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res_search(3)


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_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) information

      T_UID   User ID

      T_GID   Group 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).

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