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   gethostid    ( 3 )

получить или установить уникальный идентификатор текущего хоста (get or set the unique identifier of the current host)

Имя (Name)

gethostid, sethostid - get or set the unique identifier of the
       current host

Синопсис (Synopsis)

#include <unistd.h>

long gethostid(void); int sethostid(long hostid);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

gethostid(): Since glibc 2.20: _DEFAULT_SOURCE || _XOPEN_SOURCE >= 500 Up to and including glibc 2.19: _BSD_SOURCE || _XOPEN_SOURCE >= 500

sethostid(): Since glibc 2.21: _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)


Описание (Description)

gethostid() and sethostid() respectively get or set a unique
       32-bit identifier for the current machine.  The 32-bit identifier
       was 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.


Возвращаемое значение (Return value)

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.


Ошибки (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.


Атрибуты (Attributes)

For an explanation of the terms used in this section, see
       attributes(7).

┌────────────┬───────────────┬───────────────────────────────────┐ │Interface Attribute Value │ ├────────────┼───────────────┼───────────────────────────────────┤ │gethostid() │ Thread safety │ MT-Safe hostid env locale │ ├────────────┼───────────────┼───────────────────────────────────┤ │sethostid() │ Thread safety │ MT-Unsafe const:hostid │ └────────────┴───────────────┴───────────────────────────────────┘


Стандарты (Conforming to)

4.2BSD; these functions were dropped in 4.4BSD.  SVr4 includes
       gethostid() but not sethostid().

POSIX.1-2001 and POSIX.1-2008 specify gethostid() but not sethostid().


Примечание (Note)

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 used.)

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.)


Ошибки (баги) (Bugs)

It is impossible to ensure that the identifier is globally
       unique.

Смотри также (See also)

hostid(1), gethostbyname(3)