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919N/A<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry">
919N/A<a name="man.host"></a><div class="titlepage"></div>
153N/A<div class="refnamediv">
153N/A<h2>Name</h2>
153N/A<p>host &#8212; DNS lookup utility</p>
153N/A</div>
493N/A<div class="refsynopsisdiv">
153N/A<h2>Synopsis</h2>
153N/A<div class="cmdsynopsis"><p><code class="command">host</code> [<code class="option">-aCdlnrsTwv</code>] [<code class="option">-c <em class="replaceable"><code>class</code></em></code>] [<code class="option">-N <em class="replaceable"><code>ndots</code></em></code>] [<code class="option">-R <em class="replaceable"><code>number</code></em></code>] [<code class="option">-t <em class="replaceable"><code>type</code></em></code>] [<code class="option">-W <em class="replaceable"><code>wait</code></em></code>] [<code class="option">-m <em class="replaceable"><code>flag</code></em></code>] [<code class="option">-4</code>] [<code class="option">-6</code>] [<code class="option">-v</code>] [<code class="option">-V</code>] {name} [server]</p></div>
962N/A</div>
153N/A<div class="refsection">
911N/A<a name="id-1.7"></a><h2>DESCRIPTION</h2>
962N/A<p><span class="command"><strong>host</strong></span>
962N/A is a simple utility for performing DNS lookups.
911N/A It is normally used to convert names to IP addresses and vice versa.
153N/A When no arguments or options are given,
153N/A <span class="command"><strong>host</strong></span>
153N/A prints a short summary of its command line arguments and options.
153N/A </p>
153N/A<p><em class="parameter"><code>name</code></em> is the domain name that is to be
153N/A looked
970N/A up. It can also be a dotted-decimal IPv4 address or a colon-delimited
970N/A IPv6 address, in which case <span class="command"><strong>host</strong></span> will by
970N/A default
970N/A perform a reverse lookup for that address.
970N/A <em class="parameter"><code>server</code></em> is an optional argument which
970N/A is either
153N/A the name or IP address of the name server that <span class="command"><strong>host</strong></span>
153N/A should query instead of the server or servers listed in
493N/A <code class="filename">/etc/resolv.conf</code>.
969N/A </p>
153N/A</div>
493N/A<div class="refsection">
153N/A<a name="id-1.8"></a><h2>OPTIONS</h2>
153N/A<div class="variablelist"><dl class="variablelist">
153N/A<dt><span class="term">-4</span></dt>
153N/A<dd><p>
153N/A Use IPv4 only for query transport.
493N/A See also the <code class="option">-6</code> option.
153N/A </p></dd>
970N/A<dt><span class="term">-6</span></dt>
970N/A<dd><p>
970N/A Use IPv6 only for query transport.
153N/A See also the <code class="option">-4</code> option.
</p></dd>
<dt><span class="term">-a</span></dt>
<dd><p>
"All". The <code class="option">-a</code> option is normally equivalent
to <code class="option">-v</code> <code class="option">-t</code> <code class="literal">ANY</code>.
It also affects the behaviour of the <code class="option">-l</code>
list zone option.
</p></dd>
<dt><span class="term">-c <em class="replaceable"><code>class</code></em></span></dt>
<dd><p>
Query class: This can be used to lookup Hesiod or Chaosnet
class resource records. The default class is IN
(Internet).
</p></dd>
<dt><span class="term">-C</span></dt>
<dd><p>
Check consistency: <span class="command"><strong>host</strong></span> will query the
SOA records for zone <em class="parameter"><code>name</code></em> 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.
</p></dd>
<dt><span class="term">-d</span></dt>
<dd><p>
Print debugging traces.
Equivalent to the <code class="option">-v</code> verbose option.
</p></dd>
<dt><span class="term">-i</span></dt>
<dd><p>
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.
</p></dd>
<dt><span class="term">-l</span></dt>
<dd>
<p>
List zone:
The <span class="command"><strong>host</strong></span> performs a zone transfer of
zone <em class="parameter"><code>name</code></em> and prints out the NS,
PTR and address records (A/AAAA).
</p>
<p>
Together, the <code class="option">-l</code> <code class="option">-a</code>
options print all records in the zone.
</p>
</dd>
<dt><span class="term">-N <em class="replaceable"><code>ndots</code></em></span></dt>
<dd><p>
The number of dots that have to be
in <em class="parameter"><code>name</code></em> for it to be considered
absolute. The default value is that defined using the
ndots statement in <code class="filename">/etc/resolv.conf</code>,
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 <span class="type">search</span> or <span class="type">domain</span> directive
in <code class="filename">/etc/resolv.conf</code>.
</p></dd>
<dt><span class="term">-r</span></dt>
<dd><p>
Non-recursive query:
Setting this option clears the <span class="type">RD</span> &#8212;
recursion desired &#8212; bit in the query. This should
mean that the name server receiving the query will not
attempt to resolve <em class="parameter"><code>name</code></em>.
The <code class="option">-r</code> option
enables <span class="command"><strong>host</strong></span> 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.
</p></dd>
<dt><span class="term">-R <em class="replaceable"><code>number</code></em></span></dt>
<dd><p>
Number of retries for UDP queries:
If <em class="parameter"><code>number</code></em> is negative or zero, the
number of retries will default to 1. The default value is
1, or the value of the <em class="parameter"><code>attempts</code></em>
option in <code class="filename">/etc/resolv.conf</code>, if set.
</p></dd>
<dt><span class="term">-s</span></dt>
<dd><p>
Do <span class="emphasis"><em>not</em></span> send the query to the next
nameserver if any server responds with a SERVFAIL
response, which is the reverse of normal stub resolver
behavior.
</p></dd>
<dt><span class="term">-t <em class="replaceable"><code>type</code></em></span></dt>
<dd>
<p>
Query type:
the <em class="parameter"><code>type</code></em> argument can be any
recognized query type: CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc.
</p>
<p>
When no query type is specified, <span class="command"><strong>host</strong></span>
automatically selects an appropriate query type. By default, it
looks for A, AAAA, and MX records.
If the <code class="option">-C</code> option is given, queries will
be made for SOA records.
If <em class="parameter"><code>name</code></em> is a dotted-decimal IPv4
address or colon-delimited IPv6
address, <span class="command"><strong>host</strong></span> will query for PTR
records.
</p>
<p>
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
(e.g. <code class="option">-t</code> <code class="literal">IXFR=12345678</code>).
</p>
</dd>
<dt><span class="term">-T</span></dt>
<dd><p>
TCP:
By default, <span class="command"><strong>host</strong></span> uses UDP when making
queries. The <code class="option">-T</code> 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.
</p></dd>
<dt><span class="term">-m <em class="replaceable"><code>flag</code></em></span></dt>
<dd><p>
Memory usage debugging: the flag can
be <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em>,
or <em class="parameter"><code>trace</code></em>. You can specify
the <code class="option">-m</code> option more than once to set
multiple flags.
</p></dd>
<dt><span class="term">-v</span></dt>
<dd><p>
Verbose output.
Equivalent to the <code class="option">-d</code> debug option.
Verbose output can also be enabled by setting
the <em class="parameter"><code>debug</code></em> option
in<code class="filename">/etc/resolv.conf</code>.
</p></dd>
<dt><span class="term">-V</span></dt>
<dd><p>
Print the version number and exit.
</p></dd>
<dt><span class="term">-w</span></dt>
<dd><p>
Wait forever: the query timeout is set to the maximum possible.
See also the <code class="option">-W</code> option.
</p></dd>
<dt><span class="term">-W <em class="replaceable"><code>wait</code></em></span></dt>
<dd>
<p>
Timeout: wait for up to <em class="parameter"><code>wait</code></em>
seconds for a reply. If <em class="parameter"><code>wait</code></em> is
less than one, the wait interval is set to one second.
</p>
<p>
By default, <span class="command"><strong>host</strong></span> will wait for 5
seconds for UDP responses and 10 seconds for TCP
connections. These defaults can be overridden by
the <em class="parameter"><code>timeout</code></em> option
in <code class="filename">/etc/resolv.conf</code>.
</p>
<p>
See also the <code class="option">-w</code> option.
</p>
</dd>
</dl></div>
</div>
<div class="refsection">
<a name="id-1.9"></a><h2>IDN SUPPORT</h2>
<p>
If <span class="command"><strong>host</strong></span> has been built with IDN (internationalized
domain name) support, it can accept and display non-ASCII domain names.
<span class="command"><strong>host</strong></span> 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 <code class="envar">IDN_DISABLE</code> environment variable.
The IDN support is disabled if the variable is set when
<span class="command"><strong>host</strong></span> runs.
</p>
</div>
<div class="refsection">
<a name="id-1.10"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
</p>
</div>
<div class="refsection">
<a name="id-1.11"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
<span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
</p>
</div>
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