1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
|
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta http-equiv="Content-Language" content="en" />
<title>s6-dns: the s6-dnsname program</title>
<meta name="Description" content="s6-dns: the s6-dnsname program" />
<meta name="Keywords" content="s6-dns client s6-dnsname dnsname domain name ip address ipv4 ipv6" />
<!-- <link rel="stylesheet" type="text/css" href="//skarnet.org/default.css" /> -->
</head>
<body>
<p>
<a href="index.html">s6-dns</a><br />
<a href="//skarnet.org/software/">Software</a><br />
<a href="//skarnet.org/">skarnet.org</a>
</p>
<h1> The s6-dnsname program </h1>
<p>
s6-dnsname finds the name associated to an IPv4 or IPv6 address.
</p>
<h2> Interface </h2>
<pre>
s6-dnsname [ -4 | -6 ] [ -H | -h ] [ -r ] [ -t <em>timeout</em> ] <em>ip</em>
</pre>
<ul>
<li> s6-dnsname converts the IP address <em>ip</em> to a name
ending in <tt>in-addr.arpa.</tt> or <tt>ip6.arpa.</tt> then makes a
PTR query for this name.
It waits for the result and prints the obtained names, one per line,
then exits 0. </li>
<li> If the domain exists but no relevant field has been found, it exits 1. </li>
<li> If the DNS answered but no answer is available, it prints a relevant
error message and exits 2. </li>
<li> By default, s6-dnsname looks for DNS cache addresses in the
<tt>/etc/resolv.conf</tt> file. If the DNSCACHEIP environment variable is set
and contains a list of IP (v4 or v6) addresses, separated by commas,
semicolons, spaces, tabs, newlines or carriage returns, then this list
is used instead. </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-4</tt> : interpret <em>ip</em> as an IPv4 address. </li>
<li> <tt>-6</tt> : interpret <em>ip</em> as an IPv6 address.
If neither of the <tt>-4</tt> and <tt>-6</tt> is given, or if both are
given, then <em>ip</em> will be interpreted as v4 or v6 depending on
its syntax. </li>
<li> <tt>-H</tt> : do not use data from <tt>/etc/hosts</tt>. This is
the default. </li>
<li> <tt>-h</tt> : use data from <tt>/etc/hosts</tt>, if available.
If there's a compiled <tt>/etc/hosts.cdb</tt> file that is newer than <tt>/etc/hosts</tt>,
it will be used instead. (See
<a href="s6-dns-hosts-compile.html">s6-dns-hosts-compile</a> for details.)
If the lookup in the hosts database returns at least one result, then
no DNS lookup is performed. </li>
<li> <tt>-r</tt> : random. By default, the program does not sort the
result, but prints them in the order received from the DNS. With this
option, it performs a random permutation on the results before printing
them. </li>
<li> <tt>-t</tt> <em>timeout</em> : if the resolution takes more
than <em>timeout</em> milliseconds, then it exits 99 right away with an error
message. By default, <em>timeout</em> is 0, which means no timeout. </li>
</ul>
<h2> Notes </h2>
<ul>
<li> If the underlying skalibs has been compiled with IPv6 support disabled,
s6-dnsname will not be able to use IPv6 transport for its resolution, but it
will still accept and resolve IPv6 addresses. </li>
</ul>
</body>
</html>
|
