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.Dd $Mdocdate: March 31 2022 $
.Dt HOST 1
.Os
.Sh NAME
.Nm host
.Nd DNS lookup utility
.Sh SYNOPSIS
.Nm
.Op Fl 46aCdilrsTVvw
.Op Fl c Ar class
.Op Fl m Ar flag
.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
The
.Nm
command is a simple utility for performing DNS lookups.
It is normally used to convert names to IP addresses and vice versa.
.Pp
.Ar 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
.Nm
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
should query instead of the server or servers listed in
.Pa /etc/resolv.conf .
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl 4
Use IPv4 only for query transport.
.It Fl 6
Use IPv6 only for query transport.
.It Fl a
"All".
The
.Fl a
option is normally equivalent to
.Fl v
.Fl t Cm ANY .
It also affects the behaviour of the
.Fl l
list zone option.
.It Fl C
Check consistency:
.Nm
will query 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.
.It Fl c Ar class
Query class: This can be used to lookup
.Cm HS
(Hesiod)
or
.Cm CH
(Chaosnet) class resource records.
The default class is
.Cm IN
(Internet).
.It Fl d
Print debugging traces.
Equivalent to the
.Fl v
verbose option.
.It Fl i
Obsolete.
Use the IP6.INT domain for reverse lookups of IPv6 addresses as defined in
RFC 1886 and deprecated in RFC 4159.
The default is to use IP6.ARPA as specified in RFC 3596.
.It Fl l
List zone:
The
.Nm
command performs a zone transfer of
zone
.Ar name
and prints out the NS, PTR and address records (A/AAAA).
.Pp
Together, the
.Fl l
.Fl a
options print all records in the zone.
.It Fl m Ar flag
Memory usage debugging: the flag can be
.Cm record ,
.Cm usage ,
or
.Cm trace .
You can specify the
.Fl m
option more than once to set multiple flags.
.It Fl N Ar ndots
The number of dots that have to be in
.Ar name
for it to be considered absolute.
The default value is that defined using the ndots statement in
.Pa /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
.Vt search
or
.Vt domain
directive in
.Pa /etc/resolv.conf .
.It Fl R Ar number
Number of retries for UDP queries:
If
.Ar number
is negative or zero, the number of retries will default to 1.
The default value is 1.
.It Fl 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
.Ar name .
The
.Fl r
option enables
.Nm
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.
.It Fl s
Do
.Em not
send the query to the next name server if any server responds with a SERVFAIL
response, which is the reverse of normal stub resolver behavior.
.It Fl T
TCP:
By default,
.Nm
uses UDP when making queries.
The
.Fl 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.
.It Fl t Ar type
Query type:
The
.Ar type
argument can be any recognized query type:
.Cm CNAME ,
.Cm NS ,
.Cm SOA ,
.Cm TXT ,
.Cm DNSKEY ,
.Cm AXFR ,
etc.
.Pp
When no query type is specified,
.Nm
automatically selects an appropriate query type.
By default, it looks for A, AAAA, and MX records.
If the
.Fl C
option is given, queries will be made for SOA records.
If
.Ar name
is a dotted-decimal IPv4 address or colon-delimited IPv6 address,
.Nm
will query for PTR records.
.Pp
If a query type of
.Cm IXFR
is chosen, the starting serial number can be specified by appending an equal
followed by the starting serial number (like
.Fl t Cm IXFR= Ns Ar 12345678 ) .
.It Fl V
Print the version number and exit.
.It Fl v
Verbose output.
Equivalent to the
.Fl d
debug option.
.It Fl W Ar wait
Timeout: Wait for up to
.Ar wait
seconds for a reply.
If
.Ar wait
is less than one, the wait interval is set to one second.
.Pp
By default,
.Nm
will wait for 5 seconds for UDP responses and 10 seconds for TCP connections.
.It Fl w
Wait forever: The query timeout is set to the maximum possible.
.El
.Sh FILES
.Pa /etc/resolv.conf
.Sh SEE ALSO
.Xr dig 1
.Sh AUTHORS
.An -nosplit
.An Internet Systems Consortium, Inc .