.\" %%%LICENSE_END
.\"
.\" Modified Tue Oct 22 00:22:35 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
-.TH GETHOSTID 3 2015-05-07 "Linux" "Linux Programmer's Manual"
+.TH GETHOSTID 3 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
gethostid, sethostid \- get or set the unique identifier of the current host
.SH SYNOPSIS
.B #include <unistd.h>
-.sp
+.PP
.B long gethostid(void);
.br
.BI "int sethostid(long " hostid );
-.sp
+.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
-.sp
+.PP
.ad l
.br
.BR gethostid ():
.RS 4
-_BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
-_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
+_BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500
+.\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
.RE
.BR sethostid ():
-.RS 4
-_BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE\ <\ 500)
-.RE
+.nf
+ Since glibc 2.21:
+.\" commit 266865c0e7b79d4196e2cc393693463f03c90bd8
+ _DEFAULT_SOURCE
+ In glibc 2.19 and 2.20:
+ _DEFAULT_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE\ <\ 500)
+ Up to and including glibc 2.19:
+ _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE\ <\ 500)
+.fi
.ad b
.SH DESCRIPTION
.BR gethostid ()
machine, as returned by
.BR gethostbyname (3),
and thus usually never needs to be set.
-
+.PP
The
.BR sethostid ()
call is restricted to the superuser.
.BR gethostid ()
returns the 32-bit identifier for the current host as set by
.BR sethostid ().
-
+.PP
On success,
.BR sethostid ()
returns 0; on error, \-1 is returned, and
.BR sethostid ()
T} Thread safety MT-Unsafe const:hostid
.TE
-
+.sp 1
.SH CONFORMING TO
4.2BSD; these functions were dropped in 4.4BSD.
SVr4 includes
.BR gethostid ()
but not
.BR sethostid ().
-
+.PP
POSIX.1-2001 and POSIX.1-2008 specify
.BR gethostid ()
but not
.I /var/adm/hostid
was used.)
.\" libc5 used /etc/hostid; libc4 didn't have these functions
-
+.PP
In the glibc implementation, if
.BR gethostid ()
cannot open the file containing the host ID,