dnsquery − query domain name servers using resolver

dnsquery [−n nameserver] [−t type] [−c class] [−r retry] [−p period] [−d] [−s] [−v] host

DESCRIPTION

The dnsquery program is a general interface to nameservers via BIND resolver library calls. The program supports queries to the nameserver with an opcode of QUERY. This program is intended to be a replacement or supplement to programs like nstest, nsquery and nslookup. All arguments except for host and nameserver are treated without case-sensitivity.

The nameserver to be used in the query. Nameservers can appear as either Internet addresses of the form w.x.y.z or can appear as domain names. (Default: as specified in /etc/resolv.conf.)

−t type’ The type of resource record of interest. Types include:
A’ address
NS’ nameserver
CNAME’ canonical name

HINFO’ host information
MINFO’ mailbox information

DCE or AFS server

Note that any case may be used. (Default: ANY.)

−c class’ The class of resource records of interest. Classes include:

’ Internet

CHAOS’ Chaos

Note that any case may be used. (Default: IN.)

−r retry’ The number of times to retry if the nameserver is not responding. (Default: 4.)

−p period
Period to wait before timing out. (Default: RES_TIMEOUT.)

−d’ Turn on debugging. This sets the RES_DEBUG bit of the resolver’s options field. (Default: no debugging.)

−s’ Use a stream rather than a packet. This uses a TCP stream connection with the nameserver rather than a UDP datagram. This sets the RES_USEVC bit of the resolver’s options field. (Default: UDP datagram.)

−v’ Synonym for the ‘‘−s’’ flag.

host’ The name of the host (or domain) of interest.

FILES

<arpa/nameser.h>
list of usable RR types and classes
<resolv.h>
list of resolver flags

DIAGNOSTICS

If the resolver fails to answer the query and debugging has not been turned on, dnsquery will simply print a message like:

Query failed (rc = 1): Unknown host

The value of the return code is supplied by h_errno.

nslookup(8), nstest(1), nsquery(1), named(8), resolver(5).

Bryan Beecher

Queries of a class other than IN can have interesting results since ordinarily a nameserver only has a list of root nameservers for class IN resource records.

Dnsquery uses a call to inet_addr() to determine if the argument for the ‘‘−n’’ option is a valid Internet address. Unfortunately, inet_addr() seems to cause a segmentation fault with some (bad) IP addresses (e.g., 1.2.3.4.5).

4th Berkeley Distribution March 10, 1990 4th Berkeley Distribution