gethostbyname_r Subroutine

Purpose

Gets network host entry by name.

Library

Standard C Library (libc.a)
(libbind)
(libnis)
(liblocal)

Syntax

#include netdb.h>
int gethostbyname_r(Name, Htent, Ht_data)

const char *Name, struct hostent *Htent, struct hostent_data *Ht_data;

Description

This function internally calls the gethostbyname subroutine and stores the value returned by the gethostbyname subroutine to the hostent structure.

Parameters

Item	Description
Name	Points to the host name (which is a constant).
Htent	Points to a hostent structure in which the return value of the gethostbyname subroutine is stored.
Ht_data	Points to a hostent_data structure.

Return Values

The function returns a 0 if successful and a -1 if unsuccessful.

Note:

The return value of the gethostbyname subroutine points to static data that is overwritten by subsequent calls. This data must be copied at every call to be saved for use by subsequent calls. The gethostbyname_r subroutine solves this problem.

If the Name parameter is an IP address, this subroutine searches for a machine with that IP address as a name. Because of this, use the gethostbyaddr_r subroutine instead of the gethostbyname_r subroutine if the Name parameter is an IP address.

Error Codes

The gethostbyname_r subroutine is unsuccessful if any of the following errors occurs:

Item	Description
HOST_NOT_FOUND	The host specified by the Name parameter was not found.
TRY_AGAIN	The local server did not receive a response from an authoritative server. Try again later.
NO_RECOVERY	An unrecoverable error occurred.
NO_ADDRESS	The requested Name is valid but does not have an Internet address at the name server.
SERVICE_UNAVAILABLE	None of the name services specified are running or available.
EINVAL	The hostent pointer is NULL.

Files

Item	Description
/etc/hosts	Contains the host name data base.
/etc/resolv.conf	Contains the name server and domain name.
/etc/netsvc.conf	Contains the name services ordering.
/usr/include/netdb.h	Contains the network database structure.