mingw/html/lib/Net/netent.html

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   5 <title>Net::netent - by-name interface to Perl's built-in getnet* functions</title>
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  13 <big><strong><span class="block">&nbsp;Net::netent - by-name interface to Perl's built-in getnet* functions</span></strong></big>
  14 </td></tr>
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  16
  17 <p><a name="__index__"></a></p>
  18 <!-- INDEX BEGIN -->
  19
  20 <ul>
  21
  22         <li><a href="#name">NAME</a></li>
  23         <li><a href="#synopsis">SYNOPSIS</a></li>
  24         <li><a href="#description">DESCRIPTION</a></li>
  25         <li><a href="#examples">EXAMPLES</a></li>
  26         <li><a href="#note">NOTE</a></li>
  27         <li><a href="#author">AUTHOR</a></li>
  28 </ul>
  29 <!-- INDEX END -->
  30
  31 <hr />
  32 <p>
  33 </p>
  34 <h1><a name="name">NAME</a></h1>
  35 <p>Net::netent - by-name interface to Perl's built-in getnet*() functions</p>
  36 <p>
  37 </p>
  38 <hr />
  39 <h1><a name="synopsis">SYNOPSIS</a></h1>
  40 <pre>
  41  use Net::netent qw(:FIELDS);
  42  getnetbyname(&quot;loopback&quot;)               or die &quot;bad net&quot;;
  43  printf &quot;%s is %08X\n&quot;, $n_name, $n_net;</pre>
  44 <pre>
  45  use Net::netent;</pre>
  46 <pre>
  47  $n = getnetbyname(&quot;loopback&quot;)          or die &quot;bad net&quot;;
  48  { # there's gotta be a better way, eh?
  49      @bytes = unpack(&quot;C4&quot;, pack(&quot;N&quot;, $n-&gt;net));
  50      shift @bytes while @bytes &amp;&amp; $bytes[0] == 0;
  51  }
  52  printf &quot;%s is %08X [%d.%d.%d.%d]\n&quot;, $n-&gt;name, $n-&gt;net, @bytes;</pre>
  53 <p>
  54 </p>
  55 <hr />
  56 <h1><a name="description">DESCRIPTION</a></h1>
  57 <p>This module's default exports override the core <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_getnetbyname"><code>getnetbyname()</code></a> and
  58 <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_getnetbyaddr"><code>getnetbyaddr()</code></a> functions, replacing them with versions that return
  59 ``Net::netent'' objects.  This object has methods that return the similarly
  60 named structure field name from the C's netent structure from <em>netdb.h</em>;
  61 namely name, aliases, addrtype, and net.  The aliases
  62 method returns an array reference, the rest scalars.</p>
  63 <p>You may also import all the structure fields directly into your namespace
  64 as regular variables using the :FIELDS import tag.  (Note that this still
  65 overrides your core functions.)  Access these fields as variables named
  66 with a preceding <code>n_</code>.  Thus, <code>$net_obj-&gt;name()</code> corresponds to
  67 $n_name if you import the fields.  Array references are available as
  68 regular array variables, so for example <code>@{ $net_obj-&gt;aliases()
  69 }</code> would be simply @n_aliases.</p>
  70 <p>The <code>getnet()</code> function is a simple front-end that forwards a numeric
  71 argument to getnetbyaddr(), and the rest
  72 to getnetbyname().</p>
  73 <p>To access this functionality without the core overrides,
  74 pass the <a href="file://C|\msysgit\mingw\html/pod/perlfunc.html#item_use"><code>use</code></a> an empty import list, and then access
  75 function functions with their full qualified names.
  76 On the other hand, the built-ins are still available
  77 via the <code>CORE::</code> pseudo-package.</p>
  78 <p>
  79 </p>
  80 <hr />
  81 <h1><a name="examples">EXAMPLES</a></h1>
  82 <p>The <code>getnet()</code> functions do this in the Perl core:</p>
  83 <pre>
  84     sv_setiv(sv, (I32)nent-&gt;n_net);</pre>
  85 <p>The <code>gethost()</code> functions do this in the Perl core:</p>
  86 <pre>
  87     sv_setpvn(sv, hent-&gt;h_addr, len);</pre>
  88 <p>That means that the address comes back in binary for the
  89 host functions, and as a regular perl integer for the net ones.
  90 This seems a bug, but here's how to deal with it:</p>
  91 <pre>
  92  use strict;
  93  use Socket;
  94  use Net::netent;</pre>
  95 <pre>
  96  @ARGV = ('loopback') unless @ARGV;</pre>
  97 <pre>
  98  my($n, $net);</pre>
  99 <pre>
 100  for $net ( @ARGV ) {</pre>
 101 <pre>
 102      unless ($n = getnetbyname($net)) {
 103         warn &quot;$0: no such net: $net\n&quot;;
 104         next;
 105      }</pre>
 106 <pre>
 107      printf &quot;\n%s is %s%s\n&quot;,
 108             $net,
 109             lc($n-&gt;name) eq lc($net) ? &quot;&quot; : &quot;*really* &quot;,
 110             $n-&gt;name;</pre>
 111 <pre>
 112      print &quot;\taliases are &quot;, join(&quot;, &quot;, @{$n-&gt;aliases}), &quot;\n&quot;
 113                 if @{$n-&gt;aliases};</pre>
 114 <pre>
 115      # this is stupid; first, why is this not in binary?
 116      # second, why am i going through these convolutions
 117      # to make it looks right
 118      {
 119         my @a = unpack(&quot;C4&quot;, pack(&quot;N&quot;, $n-&gt;net));
 120         shift @a while @a &amp;&amp; $a[0] == 0;
 121         printf &quot;\taddr is %s [%d.%d.%d.%d]\n&quot;, $n-&gt;net, @a;
 122      }</pre>
 123 <pre>
 124      if ($n = getnetbyaddr($n-&gt;net)) {
 125         if (lc($n-&gt;name) ne lc($net)) {
 126             printf &quot;\tThat addr reverses to net %s!\n&quot;, $n-&gt;name;
 127             $net = $n-&gt;name;
 128             redo;
 129         }
 130      }
 131  }</pre>
 132 <p>
 133 </p>
 134 <hr />
 135 <h1><a name="note">NOTE</a></h1>
 136 <p>While this class is currently implemented using the Class::Struct
 137 module to build a struct-like class, you shouldn't rely upon this.</p>
 138 <p>
 139 </p>
 140 <hr />
 141 <h1><a name="author">AUTHOR</a></h1>
 142 <p>Tom Christiansen</p>
 143 <table border="0" width="100%" cellspacing="0" cellpadding="3">
 144 <tr><td class="block" style="background-color: #cccccc" valign="middle">
 145 <big><strong><span class="block">&nbsp;Net::netent - by-name interface to Perl's built-in getnet* functions</span></strong></big>
 146 </td></tr>
 147 </table>
 148
 149 </body>
 150
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