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Technical Reference: Communications, Volume 2


res_search Subroutine

Purpose

Makes a query and awaits a response.

Library

Standard C Library (libc.a)

Syntax

#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>


int res_search (DomName, Class, Type, Answer, AnswerLength)
char * DomName;
int Class;
int Type;
u_char * Answer;
int AnswerLength;

Description

The res_search subroutine makes a query and awaits a response like the res_query subroutine. However, it also implements the default and search rules controlled by the RES_DEFNAMES and RES_DNSRCH options.

The res_search subroutine is one of a set of subroutines that form the resolver, a set of functions that resolve domain names. The _res data structure contains global information used by the resolver subroutines. The /usr/include/resolv.h file contains the _res structure definition.

Parameters


DomName Points to the name of the domain. If the DomName parameter points to a single-component name and the RES_DEFNAMES structure is set, as it is by default, the subroutine appends the default domain name to the single-component name. The current domain name is defined by the name server in use or is specified in the /etc/resolv.conf file.

If the RES_DNSRCH bit is set, as it is by default, the res_search subroutine searches for host names in both the current domain and in parent domains.

Class Specifies one of the following values:

C_IN
Specifies the ARPA Internet.

C_CHAOS
Specifies the Chaos network at MIT.
Type Requires one of the following values:

T_A
Host address

T_NS
Authoritative server

T_MD
Mail destination

T_MF
Mail forwarder

T_CNAME
Canonical name

T_SOA
Start-of-authority zone

T_MB
Mailbox-domain name

T_MG
Mail-group member

T_MR
Mail-rename name

T_NULL
Null resource record

T_WKS
Well-known service

T_PTR
Domain name pointer

T_HINFO
Host information

T_MINFO
Mailbox information

T_MX
Mail-routing information

T_UINFO
User (finger command) information

T_UID
User ID

T_GID
Group ID
Answer Points to an address where the response is stored.
AnswerLength Specifies the size of the answer buffer.

Return Values

Upon successful completion, the res_search subroutine returns the size of the response. Upon unsuccessful completion, the res_search subroutine returns a value of -1 and sets the h_errno value to the appropriate error.

Implementation Specifics

The res_search subroutine is part of Base Operating System (BOS) Runtime.

All applications containing the res_search subroutine must be compiled with _BSD set to a specific value. Acceptable values are 43 and 44. In addition, all socket applications must include the BSD libbsd.a library.

Files


/etc/resolv.conf
                          Contains the name server and domain name.

Related Information

The finger command.

The dn_comp subroutine, dn_expand subroutine, _getlong subroutine, _getshort subroutine, putlong subroutine, putshort subroutine, res_init subroutine, res_mkquery subroutine, res_query subroutine, res_send subroutine.

Sockets Overview and Understanding Domain Name Resolution in AIX 5L Version 5.1 Communications Programming Concepts.


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