host
HOST(1) BIND9 HOST(1)
NAME
host - DNS lookup utility
SYNOPSIS
host [-aCdlnrsTwv] [-c class] [-N ndots] [-R number] [-t type] [-W wait]
[-m flag] [-4] [-6] [-v] [-V] {name} [server]
DESCRIPTION
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.
OPTIONS
-4
Use IPv4 only for query transport. See also the -6 option.
-6
Use IPv6 only for query transport. See also the -4 option.
-a
"All". The -a option is normally equivalent to -v -t ANY. It also
affects the behaviour of the -l list zone option.
-c class
Query class: This can be used to lookup HS (Hesiod) or CH (Chaosnet)
class resource records. The default class is IN (Internet).
-C
Check consistency: host will query 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.
-d
Print debugging traces. Equivalent to the -v verbose option.
-i
Obsolete. Use the IP6.INT domain for reverse lookups of IPv6
addresses as defined in RFC1886 and deprecated in RFC4159. The
default is to use IP6.ARPA as specified in RFC3596.
-l
List zone: The host command performs a zone transfer of zone name and
prints out the NS, PTR and address records (A/AAAA).
Together, the -l -a options print all records in the zone.
-N ndots
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.
-r
Non-recursive query: Setting this option clears the RD (recursion
desired) bit in the query. 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 can be referrals to other name servers.
-R number
Number of retries for UDP queries: If number is negative or zero, the
number of retries will default to 1. The default value is 1.
-s
Do not send the query to the next nameserver if any server responds
with a SERVFAIL response, which is the reverse of normal stub
resolver behavior.
-t type
Query type: The type argument can be any recognized query type:
CNAME, NS, SOA, TXT, DNSKEY, 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. If the -C option is given, queries will be made for SOA
records. 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 (like -t IXFR=12345678).
-T
TCP: 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.
-m flag
Memory usage debugging: the flag can be record, usage, or trace. You
can specify the -m option more than once to set multiple flags.
-v
Verbose output. Equivalent to the -d debug option.
-V
Print the version number and exit.
-w
Wait forever: The query timeout is set to the maximum possible. See
also the -W option.
-W wait
Timeout: Wait for up to wait seconds for a reply. If wait is less
than one, the wait interval is set to one second.
By default, host will wait for 5 seconds for UDP responses and 10
seconds for TCP connections.
See also the -w option.
macOS NOTICE
The host command does not use the host name and address resolution or the
DNS query routing mechanisms used by other processes running on macOS.
The results of name or address queries printed by host may differ from
those found by other processes that use the macOS native name and address
resolution mechanisms. The results of DNS queries may also differ from
queries that use the macOS DNS routing library.
IDN SUPPORT
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.
FILES
/etc/resolv.conf
SEE ALSO
dig(1), named(8).
AUTHOR
Internet Systems Consortium, Inc.
COPYRIGHT
Copyright © 2004, 2005, 2007-2009, 2014-2016 Internet Systems Consortium,
Inc. ("ISC")
Copyright © 2000-2002 Internet Software Consortium.
ISC 2018-05-25 HOST(1)