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.

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.

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.

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_ninit Subroutine, res_query subroutine, res_send subroutine.

Sockets Overview and Understanding Domain Name Resolution in AIX 5L Version 5.2 Communications Programming Concepts.