res_query()

Query the local Internet domain name server

Synopsis:

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

int res_query( const char * dname, 
               int class, 
               int type,
               u_char * answer, 
               int anslen );

The res_query() function provides an interface to the server query mechanism. It constructs a query, sends it to the local server, waits for a response, and makes preliminary checks on the reply. The query requests information of the specified type and class for the specified fully qualified domain name dname. The reply message is left in the answer buffer with length anslen supplied by the caller.

The resolver routines are used for making, sending, and interpreting query and reply messages with Internet domain name servers. Global configuration and state information used by the resolver routines is kept in the structure _res. For more information on the options, see res_init().

The res_query() function uses the following lower-level routines:

res_mkquery() constructs a standard query message.
res_send() sends the preformatted query and returns an answer.
dn_comp() compresses a domain name.
dn_expand() expands the compressed domain name to a full domain name.

/etc/resolv.conf: Resolver configuration file.

Environment variables:

LOCALDOMAIN: When set, LOCALDOMAIN contains a domain name that overrides the current domain name.

Classification:

Unix

Safety:
Interrupt handler	No
Signal handler	No
Thread	No

res_query()

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