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host – DNS lookup utility


host [-aCdlnrsTwv] [-c class] [-N ndots] [-R number] [-t type] [-W wait] [-m flag] [-4] [-6] [-v] [-V] {name} [server]


host is a simple utility for performing DNS lookups. It is normally
used to convert names to IP addresses and vice versa. When no arguments
or options are given, host prints a short summary of its command line
arguments and options.

name is the domain name that is to be looked up. It can also be a
dotted-decimal IPv4 address or a colon-delimited IPv6 address, in which
case host will by default perform a reverse lookup for that address.
server is an optional argument which is either the name or IP address
of the name server that host should query instead of the server or
servers listed in /etc/resolv.conf.

The -a (all) option is equivalent to setting the -v option and asking
host to make a query of type ANY.

When the -C option is used, host will attempt to display the SOA
records for zone name from all the listed authoritative name servers
for that zone. The list of name servers is defined by the NS records
that are found for the zone.

The -c option instructs to make a DNS query of class class. This can be
used to lookup Hesiod or Chaosnet class resource records. The default
class is IN (Internet).

Verbose output is generated by host when the -d or -v option is used.
The two options are equivalent. They have been provided for backwards
compatibility. In previous versions, the -d option switched on
debugging traces and -v enabled verbose output.

List mode is selected by the -l option. This makes host perform a zone
transfer for zone name. Transfer the zone printing out the NS, PTR and
address records (A/AAAA). If combined with -a all records will be

The -i option specifies that reverse lookups of IPv6 addresses should
use the IP6.INT domain as defined in RFC1886. The default is to use

The -N option sets the number of dots that have to be in name for it to
be considered absolute. The default value is that defined using the
ndots statement in /etc/resolv.conf, or 1 if no ndots statement is
present. Names with fewer dots are interpreted as relative names and
will be searched for in the domains listed in the search or domain
directive in /etc/resolv.conf.

The number of UDP retries for a lookup can be changed with the -R
option. number indicates how many times host will repeat a query that
does not get answered. The default number of retries is 1. If number is
negative or zero, the number of retries will default to 1.

Non-recursive queries can be made via the -r option. Setting this
option clears the RD — recursion desired — bit in the query which host
makes. This should mean that the name server receiving the query will
not attempt to resolve name. The -r option enables host to mimic the
behavior of a name server by making non-recursive queries and expecting
to receive answers to those queries that are usually referrals to other
name servers.

By default, host uses UDP when making queries. The -T option makes it
use a TCP connection when querying the name server. TCP will be
automatically selected for queries that require it, such as zone
transfer (AXFR) requests.

The -4 option forces host to only use IPv4 query transport. The -6
option forces host to only use IPv6 query transport.

The -t option is used to select the query type. type can be any
recognized query type: CNAME, NS, SOA, SIG, KEY, AXFR, etc. When no
query type is specified, host automatically selects an appropriate
query type. By default, it looks for A, AAAA, and MX records, but if
the -C option was given, queries will be made for SOA records, and if
name is a dotted-decimal IPv4 address or colon-delimited IPv6 address,
host will query for PTR records. If a query type of IXFR is chosen the
starting serial number can be specified by appending an equal followed
by the starting serial number (e.g. -t IXFR=12345678).

The time to wait for a reply can be controlled through the -W and -w
options. The -W option makes host wait for wait seconds. If wait is
less than one, the wait interval is set to one second. When the -w
option is used, host will effectively wait forever for a reply. The
time to wait for a response will be set to the number of seconds given
by the hardware’s maximum value for an integer quantity.

The -s option tells host not to send the query to the next nameserver
if any server responds with a SERVFAIL response, which is the reverse
of normal stub resolver behavior.

The -m can be used to set the memory usage debugging flags record,
usage and trace.

The -V option causes host to print the version number and exit.

If host has been built with IDN (internationalized domain name)
support, it can accept and display non-ASCII domain names. host
appropriately converts character encoding of domain name before sending
a request to DNS server or displaying a reply from the server. If you’d
like to turn off the IDN support for some reason, defines the
IDN_DISABLE environment variable. The IDN support is disabled if the
variable is set when host runs.



dig, named(8).


Copyright © 2004, 2005, 2007-2009, 2014 Internet Systems Consortium,
Inc. (“ISC”)
Copyright © 2000-2002 Internet Software Consortium.

BIND9 January 20, 2009 HOST(1)

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