.\" Copyright (C) 2000-2002, 2004, 2005, 2007-2009, 2014-2020 Internet Systems Consortium, Inc. ("ISC")
.\" 
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.\"     Title: host
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 2009-01-20
.\"    Manual: BIND9
.\"    Source: ISC
.\"  Language: English
.\"
.TH "HOST" "1" "2009\-01\-20" "ISC" "BIND9"
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.SH "NAME"
host \- DNS lookup utility
.SH "SYNOPSIS"
.HP \w'\fBhost\fR\ 'u
\fBhost\fR [\fB\-aCdlnrsTUwv\fR] [\fB\-c\ \fR\fB\fIclass\fR\fR] [\fB\-N\ \fR\fB\fIndots\fR\fR] [\fB\-p\ \fR\fB\fIport\fR\fR] [\fB\-R\ \fR\fB\fInumber\fR\fR] [\fB\-t\ \fR\fB\fItype\fR\fR] [\fB\-W\ \fR\fB\fIwait\fR\fR] [\fB\-m\ \fR\fB\fIflag\fR\fR] [[\fB\-4\fR] | [\fB\-6\fR]] [\fB\-v\fR] [\fB\-V\fR] {name} [server]
.SH "DESCRIPTION"
.PP
\fBhost\fR
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,
\fBhost\fR
prints a short summary of its command line arguments and options\&.
.PP
\fIname\fR
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
\fBhost\fR
will by default perform a reverse lookup for that address\&.
\fIserver\fR
is an optional argument which is either the name or IP address of the name server that
\fBhost\fR
should query instead of the server or servers listed in
/etc/resolv\&.conf\&.
.SH "OPTIONS"
.PP
\-4
.RS 4
Use IPv4 only for query transport\&. See also the
\fB\-6\fR
option\&.
.RE
.PP
\-6
.RS 4
Use IPv6 only for query transport\&. See also the
\fB\-4\fR
option\&.
.RE
.PP
\-a
.RS 4
"All"\&. The
\fB\-a\fR
option is normally equivalent to
\fB\-v \-t \fR\fBANY\fR\&. It also affects the behaviour of the
\fB\-l\fR
list zone option\&.
.RE
.PP
\-c \fIclass\fR
.RS 4
Query class: This can be used to lookup HS (Hesiod) or CH (Chaosnet) class resource records\&. The default class is IN (Internet)\&.
.RE
.PP
\-C
.RS 4
Check consistency:
\fBhost\fR
will query the SOA records for zone
\fIname\fR
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\&.
.RE
.PP
\-d
.RS 4
Print debugging traces\&. Equivalent to the
\fB\-v\fR
verbose option\&.
.RE
.PP
\-i
.RS 4
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\&.
.RE
.PP
\-l
.RS 4
List zone: The
\fBhost\fR
command performs a zone transfer of zone
\fIname\fR
and prints out the NS, PTR and address records (A/AAAA)\&.
.sp
Together, the
\fB\-l \-a\fR
options print all records in the zone\&.
.RE
.PP
\-N \fIndots\fR
.RS 4
The number of dots that have to be in
\fIname\fR
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
\fBsearch\fR
or
\fBdomain\fR
directive in
/etc/resolv\&.conf\&.
.RE
.PP
\-p \fIport\fR
.RS 4
Specify the port on the server to query\&. The default is 53\&.
.RE
.PP
\-r
.RS 4
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
\fIname\fR\&. The
\fB\-r\fR
option enables
\fBhost\fR
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\&.
.RE
.PP
\-R \fInumber\fR
.RS 4
Number of retries for UDP queries: If
\fInumber\fR
is negative or zero, the number of retries will default to 1\&. The default value is 1, or the value of the
\fIattempts\fR
option in
/etc/resolv\&.conf, if set\&.
.RE
.PP
\-s
.RS 4
Do
\fInot\fR
send the query to the next nameserver if any server responds with a SERVFAIL response, which is the reverse of normal stub resolver behavior\&.
.RE
.PP
\-t \fItype\fR
.RS 4
Query type: The
\fItype\fR
argument can be any recognized query type: CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc\&.
.sp
When no query type is specified,
\fBhost\fR
automatically selects an appropriate query type\&. By default, it looks for A, AAAA, and MX records\&. If the
\fB\-C\fR
option is given, queries will be made for SOA records\&. If
\fIname\fR
is a dotted\-decimal IPv4 address or colon\-delimited IPv6 address,
\fBhost\fR
will query for PTR records\&.
.sp
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
\fB\-t \fR\fBIXFR=12345678\fR)\&.
.RE
.PP
\-T, \-U
.RS 4
TCP/UDP: By default,
\fBhost\fR
uses UDP when making queries\&. The
\fB\-T\fR
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\&. Type ANY queries default to TCP but can be forced to UDP initially using
\fB\-U\fR\&.
.RE
.PP
\-m \fIflag\fR
.RS 4
Memory usage debugging: the flag can be
\fIrecord\fR,
\fIusage\fR, or
\fItrace\fR\&. You can specify the
\fB\-m\fR
option more than once to set multiple flags\&.
.RE
.PP
\-v
.RS 4
Verbose output\&. Equivalent to the
\fB\-d\fR
debug option\&. Verbose output can also be enabled by setting the
\fIdebug\fR
option in
/etc/resolv\&.conf\&.
.RE
.PP
\-V
.RS 4
Print the version number and exit\&.
.RE
.PP
\-w
.RS 4
Wait forever: The query timeout is set to the maximum possible\&. See also the
\fB\-W\fR
option\&.
.RE
.PP
\-W \fIwait\fR
.RS 4
Timeout: Wait for up to
\fIwait\fR
seconds for a reply\&. If
\fIwait\fR
is less than one, the wait interval is set to one second\&.
.sp
By default,
\fBhost\fR
will wait for 5 seconds for UDP responses and 10 seconds for TCP connections\&. These defaults can be overridden by the
\fItimeout\fR
option in
/etc/resolv\&.conf\&.
.sp
See also the
\fB\-w\fR
option\&.
.RE
.SH "IDN SUPPORT"
.PP
If
\fBhost\fR
has been built with IDN (internationalized domain name) support, it can accept and display non\-ASCII domain names\&.
\fBhost\fR
appropriately converts character encoding of domain name before sending a request to DNS server or displaying a reply from the server\&. If you\*(Aqd like to turn off the IDN support for some reason, defines the
\fBIDN_DISABLE\fR
environment variable\&. The IDN support is disabled if the variable is set when
\fBhost\fR
runs\&.
.SH "FILES"
.PP
/etc/resolv\&.conf
.SH "SEE ALSO"
.PP
\fBdig\fR(1),
\fBnamed\fR(8)\&.
.SH "AUTHOR"
.PP
\fBInternet Systems Consortium, Inc\&.\fR
.SH "COPYRIGHT"
.br
Copyright \(co 2000-2002, 2004, 2005, 2007-2009, 2014-2020 Internet Systems Consortium, Inc. ("ISC")
.br