NAME [Toc] [Back]
host - DNS lookup utility
SYNOPSIS [Toc] [Back]
host [-aCdlnrTwv] [-c class] [-N ndots] [-R number] [-t type]
[-W wait] name server
DESCRIPTION [Toc] [Back]
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.
Arguments [Toc] [Back]
name This is the domain name that is to be looked up. It
can also be a dotted-decimal IPv4 address or a colondelimited
IPv6 address, in which case host will by
default perform a reverse lookup for that address.
server This 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
Options [Toc] [Back]
a This option is equivalent to setting the v option and
asking host to make a query of type ANY.
C When this 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.
c class This option instructs host 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, for
d v Verbose output is generated by host when one of these
options are 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.
l List mode is selected by this option. This makes host
perform a zone transfer for zone name. The argument is
provided for compatibility with older
implemementations. This option is equivalent to making
a query of type AXFR.
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n This option specifies that reverse lookups of IPv6
addresses should use the IP6.INT domain and "nibble"
labels as defined in RFC1886. The default is to use
IP6.ARPA and binary labels as defined in RFC2874.
N ndots This option sets the number of dots that have to be in
name for it to be considered absolute. The default
value is 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
R number The number of UDP retries for a lookup can be changed
with this 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.
r Non-recursive queries can be made via this 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.
This option enables host to mimic the behaviour 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.
T This option makes host to 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. By default host uses UDP
when making queries.
t type This option is used to select the query type. type can
be any recognised 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 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 colondelimited
IPv6 address, host will query for PTR
W wait The time to wait for a reply can be controlled through
the W option. This option makes host wait for wait
seconds. If wait is less than 1, the wait interval is
set to one second.
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w When this 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.
FILES [Toc] [Back]
SEE ALSO [Toc] [Back]
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