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3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉<hr>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff</div>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff<div class="refentry" lang="en">
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff<a name="man.host"></a><div class="titlepage"></div>
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉<div class="refnamediv">
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉<h2>Name</h2>
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉<p>host &#8212; DNS lookup utility</p>
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉</div>
97a19a9ad60796faaa9eb851c0b84ff2f8a4211bTatuya JINMEI 神明達哉<div class="refsynopsisdiv">
97a19a9ad60796faaa9eb851c0b84ff2f8a4211bTatuya JINMEI 神明達哉<h2>Synopsis</h2>
97a19a9ad60796faaa9eb851c0b84ff2f8a4211bTatuya JINMEI 神明達哉<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>
97a19a9ad60796faaa9eb851c0b84ff2f8a4211bTatuya JINMEI 神明達哉</div>
97a19a9ad60796faaa9eb851c0b84ff2f8a4211bTatuya JINMEI 神明達哉<div class="refsect1" lang="en">
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉<a name="id2615962"></a><h2>DESCRIPTION</h2>
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉<p><span><strong class="command">host</strong></span>
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 is a simple utility for performing DNS lookups.
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 It is normally used to convert names to IP addresses and vice versa.
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 When no arguments or options are given,
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 <span><strong class="command">host</strong></span>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff prints a short summary of its command line arguments and options.
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff </p>
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson<p><em class="parameter"><code>name</code></em> is the domain name that is to be
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson looked
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff up. It can also be a dotted-decimal IPv4 address or a colon-delimited
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 IPv6 address, in which case <span><strong class="command">host</strong></span> will by
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 default
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 perform a reverse lookup for that address.
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 <em class="parameter"><code>server</code></em> is an optional argument which
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff is either
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff the name or IP address of the name server that <span><strong class="command">host</strong></span>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff should query instead of the server or servers listed in
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff <code class="filename">/etc/resolv.conf</code>.
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff </p>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff<p>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff The <code class="option">-a</code> (all) option is equivalent to setting the
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff a query of type ANY.
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff </p>
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson<p>
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff will attempt to display the SOA records for zone
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff <em class="parameter"><code>name</code></em> from all the listed
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff authoritative name
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff servers for that zone. The list of name servers is defined by the NS
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff records that are found for the zone.
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff </p>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff<p>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff The <code class="option">-c</code> option instructs to make a DNS query of class
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson <em class="parameter"><code>class</code></em>. This can be used to lookup
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff Hesiod or
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff Chaosnet class resource records. The default class is IN (Internet).
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff </p>
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson<p>
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson Verbose output is generated by <span><strong class="command">host</strong></span> when
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff the
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff options are equivalent. They have been provided for backwards
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff compatibility. In previous versions, the <code class="option">-d</code> option
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff switched on debugging traces and <code class="option">-v</code> enabled verbose
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff output. Verbose output can also be enabled by setting the
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson <em class="parameter"><code>debug</code></em> option in
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff <code class="filename">/etc/resolv.conf</code>.
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff </p>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff<p>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff List mode is selected by the <code class="option">-l</code> option. This makes
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff <span><strong class="command">host</strong></span> perform a zone transfer for zone
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff <em class="parameter"><code>name</code></em>. Transfer the zone printing out
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff the NS, PTR
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 and address records (A/AAAA). If combined with <code class="option">-a</code>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff all records will be printed.
4ac00f66832747f88c552904f7716571d3349d81Tatuya JINMEI 神明達哉 </p>
26a455b8206621c3e470dbea1f172d78f5a0e56bMichael Graff<p>
3da9aeb80704bdd45aaf5971d1a06cbd13580ca9Tatuya JINMEI 神明達哉 The <code class="option">-i</code>
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson option specifies that reverse lookups of IPv6 addresses should
9023c42352944fd58ae14d961b60c46cd246ed25Andreas Gustafsson use the IP6.INT domain as defined in RFC1886.
4ac00f66832747f88c552904f7716571d3349d81Tatuya JINMEI 神明達哉 The default is to use IP6.ARPA.
</p>
<p>
The <code class="option">-N</code> option sets 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>
<p>
The number of UDP retries for a lookup can be changed with the
<code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
indicates
how many times <span><strong class="command">host</strong></span> will repeat a query
that does
not get answered. 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>
<p>
Non-recursive queries can be made via the <code class="option">-r</code> option.
Setting this option clears the <span class="type">RD</span> &#8212; recursion
desired &#8212; bit in the query which <span><strong class="command">host</strong></span> makes.
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><strong class="command">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 are usually
referrals to other name servers.
</p>
<p>
By default, <span><strong class="command">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>
<p>
The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
use IPv4 query transport. The <code class="option">-6</code> option forces
<span><strong class="command">host</strong></span> to only use IPv6 query transport.
</p>
<p>
The <code class="option">-t</code> option is used to select the query type.
<em class="parameter"><code>type</code></em> can be any recognized query
type: CNAME,
NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
<span><strong class="command">host</strong></span> automatically selects an appropriate
query
type. By default, it looks for A, AAAA, and MX records, but if the
<code class="option">-C</code> option was given, queries will be made for SOA
records, and if <em class="parameter"><code>name</code></em> is a
dotted-decimal IPv4
address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
query for PTR records. 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. -t IXFR=12345678).
</p>
<p>
The time to wait for a reply can be controlled through the
<code class="option">-W</code> and <code class="option">-w</code> options. The
<code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
wait for
<em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
is less than one, the wait interval is set to one second. When the
<code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
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. By default, <span><strong class="command">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>
The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
<span class="emphasis"><em>not</em></span> to 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>
<p>
The <code class="option">-m</code> can be used to set the memory usage debugging
flags
<em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
<em class="parameter"><code>trace</code></em>.
</p>
<p>
The <code class="option">-V</code> option causes <span><strong class="command">host</strong></span>
to print the version number and exit.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2616867"></a><h2>IDN SUPPORT</h2>
<p>
If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
domain name) support, it can accept and display non-ASCII domain names.
<span><strong class="command">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><strong class="command">host</strong></span> runs.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2616896"></a><h2>FILES</h2>
<p><code class="filename">/etc/resolv.conf</code>
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2616909"></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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