSTID(3)