bind9/bin/dig/host.1

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.\" $Id: host.1,v 1.2 2000/07/27 09:42:26 tale Exp $
.\" 
.Dd Jun 30, 2000
.Dt HOST 1
.Os BIND9 9
.ds vT BIND9 Programmer's Manual
.Sh NAME
.Nm host
.Nd DNS lookup utility
.Sh SYNOPSIS
.Nm host
.Op Fl aCdlrTwv
.Op Fl c Ar class
.Op Fl N Ar ndots
.Op Fl R Ar number
.Op Fl t Ar type
.Op Fl W Ar wait
.Ar name
.Op Ar server
.Sh DESCRIPTION
.Nm 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,
.Nm host
prints a short summary of its command line arguments and options.
.Pp
.Ar name
is the domain name that is to be looked up.
It can also be a dotted-decimal string representing an IPv4 address, 
in which case
.Nm host
will by default perform a reverse lookup for that address.
.Ar server
is an optional argument which is either the name or IP address of the
name server that
.Nm host
should query instead of the server or servers listed in
.Pa /etc/resolv.conf .
.Pp
The
.Fl a
(all) option is equivalent to setting the
.Fl v
option and asking 
.Nm host
to make a query of type ANY.
.Pp
When the
.Fl C
option is used,
.Nm host
will attempt to display the SOA records for zone
.Ar 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.
.Pp
The
.Fl c
option instructs to make a DNS query of class
.Ar class .
This can be used to lookup Hesiod or Chaosnet class resource records.
The default class is IN: Internet.
.Pp
Verbose output is generated by
.Nm host
when the
.Fl d
or
.Fl v
option is used.
The two options are equivalent.
They have been provided for backwards compatibility.
In previous versions, the
.Fl d
option switched on debugging traces and
.Fl v
enabled verbose output.
.Pp
List mode is selected by the
.Fl l
option.
This makes 
.Nm host
perform a zone transfer for zone
.Ar name .
The argument is provided for compatibility with older implemementations.
This option is equivalent to making a query of type AXFR.
.Pp
The
.Fl N
option sets the number of dots that have to be in
.Ar name
before the root name servers are queried for that name.
The default number of dots is zero.
Unlike previous versions of
.Nm host ,
the BIND9 implementation does not append domain names from the
.Dv domain
or
.Dv search
directives in 
.Pa /etc/resolv.conf .
Therefore
.Ar name
should be a fully-qualified domain name.
.Pp
The number of UDP retries for a lookup can be changed with the
.Fl R
option.
.Ar number
indicates how many times
.Nm host
will repeat a query that does not get answered.
The default number of retries is 1.
If
.Ar number
is negative or zero, the number of retries will default to 1.
.Pp
Non-recursive queries can be made via the
.Fl r
option.
Setting this option clears the
.Dv RD
- recursion desired - bit in the query which
.Nm host
makes.
This should mean that the name server receiving the query will not attemp
to resolve
.Ar name .
The
.Fl r
option enables
.Nm 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.
.Pp
By default
.Nm host
uses UDP when making queries.
The
.Fl T
option makes it use a TCP connection when querying the name server.
TCP queries will be automatically made when the query type requires
that a TCP connection: zone transfer (AXFR) requests for example.
.Pp
The
.Fl t
option is used to select the query type.
.Ar type
can be any recognised query type: CNAME, NS, SOA, SIG, KEY, AXFR, etc.
When no query type is specified, 
.Nm host
automatically selects an appropriate query type.
By default it looks for A records unless the
.Fl C
option is supplied or
.Ar name
is a dotted-decimal IPv4 address.
These will make
.Nm host
look for SOA and PTR records respectively.
.Pp
The time to wait for a reply can be controlled through the
.Fl W
and
.Fl w
options.
The
.Fl W
option makes
.Nm host
wait for 
.Ar wait
seconds.
If
.Ar wait
is less than one,
the wait interval is set to one second.
When the
.Fl w
option is used,
.Nm 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.
.Sh FILES
.Pa /etc/resolv.conf
.Sh SEE ALSO
.Xr dig 1 ,
.Xr resolver 5
.Xr named 8 .
.Sh BUGS
.Nm host
does not yet know how to handle command line arguments that are IPv6
addresses, even though the record types for those addresses are
fully supported by the BIND9 DNS library.
.Pp
Apart from this self-contradicting sentence, the
.Fl D
option is undocumented.