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1ac39787115a288f5e848344b1b1e8dccb1c58f1nd - Copyright (C) 2004-2012 Internet Systems Consortium, Inc. ("ISC")
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd - Copyright (C) 2000-2003 Internet Software Consortium.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd - Permission to use, copy, modify, and/or distribute this software for any
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd - purpose with or without fee is hereby granted, provided that the above
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd - copyright notice and this permission notice appear in all copies.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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1ac39787115a288f5e848344b1b1e8dccb1c58f1nd<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>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd is a simple utility for performing DNS lookups.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd It is normally used to convert names to IP addresses and vice versa.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd When no arguments or options are given,
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd prints a short summary of its command line arguments and options.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd<p><em class="parameter"><code>name</code></em> is the domain name that is to be
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd up. It can also be a dotted-decimal IPv4 address or a colon-delimited
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd IPv6 address, in which case <span><strong class="command">host</strong></span> will by
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd perform a reverse lookup for that address.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <em class="parameter"><code>server</code></em> is an optional argument which
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd the name or IP address of the name server that <span><strong class="command">host</strong></span>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd should query instead of the server or servers listed in
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The <code class="option">-a</code> (all) option is equivalent to setting the
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd a query of type ANY.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd will attempt to display the SOA records for zone
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <em class="parameter"><code>name</code></em> from all the listed
d03cac4d8ba79a23cfda410d35b614b0d805ba4cnilgun authoritative name
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd servers for that zone. The list of name servers is defined by the NS
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd records that are found for the zone.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The <code class="option">-c</code> option instructs to make a DNS query of class
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <em class="parameter"><code>class</code></em>. This can be used to lookup
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd Chaosnet class resource records. The default class is IN (Internet).
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd Verbose output is generated by <span><strong class="command">host</strong></span> when
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <code class="option">-d</code> or <code class="option">-v</code> option is used. The two
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd options are equivalent. They have been provided for backwards
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd compatibility. In previous versions, the <code class="option">-d</code> option
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd switched on debugging traces and <code class="option">-v</code> enabled verbose
d03cac4d8ba79a23cfda410d35b614b0d805ba4cnilgun List mode is selected by the <code class="option">-l</code> option. This makes
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <span><strong class="command">host</strong></span> perform a zone transfer for zone
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <em class="parameter"><code>name</code></em>. Transfer the zone printing out
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd the NS, PTR
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd and address records (A/AAAA). If combined with <code class="option">-a</code>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd all records will be printed.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd option specifies that reverse lookups of IPv6 addresses should
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd use the IP6.INT domain as defined in RFC1886.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The default is to use IP6.ARPA.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The <code class="option">-N</code> option sets the number of dots that have to be
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd in <em class="parameter"><code>name</code></em> for it to be considered
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd absolute. The
e1e8390280254f7f0580d701e583f670643d4f3fnilgun default value is that defined using the ndots statement in
d03cac4d8ba79a23cfda410d35b614b0d805ba4cnilgun <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd statement is
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd present. Names with fewer dots are interpreted as relative names and
e1e8390280254f7f0580d701e583f670643d4f3fnilgun will be searched for in the domains listed in the <span class="type">search</span>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The number of UDP retries for a lookup can be changed with the
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <code class="option">-R</code> option. <em class="parameter"><code>number</code></em>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd how many times <span><strong class="command">host</strong></span> will repeat a query
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd not get answered. The default number of retries is 1. If
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <em class="parameter"><code>number</code></em> is negative or zero, the
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd retries will default to 1.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd Non-recursive queries can be made via the <code class="option">-r</code> option.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd Setting this option clears the <span class="type">RD</span> — recursion
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd desired — bit in the query which <span><strong class="command">host</strong></span> makes.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd This should mean that the name server receiving the query will not
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd attempt to resolve <em class="parameter"><code>name</code></em>. The
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd the behavior of a name server by making non-recursive queries and
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd expecting to receive answers to those queries that are usually
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd referrals to other name servers.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd By default, <span><strong class="command">host</strong></span> uses UDP when making
e1e8390280254f7f0580d701e583f670643d4f3fnilgun queries. The
e1e8390280254f7f0580d701e583f670643d4f3fnilgun <code class="option">-T</code> option makes it use a TCP connection when querying
e1e8390280254f7f0580d701e583f670643d4f3fnilgun the name server. TCP will be automatically selected for queries that
e1e8390280254f7f0580d701e583f670643d4f3fnilgun require it, such as zone transfer (AXFR) requests.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd use IPv4 query transport. The <code class="option">-6</code> option forces
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <span><strong class="command">host</strong></span> to only use IPv6 query transport.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The <code class="option">-t</code> option is used to select the query type.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <em class="parameter"><code>type</code></em> can be any recognized query
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd type: CNAME,
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified,
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <span><strong class="command">host</strong></span> automatically selects an appropriate
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd type. By default, it looks for A, AAAA, and MX records, but if the
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <code class="option">-C</code> option was given, queries will be made for SOA
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd records, and if <em class="parameter"><code>name</code></em> is a
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd dotted-decimal IPv4
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd query for PTR records. If a query type of IXFR is chosen the starting
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd serial number can be specified by appending an equal followed by the
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd starting serial number (e.g. -t IXFR=12345678).
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The time to wait for a reply can be controlled through the
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <code class="option">-W</code> and <code class="option">-w</code> options. The
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
d03cac4d8ba79a23cfda410d35b614b0d805ba4cnilgun <em class="parameter"><code>wait</code></em> seconds. If <em class="parameter"><code>wait</code></em>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd is less than one, the wait interval is set to one second. When the
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd effectively wait forever for a reply. The time to wait for a response
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd will be set to the number of seconds given by the hardware's maximum
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd value for an integer quantity.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd if any server responds with a SERVFAIL response, which is the
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd reverse of normal stub resolver behavior.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The <code class="option">-m</code> can be used to set the memory usage debugging
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd domain name) support, it can accept and display non-ASCII domain names.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <span><strong class="command">host</strong></span> appropriately converts character encoding of
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd domain name before sending a request to DNS server or displaying a
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd reply from the server.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd If you'd like to turn off the IDN support for some reason, defines
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd the <code class="envar">IDN_DISABLE</code> environment variable.
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd The IDN support is disabled if the variable is set when
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd<p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
1ac39787115a288f5e848344b1b1e8dccb1c58f1nd <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
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