Table of Contentsdnsquery - query domain name servers using resolver
dnsquery [-n nameserver] [-t type] [-c class] [-r retry][-p retry period] [-d] [-s] [-v] host
The dnsquery program is a general interface to nameserversvia BIND resolver library calls. The program supportsqueries to the nameserver with an opcode of QUERY. Thisprogram is intended to be a replacement or supplement toprograms like nstest, nsquery and nslookup. All argumentsexcept for host and ns are treated without casesensitivity.
- -n
- The nameserver to be used in the query. Nameserverscan appear as either Internet addressesof the form w.x.y.z or can appear as domainnames. (default: as specified in/etc/resolv.conf)
- -t
- The type of resource record of interest. Typesinclude:
- A
- address
- NS
- nameserver
- CNAME
- canonical name
- PTR
- domain name pointer
- SOA
- start of authority
- WKS
- well-known service
- HINFO
- host information
- MINFO
- mailbox information
- MX
- mail exchange
- RP
- responsible person
- MG
- mail group memberAFSDBDCE or AFS server
- ANY
- wildcard
Note that any case may be used. (default: ANY)
- -c
- The class of resource records of interest.Classes include:
- IN
- Internet
- HS
- Hesiod
- CHAOS
- Chaos
- ANY
- wildcard
Note that any case may be used. (default: IN)
- -r
- The number of times to retry if the nameserver
is not responding. (default: 4)
- -p
- Period to wait before timing out. (default:RES_TIMEOUT) options field. (default: anyanswer)
- -d
- Turn on debugging. This sets the RES_DEBUG bitof the resolver's options field. (default: nodebugging)
- -s
- Use a stream rather than a packet. This uses aTCP stream connection with the nameserver ratherthan a UDP datagram. This sets the RES_USEVCbit of the resolver's options field. (default:UDP)
- -v
- Synonym for the `s' flag.
- host
- The name of the host (or domain) of interest.
- /etc/resolv.conf
- to get the default ns and search lists
- <arpa/nameser.h>
- list of usable RR types and classes
- <resolv.h>
- list of resolver flags
nslookup(8), nstest(1), nsquery(1), named(8), resolver(5)
If the resolver fails to answer the query and debugginghas not been turned on, dnsquery will simply print a messagelike:
Query failed (rc = 1) : Unknown host
The value of the return code is supplied by h_errno.
Queries of a class other than IN can have interestingresults since ordinarily a nameserver only has a list ofroot nameservers for class IN resource records.
Query uses a call to inet_addr() to determine if the argumentfor the `-n' option is a valid Internet address.Unfortunately, inet_addr() seems to cause a segmentationfault with some (bad) addresses (e.g. 1.2.3.4.5).
Bryan Beecher
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