NAME "Net::LibResolv" - a Perl wrapper around libresolv SYNOPSIS use Net::LibResolv qw( res_query NS_C_IN NS_T_A $h_errno ); use Net::DNS::Packet; my $answer = res_query( "www.cpan.org", NS_C_IN, NS_T_A ); defined $answer or die "DNS failure - $h_errno\n"; foreach my $rr ( Net::DNS::Packet->new( \$answer )->answer ) { print $rr->string, "\n"; } DESCRIPTION The libresolv library provides functions to use the platform's standard DNS resolver to perform DNS queries. This Perl module provides a wrapping for the two primary functions, res_query(3) and res_search(3), allowing them to be used from Perl. The return value from each function is a byte buffer containing the actual DNS response packet. This will need to be parsed somehow to obtain the useful information out of it; most likely by using Net::DNS. FUNCTIONS $answer = res_query( $dname, $class, $type ) Calls the res_query(3) function on the given domain name, class and type number. Returns the answer byte buffer on success, or "undef" on failure. On failure sets the value of the $h_errno package variable. $dname should be a plain string. $class and $type should be numerical codes. See the "CONSTANTS" section for convenient definitions. $answer = res_search( $dname, $class, $type ) Calls the res_search(3) function on the given domain name, class and type number. Returns the answer byte buffer on success, or "undef" on failure. On failure sets the value of the $h_errno package variable. $dname should be a plain string. $class and $type should be numerical codes. See the "CONSTANTS" section for convenient definitions. VARIABLES $h_errno After an error from "res_query" or "res_search", this variable will be set to the error value, as a dual-valued scalar. Its numerical value will be one of the error constants (see below); it string value will be an error message version of the same (similar to the $! perl core variable). if( !defined( my $answer = res_query( ... ) ) ) { print "Try again later...\n" if $h_errno == TRY_AGAIN; } defined( my $answer = res_query( ... ) ) or die "Cannot res_query() - $h_errno\n"; CONSTANTS Class IDs The following set of constants define values for the $class parameter. Typically only "NS_C_IN" is actually used, for Internet. NS_C_IN NS_C_CHAOS NS_C_HS NS_C_INVALD NS_C_NONE NS_C_ANY $id = class_name2value( $name ) $name = class_value2name( $id ) Functions to convert between class names and ID values. Type IDs The following are examples of constants define values for the $type parameter. (They all follow the same naming pattern, named after the record type, so only a few are listed here.) NS_T_A NS_T_NS NS_T_CNAME NS_T_PTR NS_T_MX NS_T_TXT NS_T_SRV NS_T_AAAA NS_T_INVALID NS_T_ANY $id = type_name2value( $name ) $name = type_value2name( $id ) Functions to convert between type names and ID values. Errors The following constants define error values for $h_errno. HOST_NOT_FOUND NO_ADDRESS NO_DATA NO_RECOVERY TRY_AGAIN The values of "NO_ADDRESS" and "NO_DATA" may be the same. SEE ALSO * Net::DNS - Perl interface to the DNS resolver AUTHOR Paul Evans