external/bsd/bind/dist/bin/dig/host.html

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  18 <html>
  19 <head>
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  21 <title>host</title>
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  24 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
  25 <a name="man.host"></a><div class="titlepage"></div>
  26 <div class="refnamediv">
  27 <h2>Name</h2>
  28 <p>host &#8212; DNS lookup utility</p>
  29 </div>
  30 <div class="refsynopsisdiv">
  31 <h2>Synopsis</h2>
  32 <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>
  33 </div>
  34 <div class="refsect1" lang="en">
  35 <a name="id2543454"></a><h2>DESCRIPTION</h2>
  36 <p><span><strong class="command">host</strong></span>
  37       is a simple utility for performing DNS lookups.
  38       It is normally used to convert names to IP addresses and vice versa.
  39       When no arguments or options are given,
  40       <span><strong class="command">host</strong></span>
  41       prints a short summary of its command line arguments and options.
  42     </p>
  43 <p><em class="parameter"><code>name</code></em> is the domain name that is to be
  44       looked
  45       up.  It can also be a dotted-decimal IPv4 address or a colon-delimited
  46       IPv6 address, in which case <span><strong class="command">host</strong></span> will by
  47       default
  48       perform a reverse lookup for that address.
  49       <em class="parameter"><code>server</code></em> is an optional argument which
  50       is either
  51       the name or IP address of the name server that <span><strong class="command">host</strong></span>
  52       should query instead of the server or servers listed in
  53       <code class="filename">/etc/resolv.conf</code>.
  54     </p>
  55 <p>
  56       The <code class="option">-a</code> (all) option is equivalent to setting the
  57       <code class="option">-v</code> option and asking <span><strong class="command">host</strong></span> to make
  58       a query of type ANY.
  59     </p>
  60 <p>
  61       When the <code class="option">-C</code> option is used, <span><strong class="command">host</strong></span>
  62       will attempt to display the SOA records for zone
  63       <em class="parameter"><code>name</code></em> from all the listed
  64       authoritative name
  65       servers for that zone.  The list of name servers is defined by the NS
  66       records that are found for the zone.
  67     </p>
  68 <p>
  69       The <code class="option">-c</code> option instructs to make a DNS query of class
  70       <em class="parameter"><code>class</code></em>.  This can be used to lookup
  71       Hesiod or
  72       Chaosnet class resource records.  The default class is IN (Internet).
  73     </p>
  74 <p>
  75       Verbose output is generated by <span><strong class="command">host</strong></span> when
  76       the
  77       <code class="option">-d</code> or <code class="option">-v</code> option is used.  The two
  78       options are equivalent.  They have been provided for backwards
  79       compatibility.  In previous versions, the <code class="option">-d</code> option
  80       switched on debugging traces and <code class="option">-v</code> enabled verbose
  81       output.
  82     </p>
  83 <p>
  84       List mode is selected by the <code class="option">-l</code> option.  This makes
  85       <span><strong class="command">host</strong></span> perform a zone transfer for zone
  86       <em class="parameter"><code>name</code></em>.  Transfer the zone printing out
  87       the NS, PTR
  88       and address records (A/AAAA).  If combined with <code class="option">-a</code>
  89       all records will be printed.
  90     </p>
  91 <p>
  92       The <code class="option">-i</code>
  93       option specifies that reverse lookups of IPv6 addresses should
  94       use the IP6.INT domain as defined in RFC1886.
  95       The default is to use IP6.ARPA.
  96     </p>
  97 <p>
  98       The <code class="option">-N</code> option sets the number of dots that have to be
  99       in <em class="parameter"><code>name</code></em> for it to be considered
 100       absolute.  The
 101       default value is that defined using the ndots statement in
 102       <code class="filename">/etc/resolv.conf</code>, or 1 if no ndots
 103       statement is
 104       present.  Names with fewer dots are interpreted as relative names and
 105       will be searched for in the domains listed in the <span class="type">search</span>
 106       or <span class="type">domain</span> directive in
 107       <code class="filename">/etc/resolv.conf</code>.
 108     </p>
 109 <p>
 110       The number of UDP retries for a lookup can be changed with the
 111       <code class="option">-R</code> option.  <em class="parameter"><code>number</code></em>
 112       indicates
 113       how many times <span><strong class="command">host</strong></span> will repeat a query
 114       that does
 115       not get answered.  The default number of retries is 1.  If
 116       <em class="parameter"><code>number</code></em> is negative or zero, the
 117       number of
 118       retries will default to 1.
 119     </p>
 120 <p>
 121       Non-recursive queries can be made via the <code class="option">-r</code> option.
 122       Setting this option clears the <span class="type">RD</span> &#8212; recursion
 123       desired &#8212; bit in the query which <span><strong class="command">host</strong></span> makes.
 124       This should mean that the name server receiving the query will not
 125       attempt to resolve <em class="parameter"><code>name</code></em>.  The
 126       <code class="option">-r</code> option enables <span><strong class="command">host</strong></span>
 127       to mimic
 128       the behavior of a name server by making non-recursive queries and
 129       expecting to receive answers to those queries that are usually
 130       referrals to other name servers.
 131     </p>
 132 <p>
 133       By default, <span><strong class="command">host</strong></span> uses UDP when making
 134       queries.  The
 135       <code class="option">-T</code> option makes it use a TCP connection when querying
 136       the name server.  TCP will be automatically selected for queries that
 137       require it, such as zone transfer (AXFR) requests.
 138     </p>
 139 <p>
 140       The <code class="option">-4</code> option forces <span><strong class="command">host</strong></span> to only
 141       use IPv4 query transport.  The <code class="option">-6</code> option forces
 142       <span><strong class="command">host</strong></span> to only use IPv6 query transport.
 143     </p>
 144 <p>
 145       The <code class="option">-t</code> option is used to select the query type.
 146       <em class="parameter"><code>type</code></em> can be any recognized query
 147       type: CNAME,
 148       NS, SOA, SIG, KEY, AXFR, etc.  When no query type is specified,
 149       <span><strong class="command">host</strong></span> automatically selects an appropriate
 150       query
 151       type.  By default, it looks for A, AAAA, and MX records, but if the
 152       <code class="option">-C</code> option was given, queries will be made for SOA
 153       records, and if <em class="parameter"><code>name</code></em> is a
 154       dotted-decimal IPv4
 155       address or colon-delimited IPv6 address, <span><strong class="command">host</strong></span> will
 156       query for PTR records.  If a query type of IXFR is chosen the starting
 157       serial number can be specified by appending an equal followed by the
 158       starting serial number (e.g. -t IXFR=12345678).
 159     </p>
 160 <p>
 161       The time to wait for a reply can be controlled through the
 162       <code class="option">-W</code> and <code class="option">-w</code> options.  The
 163       <code class="option">-W</code> option makes <span><strong class="command">host</strong></span>
 164       wait for
 165       <em class="parameter"><code>wait</code></em> seconds.  If <em class="parameter"><code>wait</code></em>
 166       is less than one, the wait interval is set to one second.  When the
 167       <code class="option">-w</code> option is used, <span><strong class="command">host</strong></span>
 168       will
 169       effectively wait forever for a reply.  The time to wait for a response
 170       will be set to the number of seconds given by the hardware's maximum
 171       value for an integer quantity.
 172     </p>
 173 <p>
 174       The <code class="option">-s</code> option tells <span><strong class="command">host</strong></span>
 175       <span class="emphasis"><em>not</em></span> to send the query to the next nameserver
 176       if any server responds with a SERVFAIL response, which is the
 177       reverse of normal stub resolver behavior.
 178     </p>
 179 <p>
 180       The <code class="option">-m</code> can be used to set the memory usage debugging
 181       flags
 182       <em class="parameter"><code>record</code></em>, <em class="parameter"><code>usage</code></em> and
 183       <em class="parameter"><code>trace</code></em>.
 184     </p>
 185 <p>
 186       The <code class="option">-V</code> option causes <span><strong class="command">host</strong></span>
 187       to print the version number and exit.
 188     </p>
 189 </div>
 190 <div class="refsect1" lang="en">
 191 <a name="id2543831"></a><h2>IDN SUPPORT</h2>
 192 <p>
 193       If <span><strong class="command">host</strong></span> has been built with IDN (internationalized
 194       domain name) support, it can accept and display non-ASCII domain names.
 195       <span><strong class="command">host</strong></span> appropriately converts character encoding of
 196       domain name before sending a request to DNS server or displaying a
 197       reply from the server.
 198       If you'd like to turn off the IDN support for some reason, defines
 199       the <code class="envar">IDN_DISABLE</code> environment variable.
 200       The IDN support is disabled if the variable is set when
 201       <span><strong class="command">host</strong></span> runs.
 202     </p>
 203 </div>
 204 <div class="refsect1" lang="en">
 205 <a name="id2543853"></a><h2>FILES</h2>
 206 <p><code class="filename">/etc/resolv.conf</code>
 207     </p>
 208 </div>
 209 <div class="refsect1" lang="en">
 210 <a name="id2543865"></a><h2>SEE ALSO</h2>
 211 <p><span class="citerefentry"><span class="refentrytitle">dig</span>(1)</span>,
 212       <span class="citerefentry"><span class="refentrytitle">named</span>(8)</span>.
 213     </p>
 214 </div>
 215 </div></body>
 216 </html>