NAME

res_search, res_query − Query a domain server and check the response

SYNOPSIS

#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h> int res_search(
        const char ∗domain_name,
        int class,
        int type,
        u_char ∗answer,
        int answer_len );

The res_query() syntax is as follows: int res_query(
        const char ∗domain_name,
        int class,
        int type,
        u_char ∗answer,
        int answer_len );

LIBRARY

Standard C Library (libc)

PARAMETERS

domain_name
Points to the fully-qualified name of the domain.  If the domain_name parameter points to a single label and the RES_DEFNAMES bit is set, as it is by default, the function appends domain_name to the current domain name.  The current domain name is defined by the name server in use or in the /etc/resolv.conf file. 

class
Specifies one of the following parameters:

C_INSpecifies the ARPA Internet. 

C_CHAOS
Specifies the Chaos network at MIT.

typeRequires one of the following values:

T_AHost address

T_NSAuthoritative server

T_MDMail destination

T_MFMail forwarder

T_CNAME
Canonical name

T_SOAStart of authority zone

T_MBMailbox domain name

T_MGMail group member

T_MRMail rename name

T_NULL
NULL resource record

T_WKSWell known service

T_PTRDomain name pointer

T_HINFO
Host information

T_MINFO
Mailbox information

T_MXMail routing information

T_UINFO
User (finger) information

T_UIDUser ID

T_GIDGroup ID

answer
Points to a location of the server’s reply.

answer_len
Specifies the length of the answer pointed to by the answer parameter. 

DESCRIPTION

The res_search() and res_query() functions construct a query, send it to the local server, and await a response.  In addition, res_search() implements the default and search rules specified by the RES_DEFNAMES and RES_DNSRCH resolver options.  The function returns the first successful reply. 

The res_search() and res_query() functions part of a set of subroutines that form the resolver, a set of functions that resolve domain names.  Global information that is used by the resolver functions is kept in the _res data structure. The /include/resolv.h file contains the _res data structure definition. 

RETURN VALUES

Upon successful completion, the res_search() function returns the size of the answer. If the answer is larger than the value of the answer_len parameter, the function fails and returns a value of -1. 

ERRORS

If an error occurs during a resolver operation, the h_errno external variable is set.  Error code values and reasons are defined in <netdb.h>. 

FILES

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

SEE ALSO

Functions: dn_comp(3), dn_expand(3), dn_find(3), dn_skipname(3), _getlong(3), _getshort(3), putlong(3), putshort(3), res_init(3), res_mkquery(3), res_query(3), res_send(3).