res_search(3) [osf1 man page]
res_search(3) Library Functions Manual res_search(3) NAME
res_search, res_query - Queries domain server and checks response LIBRARY
Standard C Library (libc.a, libc.so) 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;) PARAMETERS
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. Specifies one of the following parameters: Specifies the ARPA Internet. Specifies the Chaos network at MIT. Requires one of the following values: Host address Authoritative server Mail destination Mail forwarder Canonical name Start of authority zone Mailbox domain name Mail group member Mail rename name NULL resource record Well known service Domain name pointer Host information Mailbox information Mail routing information User (finger) information User ID Group ID Points to a location of the server's reply. 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 suc- cessful 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
Contains the name server and domain name. RELATED INFORMATION
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). delim off res_search(3)
Check Out this Related Man Page
RESOLVER(3) Linux Programmer's Manual RESOLVER(3) NAME
res_init, res_query, res_search, res_querydomain, res_mkquery, res_send, dn_comp, dn_expand - resolver routines SYNOPSIS
#include <netinet/in.h> #include <arpa/nameser.h> #include <resolv.h> extern struct state _res; int res_init(void); int res_query(const char *dname, int class, int type, unsigned char *answer, int anslen); int res_search(const char *dname, int class, int type, unsigned char *answer, int anslen); int res_querydomain(const char *name, const char *domain, int class, int type, unsigned char *answer, int anslen); int res_mkquery(int op, const char *dname, int class, int type, char *data, int datalen, struct rrec *newrr, char *buf, int buflen); int res_send(const char *msg, int msglen, char *answer, int anslen); int dn_comp(unsigned char *exp_dn, unsigned char *comp_dn, int length, unsigned char **dnptrs, unsigned char *exp_dn, unsigned char **lastdnptr); int dn_expand(unsigned char *msg, unsigned char *eomorig, unsigned char *comp_dn, unsigned char *exp_dn, int length); DESCRIPTION
These functions make queries to and interpret the responses from Internet domain name servers. The res_init() function reads the configuration files (see resolv+(8)) to get the default domain name, search order and name server address(es). If no server is given, the local host is tried. If no domain is given, that associated with the local host is used. It can be overridden with the environment variable LOCALDOMAIN. res_init() is normally executed by the first call to one of the other functions. The res_query() function queries the name server for the fully-qualified domain name name of specified type and class. The reply is left in the buffer answer of length anslen supplied by the caller. The res_search() function makes a query and waits for the response like res_query(), but in addition implements the default and search rules controlled by RES_DEFNAMES and RES_DNSRCH (see description of _res options below). The res_querydomain() function makes a query using res_query() on the concatenation of name and domain. The following functions are lower-level routines used by res_query(). The res_mkquery() function constructs a query message in buf of length buflen for the domain name dname. The query type op is usually QUERY, but can be any of the types defined in <arpa/nameser.h>. newrr is currently unused. The res_send() function sends a pre-formatted query given in msg of length msglen and returns the answer in answer which is of length anslen. It will call res_init(), if it has not already been called. The dn_comp() function compresses the domain name exp_dn and stores it in the buffer comp_dn of length length. The compression uses an array of pointers dnptrs to previously compressed names in the current message. The first pointer points to the beginning of the message and the list ends with NULL. The limit of the array is specified by lastdnptr. if dnptr is NULL, domain names are not compressed. If lastdnptr is NULL, the list of labels is not updated. The dn_expand() function expands the compressed domain name comp_dn to a full domain name, which is placed in the buffer exp_dn of size length. The compressed name is contained in a query or reply message, and msg points to the beginning of the message. The resolver routines use global configuration and state information contained in the structure _res, which is defined in <resolv.h>. The only field that is normally manipulated by the user is _res.options. This field can contain the bitwise ``or'' of the following options: RES_INIT True if res_init() has been called. RES_DEBUG Print debugging messages. RES_AAONLY Accept authoritative answers only. res_send() continues until it fins an authoritative answer or returns an error. [Not currently implemented]. RES_USEVC Use TCP connections for queries rather than UDP datagrams. RES_PRIMARY Query primary domain name server only. RES_IGNTC Ignore truncation errors. Don't retry with TCP. [Not currently implemented]. RES_RECURSE Set the recursion desired bit in queries. Recursion is carried out by the domain name server, not by res_send(). [Enabled by default]. RES_DEFNAMES If set, res_search() will append the default domain name to single component names, ie. those that do not contain a dot. [Enabled by default]. RES_STAYOPEN Used with RES_USEVC to keep the TCP connection open between queries. RES_DNSRCH If set, res_search() will search for host names in the current domain and in parent domains. This option is used by gethostby- name(3). [Enabled by default]. RETURN VALUE
The res_init() function returns 0 on success, or -1 if an error occurs. The res_query(), res_search(), res_querydomain(), res_mkquery() and res_send() functions return the length of the response, or -1 if an error occurs. The dn_comp() and dn_expand() functions return the length of the compressed name, or -1 if an error occurs. FILES
/etc/resolv.conf resolver configuration file /etc/host.conf resolver configuration file CONFORMING TO
BSD 4.3 SEE ALSO
gethostbyname(3), hostname(7), named(8), resolv+(8) BSD
1993-05-21 RESOLVER(3)