Searches for a default domain name and Internet address.
#include <sys/types.h> #include <netinet/in.h> #include <arpa/nameser.h> #include <resolv.h> void res_init ( )
The res_init subroutine reads the /etc/resolv.conf file for the default domain name and the Internet address of the initial hosts running the name server.
Note: If the /etc/resolv.conf file does not exist, the res_init subroutine attempts name resolution using the local /etc/hosts file. If the system is not using a domain name server, the /etc/resolv.conf file should not exist. The /etc/hosts file should be present on the system even if the system is using a name server. In this instance, the file should contain the host IDs that the system requires to function even if the name server is not functioning.
The res_init subroutine is one of a set of subroutines that form the resolver, a set of functions that translate domain names to Internet addresses. All resolver subroutines use the /usr/include/resolv.h file, which defines the _res structure. The res_init subroutine stores domain name information in the _res structure. Three environment variables, LOCALDOMAIN, RES_TIMEOUT, and RES_RETRY, affect default values related to the _res structure.
For more information on the _res structure, see "Understanding Domain Name Resolution" in AIX Version 4.3 Communications Programming Concepts.
The res_init subroutine is part of Base Operating System (BOS) Runtime.
All applications containing the res_init 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.
| /etc/resolv.conf | |
| Contains the name server and domain name. | |
| /etc/hosts | |
| Contains host names and their addresses for hosts in a network. This file is used to resolve a host name into an Internet address. | |
The dn_comp subroutine, dn_expand subroutine, _getlong subroutine, _getshort subroutine, putlong subroutine, putshort subroutine, res_mkquery subroutine, res_query subroutine, res_search subroutine, res_send subroutine.
Sockets Overview and Understanding Domain Name Resolution in AIX Version 4.3 Communications Programming Concepts.