IRIX Base Documentation 2001 May/SGI IRIX Base Documentation 2001 May.iso/usr/share/catman/p_man/cat3/perl5/Net::netent.z/Net::netent

Text File | 1998-10-30 | 5.0 KB | 199 lines

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     Net::netent - by-name interface to Perl's built-in getnet*() functions

SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
      use Net::netent qw(:FIELDS);
      getnetbyname("loopback")               or die "bad net";
      printf "%s is %08X\n", $n_name, $n_net;

      use Net::netent;

      $n = getnetbyname("loopback")          or die "bad net";
      { # there's gotta be a better way, eh?
          @bytes = unpack("C4", pack("N", $n->net));
          shift @bytes while @bytes && $bytes[0] == 0;
      }
      printf "%s is %08X [%d.%d.%d.%d]\n", $n->name, $n->net, @bytes;


DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
     This module's default exports override the core _g_e_t_n_e_t_b_y_n_a_m_e() and
     _g_e_t_n_e_t_b_y_a_d_d_r() functions, replacing them with versions that return
     "Net::netent" objects.  This object has methods that return the similarly
     named structure field name from the C's netent structure from _n_e_t_d_b._h;
     namely name, aliases, addrtype, and net.  The aliases method returns an
     array reference, the rest scalars.

     You may also import all the structure fields directly into your namespace
     as regular variables using the :FIELDS import tag.  (Note that this still
     overrides your core functions.)  Access these fields as variables named
     with a preceding n_.  Thus, $net_obj->_n_a_m_e() corresponds to $n_name if
     you import the fields.  Array references are available as regular array
     variables, so for example @{ $net_obj->_a_l_i_a_s_e_s() } would be simply
     @n_aliases.

     The _g_e_t_n_e_t() funtion is a simple front-end that forwards a numeric
     argument to _g_e_t_n_e_t_b_y_a_d_d_r(), and the rest to _g_e_t_n_e_t_b_y_n_a_m_e().

     To access this functionality without the core overrides, pass the use an
     empty import list, and then access function functions with their full
     qualified names.  On the other hand, the built-ins are still available
     via the CORE:: pseudo-package.

EEEEXXXXAAAAMMMMPPPPLLLLEEEESSSS
     The _g_e_t_n_e_t() functions do this in the Perl core:

         sv_setiv(sv, (I32)nent->n_net);

     The _g_e_t_h_o_s_t() functions do this in the Perl core:

         sv_setpvn(sv, hent->h_addr, len);

     That means that the address comes back in binary for the host functions,



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     and as a regular perl integer for the net ones.  This seems a bug, but
     here's how to deal with it:

      use strict;
      use Socket;
      use Net::netent;

      @ARGV = ('loopback') unless @ARGV;

      my($n, $net);

      for $net ( @ARGV ) {

          unless ($n = getnetbyname($net)) {
             warn "$0: no such net: $net\n";
             next;
          }

          printf "\n%s is %s%s\n",
                 $net,
                 lc($n->name) eq lc($net) ? "" : "*really* ",
                 $n->name;

          print "\taliases are ", join(", ", @{$n->aliases}), "\n"
                     if @{$n->aliases};

          # this is stupid; first, why is this not in binary?
          # second, why am i going through these convolutions
          # to make it looks right
          {
             my @a = unpack("C4", pack("N", $n->net));
             shift @a while @a && $a[0] == 0;
             printf "\taddr is %s [%d.%d.%d.%d]\n", $n->net, @a;
          }

          if ($n = getnetbyaddr($n->net)) {
             if (lc($n->name) ne lc($net)) {
                 printf "\tThat addr reverses to net %s!\n", $n->name;
                 $net = $n->name;
                 redo;
             }
          }
      }


NNNNOOOOTTTTEEEE
     While this class is currently implemented using the Class::Struct module
     to build a struct-like class, you shouldn't rely upon this.







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AUTHOR
     Tom Christiansen





















































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