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0N/A<
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th></
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0N/A<
div class="refentry">
0N/A<
div class="refnamediv">
0N/A<
p>host — DNS lookup utility</
p>
0N/A<
div class="refsynopsisdiv">
0N/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>
0N/A<
div class="refsection">
0N/A<
a name="id-1.14.3.7"></
a><
h2>DESCRIPTION</
h2>
0N/A<
p><
span class="command"><
strong>host</
strong></
span>
0N/A is a simple utility for performing DNS lookups.
0N/A It is normally used to convert names to IP addresses and vice versa.
0N/A When no arguments or options are given,
0N/A <
span class="command"><
strong>host</
strong></
span>
0N/A prints a short summary of its command line arguments and options.
0N/A<
p><
em class="parameter"><
code>name</
code></
em> is the domain name that is to be
0N/A up. It can also be a dotted-decimal IPv4 address or a colon-delimited
0N/A IPv6 address, in which case <
span class="command"><
strong>host</
strong></
span> will by
0N/A perform a reverse lookup for that address.
0N/A <
em class="parameter"><
code>server</
code></
em> is an optional argument which
0N/A the name or IP address of the name server that <
span class="command"><
strong>host</
strong></
span>
0N/A should query instead of the server or servers listed in
0N/A<
div class="refsection">
0N/A<
a name="id-1.14.3.8"></
a><
h2>OPTIONS</
h2>
0N/A<
div class="variablelist"><
dl class="variablelist">
0N/A<
dt><
span class="term">-4</
span></
dt>
0N/A Use IPv4 only for query transport.
0N/A See also the <
code class="option">-6</
code> option.
0N/A<
dt><
span class="term">-6</
span></
dt>
0N/A Use IPv6 only for query transport.
0N/A See also the <
code class="option">-4</
code> option.
0N/A<
dt><
span class="term">-a</
span></
dt>
0N/A "All". The <
code class="option">-a</
code> option is normally equivalent
0N/A to <
code class="option">-v -t <
code class="literal">ANY</
code></
code>.
0N/A It also affects the behaviour of the <
code class="option">-l</
code>
0N/A<
dt><
span class="term">-c <
em class="replaceable"><
code>class</
code></
em></
span></
dt>
0N/A Query class: This can be used to lookup HS (Hesiod) or CH
0N/A (Chaosnet) class resource records. The default class is IN
0N/A<
dt><
span class="term">-C</
span></
dt>
0N/A Check consistency: <
span class="command"><
strong>host</
strong></
span> will query the
0N/A SOA records for zone <
em class="parameter"><
code>name</
code></
em> from all
0N/A the listed authoritative name servers for that zone. The
0N/A list of name servers is defined by the NS records that are
0N/A<
dt><
span class="term">-d</
span></
dt>
0N/A Print debugging traces.
0N/A Equivalent to the <
code class="option">-v</
code> verbose option.
0N/A<
dt><
span class="term">-i</
span></
dt>
0N/A Use the
IP6.INT domain for reverse lookups of IPv6
0N/A addresses as defined in RFC1886 and deprecated in RFC4159.
0N/A The default is to use
IP6.ARPA as specified in RFC3596.
0N/A<
dt><
span class="term">-l</
span></
dt>
0N/A The <
span class="command"><
strong>host</
strong></
span> command performs a zone transfer of
0N/A zone <
em class="parameter"><
code>name</
code></
em> and prints out the NS,
0N/A Together, the <
code class="option">-l -a</
code>
0N/A options print all records in the zone.
0N/A<
dt><
span class="term">-N <
em class="replaceable"><
code>ndots</
code></
em></
span></
dt>
0N/A The number of dots that have to be
0N/A in <
em class="parameter"><
code>name</
code></
em> for it to be considered
0N/A absolute. The default value is that defined using the
0N/A or 1 if no ndots statement is present. Names with fewer
0N/A dots are interpreted as relative names and will be
0N/A searched for in the domains listed in
0N/A the <
span class="type">search</
span> or <
span class="type">domain</
span> directive
0N/A<
dt><
span class="term">-r</
span></
dt>
0N/A Non-recursive query:
0N/A Setting this option clears the RD (recursion desired) bit
0N/A in the query. This should mean that the name server
0N/A receiving the query will not attempt to
0N/A resolve <
em class="parameter"><
code>name</
code></
em>.
0N/A The <
code class="option">-r</
code> option
0N/A enables <
span class="command"><
strong>host</
strong></
span> to mimic the behavior of a
0N/A name server by making non-recursive queries and expecting
0N/A to receive answers to those queries that can be
0N/A referrals to other name servers.
0N/A<
dt><
span class="term">-R <
em class="replaceable"><
code>number</
code></
em></
span></
dt>
0N/A Number of retries for UDP queries:
0N/A If <
em class="parameter"><
code>number</
code></
em> is negative or zero, the
0N/A number of retries will default to 1. The default value is
0N/A 1, or the value of the <
em class="parameter"><
code>attempts</
code></
em>
0N/A<
dt><
span class="term">-s</
span></
dt>
0N/A Do <
span class="emphasis"><
em>not</
em></
span> send the query to the next
0N/A nameserver if any server responds with a SERVFAIL
0N/A response, which is the reverse of normal stub resolver
0N/A<
dt><
span class="term">-t <
em class="replaceable"><
code>type</
code></
em></
span></
dt>
0N/A The <
em class="parameter"><
code>type</
code></
em> argument can be any
0N/A recognized query type: CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc.
0N/A When no query type is specified, <
span class="command"><
strong>host</
strong></
span>
0N/A automatically selects an appropriate query type. By default, it
0N/A looks for A, AAAA, and MX records.
0N/A If the <
code class="option">-C</
code> option is given, queries will
0N/A be made for SOA records.
0N/A If <
em class="parameter"><
code>name</
code></
em> is a dotted-decimal IPv4
0N/A address or colon-delimited IPv6
0N/A address, <
span class="command"><
strong>host</
strong></
span> will query for PTR
0N/A If a query type of IXFR is chosen the starting serial
0N/A number can be specified by appending an equal followed by
0N/A the starting serial number
0N/A (like <
code class="option">-t <
code class="literal">IXFR=12345678</
code></
code>).
0N/A<
dt><
span class="term">-T</
span></
dt>
0N/A By default, <
span class="command"><
strong>host</
strong></
span> uses UDP when making
0N/A queries. The <
code class="option">-T</
code> option makes it use a TCP
0N/A connection when querying the name server. TCP will be
0N/A automatically selected for queries that require it, such
0N/A as zone transfer (AXFR) requests.
0N/A<
dt><
span class="term">-m <
em class="replaceable"><
code>flag</
code></
em></
span></
dt>
0N/A Memory usage debugging: the flag can
0N/A be <
em class="parameter"><
code>record</
code></
em>, <
em class="parameter"><
code>usage</
code></
em>,
0N/A or <
em class="parameter"><
code>trace</
code></
em>. You can specify
0N/A the <
code class="option">-m</
code> option more than once to set
0N/A<
dt><
span class="term">-v</
span></
dt>
0N/A Equivalent to the <
code class="option">-d</
code> debug option.
0N/A Verbose output can also be enabled by setting
0N/A the <
em class="parameter"><
code>debug</
code></
em> option
0N/A<
dt><
span class="term">-V</
span></
dt>
0N/A Print the version number and exit.
0N/A<
dt><
span class="term">-w</
span></
dt>
0N/A Wait forever: The query timeout is set to the maximum possible.
0N/A See also the <
code class="option">-W</
code> option.
0N/A<
dt><
span class="term">-W <
em class="replaceable"><
code>wait</
code></
em></
span></
dt>
0N/A Timeout: Wait for up to <
em class="parameter"><
code>wait</
code></
em>
0N/A seconds for a reply. If <
em class="parameter"><
code>wait</
code></
em> is
0N/A less than one, the wait interval is set to one second.
0N/A By default, <
span class="command"><
strong>host</
strong></
span> will wait for 5
0N/A seconds for UDP responses and 10 seconds for TCP
0N/A connections. These defaults can be overridden by
0N/A the <
em class="parameter"><
code>timeout</
code></
em> option
0N/A See also the <
code class="option">-w</
code> option.
0N/A<
div class="refsection">
0N/A<
a name="id-1.14.3.9"></
a><
h2>IDN SUPPORT</
h2>
0N/A If <
span class="command"><
strong>host</
strong></
span> has been built with IDN (internationalized
0N/A domain name) support, it can accept and display non-ASCII domain names.
0N/A <
span class="command"><
strong>host</
strong></
span> appropriately converts character encoding of
0N/A domain name before sending a request to DNS server or displaying a
0N/A reply from the server.
0N/A If you'd like to turn off the IDN support for some reason, defines
0N/A the <
code class="envar">IDN_DISABLE</
code> environment variable.
0N/A The IDN support is disabled if the variable is set when
0N/A <
span class="command"><
strong>host</
strong></
span> runs.
0N/A<
div class="refsection">
0N/A<
a name="id-1.14.3.10"></
a><
h2>FILES</
h2>
0N/A<
div class="refsection">
0N/A<
a name="id-1.14.3.11"></
a><
h2>SEE ALSO</
h2>
0N/A<
p><
span class="citerefentry"><
span class="refentrytitle">dig</
span>(1)</
span>,
0N/A <
span class="citerefentry"><
span class="refentrytitle">named</
span>(8)</
span>.
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