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7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi<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>] {name} [server]</p></div>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi<p><span><strong class="command">host</strong></span>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi is a simple utility for performing DNS lookups.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi It is normally used to convert names to IP addresses and vice versa.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi When no arguments or options are given,
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi prints a short summary of its command line arguments and options.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi<p><em class="parameter"><code>name</code></em> is the domain name that is to be
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi up. It can also be a dotted-decimal IPv4 address or a colon-delimited
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi IPv6 address, in which case <span><strong class="command">host</strong></span> will by
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi perform a reverse lookup for that address.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <em class="parameter"><code>server</code></em> is an optional argument which
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi the name or IP address of the name server that <span><strong class="command">host</strong></span>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi should query instead of the server or servers listed in
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi The <code class="option">-a</code> (all) option is equivalent to setting the
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi a query of type ANY.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi will attempt to display the SOA records for zone
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <em class="parameter"><code>name</code></em> from all the listed
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi authoritative name
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi servers for that zone. The list of name servers is defined by the NS
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi records that are found for the zone.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi The <code class="option">-c</code> option instructs to make a DNS query of class
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <em class="parameter"><code>class</code></em>. This can be used to lookup
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi Chaosnet class resource records. The default class is IN (Internet).
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi Verbose output is generated by <span><strong class="command">host</strong></span> when
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi options are equivalent. They have been provided for backwards
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi compatibility. In previous versions, the <code class="option">-d</code> option
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi switched on debugging traces and <code class="option">-v</code> enabled verbose
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi List mode is selected by the <code class="option">-l</code> option. This makes
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <span><strong class="command">host</strong></span> perform a zone transfer for zone
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <em class="parameter"><code>name</code></em>. Transfer the zone printing out
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun the NS, PTR
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun and address records (A/AAAA). If combined with <code class="option">-a</code>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi all records will be printed.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi option specifies that reverse lookups of IPv6 addresses should
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi use the IP6.INT domain as defined in RFC1886.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi The default is to use IP6.ARPA.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi The <code class="option">-N</code> option sets the number of dots that have to be
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi in <em class="parameter"><code>name</code></em> for it to be considered
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi absolute. The
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi default value is that defined using the ndots statement in
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi statement is
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi present. Names with fewer dots are interpreted as relative names and
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi will be searched for in the domains listed in the <span class="type">search</span>
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun The number of UDP retries for a lookup can be changed with the
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi how many times <span><strong class="command">host</strong></span> will repeat a query
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi not get answered. The default number of retries is 1. If
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <em class="parameter"><code>number</code></em> is negative or zero, the
22d3d2f9c62e27256dd183739faafe1f2e88bab6nilgun retries will default to 1.
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun Non-recursive queries can be made via the <code class="option">-r</code> option.
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun Setting this option clears the <span class="type">RD</span> — recursion
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun desired — bit in the query which <span><strong class="command">host</strong></span> makes.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi This should mean that the name server receiving the query will not
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi attempt to resolve <em class="parameter"><code>name</code></em>. The
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi the behaviour of a name server by making non-recursive queries and
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi expecting to receive answers to those queries that are usually
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi referrals to other name servers.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi By default <span><strong class="command">host</strong></span> uses UDP when making
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi queries. The
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="option">-T</code> option makes it use a TCP connection when querying
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi the name server. TCP will be automatically selected for queries that
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi require it, such as zone transfer (AXFR) requests.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi use IPv4 query transport. The <code class="option">-6</code> option forces
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <span><strong class="command">host</strong></span> to only use IPv6 query transport.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi The <code class="option">-t</code> option is used to select the query type.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <em class="parameter"><code>type</code></em> can be any recognised query
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi type: CNAME,
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <span><strong class="command">host</strong></span> automatically selects an appropriate
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi type. By default it looks for A records, but if the
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="option">-C</code> option was given, queries will be made for SOA
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi records, and if <em class="parameter"><code>name</code></em> is a
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi dotted-decimal IPv4
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi query for PTR records. If a query type of IXFR is chosen the starting
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi serial number can be specified by appending an equal followed by the
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi starting serial number (e.g. -t IXFR=12345678).
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi The time to wait for a reply can be controlled through the
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="option">-W</code> and <code class="option">-w</code> options. The
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi is less than one, the wait interval is set to one second. When the
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi effectively wait forever for a reply. The time to wait for a response
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi will be set to the number of seconds given by the hardware's maximum
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi value for an integer quantity.
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun if any server responds with a SERVFAIL response, which is the
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi reverse of normal stub resolver behaviour.
7927661fe7cf1c0c2eac0e9b1d146c2a2f6eb4eftakashi The <code class="option">-m</code> can be used to set the memory usage debugging
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun domain name) support, it can accept and display non-ASCII domain names.
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun <span><strong class="command">host</strong></span> appropriately converts character encoding of
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun domain name before sending a request to DNS server or displaying a
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun reply from the server.
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun If you'd like to turn off the IDN support for some reason, defines
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun the <code class="envar">IDN_DISABLE</code> environment variable.
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun The IDN support is disabled if the variable is set when
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun <span><strong class="command">host</strong></span> runs.
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
7fdd79a6e3620562e4f9062ed5cec77bedc06c67nilgun <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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