Net::DNS answer count

g_speran has asked for the wisdom of the Perl Monks concerning the following question:

Hell Perl Monks,

Is there a way, in the code below, to print the number of answers returned for the query and reply sections, before printing the actual results? I'm sure there is but i am struggling to figure it out.

For the query section, I know my data is in $query->answer->rdatastr and i would like to get the total scalar count

For the reply section, I know the data is in $reply->answer->address and i would like to get the total scalar count

use warnings;
use strict;
use Net::DNS;
use Data::Dumper::Simple;

my $dnsserver;
my @resolver;

@resolver = qw(192.168.10.98);
foreach $dnsserver (@resolver) {
    print "\n\nValidating Entries against $dnsserver\n";
    my $resolver = Net::DNS::Resolver->new(
        nameservers =>$dnsserver,
        retry => 2,
        #recurse     => 0,
        #debug       => 1,
    );
    my $ip = "192.168.50.70";
    
    my $target_ip = join('.', reverse split(/\./, $ip)).".in-addr.arpa
+";

    my $query = $resolver->query($target_ip, 'PTR');
    my $reply = $resolver->search("garytest.fedlab.local",'A');
    warn Dumper(\$query, \$reply);
    if ($query) {
        # Print total count Here before Dispalying
        # Print "Total # of Hostnames found: ",(code) , "\n";
        print "\n\nHost names found......\n";
      foreach my $answer ($query->answer) {
        my $value=$answer->rdatastr;
        chop $value if ($value =~/.$/);
        print "\t", $value, "\n";
      }
    }
    else {
      print "\tReverse Lookup failed: ", $resolver->errorstring, "\n";
    }

    if ($reply) {
        # Print total count Here before Dispalying
        # Print "Total # of IP found: ",(code) , "\n"; #
        print "\n\nIP Address Found found......\n";
        foreach my $rr ($reply->answer) {
            print "\t", $rr->address, "\n";
    }
    } else {
            warn "\tForward Lookup Failed: ", $resolver->errorstring, 
+"\n";
    }
}
[download]

OUTPUT.......With Dumper

Z:\>perl net_dns.pl


Validating Entries against 192.168.10.98
$query = bless( {
                  'replyfrom' => '192.168.10.98',
                  'status' => 34176,
                  'authority' => [],
                  'answer' => [
                                bless( {
                                         'ptrdname' => bless( {
                                                                'label
+' => [
                                                                      
+       'garytest_dup3'
                                                                      
+     ]
                                                              }, 'Net:
+:DNS::DomainName1035' ),
                                         'owner' => bless( {
                                                             'label' =
+> [],
                                                             'origin' 
+=> bless( {
                                                                      
+            'label' => [
                                                                      
+                         '70',
                                                                      
+                         '50',
                                                                      
+                         '168',
                                                                      
+                         '192',
                                                                      
+                         'in-addr',
                                                                      
+                         'arpa'
                                                                      
+                       ]
                                                                      
+          }, 'Net::DNS::DomainName' )
                                                           }, 'Net::DN
+S::DomainName1035' ),
                                         'rdlength' => 15,
                                         'class' => 1,
                                         'type' => 12,
                                         'ttl' => 3600
                                       }, 'Net::DNS::RR::PTR' ),
                                bless( {
                                         'rdlength' => 23,
                                         'owner' => bless( {
                                                             'label' =
+> [],
                                                             'origin' 
+=> $query->{'answer'}[0]{'owner'}{'origin'}
                                                           }, 'Net::DN
+S::DomainName1035' ),
                                         'ttl' => 3600,
                                         'class' => 1,
                                         'type' => 12,
                                         'ptrdname' => bless( {
                                                                'label
+' => [
                                                                      
+       'garytest',
                                                                      
+       'fedlab',
                                                                      
+       'local'
                                                                      
+     ]
                                                              }, 'Net:
+:DNS::DomainName1035' )
                                       }, 'Net::DNS::RR::PTR' ),
                                bless( {
                                         'rdlength' => 16,
                                         'owner' => bless( {
                                                             'label' =
+> [],
                                                             'origin' 
+=> $query->{'answer'}[0]{'owner'}{'origin'}
                                                           }, 'Net::DN
+S::DomainName1035' ),
                                         'ttl' => 3600,
                                         'type' => 12,
                                         'class' => 1,
                                         'ptrdname' => bless( {
                                                                'origi
+n' => bless( {
                                                                      
+               'label' => [
                                                                      
+                            'fedlab',
                                                                      
+                            'local'
                                                                      
+                          ]
                                                                      
+             }, 'Net::DNS::DomainName' ),
                                                                'label
+' => [
                                                                      
+       'garytest_dup2'
                                                                      
+     ]
                                                              }, 'Net:
+:DNS::DomainName1035' )
                                       }, 'Net::DNS::RR::PTR' ),
                                bless( {
                                         'ptrdname' => bless( {
                                                                'origi
+n' => $query->{'answer'}[2]{'ptrdname'}{'origin'},
                                                                'label
+' => [
                                                                      
+       'garytest_dup4'
                                                                      
+     ]
                                                              }, 'Net:
+:DNS::DomainName1035' ),
                                         'ttl' => 3600,
                                         'class' => 1,
                                         'type' => 12,
                                         'rdlength' => 16,
                                         'owner' => bless( {
                                                             'origin' 
+=> $query->{'answer'}[0]{'owner'}{'origin'},
                                                             'label' =
+> []
                                                           }, 'Net::DN
+S::DomainName1035' )
                                       }, 'Net::DNS::RR::PTR' ),
                                bless( {
                                         'ttl' => 3600,
                                         'class' => 1,
                                         'type' => 12,
                                         'rdlength' => 14,
                                         'owner' => bless( {
                                                             'origin' 
+=> $query->{'answer'}[0]{'owner'}{'origin'},
                                                             'label' =
+> []
                                                           }, 'Net::DN
+S::DomainName1035' ),
                                         'ptrdname' => bless( {
                                                                'label
+' => [
                                                                      
+       'garytest_dup'
                                                                      
+     ]
                                                              }, 'Net:
+:DNS::DomainName1035' )
                                       }, 'Net::DNS::RR::PTR' )
                              ],
                  'question' => [
                                  bless( {
                                           'qclass' => 1,
                                           'qname' => bless( {
                                                               'label'
+ => [
                                                                      
+      '70',
                                                                      
+      '50',
                                                                      
+      '168',
                                                                      
+      '192',
                                                                      
+      'in-addr',
                                                                      
+      'arpa'
                                                                      
+    ]
                                                             }, 'Net::
+DNS::DomainName1035' ),
                                           'qtype' => 12
                                         }, 'Net::DNS::Question' )
                                ],
                  'count' => [
                               1,
                               5,
                               0,
                               0
                             ],
                  'additional' => [],
                  'id' => 55726,
                  'xedns' => bless( {
                                      'owner' => bless( {
                                                          'label' => [
+]
                                                        }, 'Net::DNS::
+DomainName1035' ),
                                      'type' => 41
                                    }, 'Net::DNS::RR::OPT' ),
                  'replysize' => 188
                }, 'Net::DNS::Packet' );
$reply = bless( {
                  'replysize' => 87,
                  'xedns' => bless( {
                                      'owner' => $query->{'xedns'}{'ow
+ner'},
                                      'type' => 41
                                    }, 'Net::DNS::RR::OPT' ),
                  'additional' => [],
                  'id' => 40872,
                  'count' => [
                               1,
                               3,
                               0,
                               0
                             ],
                  'question' => [
                                  bless( {
                                           'qtype' => 1,
                                           'qname' => bless( {
                                                               'label'
+ => [
                                                                      
+      'garytest',
                                                                      
+      'fedlab',
                                                                      
+      'local'
                                                                      
+    ]
                                                             }, 'Net::
+DNS::DomainName1035' ),
                                           'qclass' => 1
                                         }, 'Net::DNS::Question' )
                                ],
                  'authority' => [],
                  'answer' => [
                                bless( {
                                         'address' => '+�2G',
                                         'ttl' => 3600,
                                         'class' => 1,
                                         'type' => 1,
                                         'rdlength' => 4,
                                         'owner' => bless( {
                                                             'origin' 
+=> bless( {
                                                                      
+            'label' => [
                                                                      
+                         'garytest',
                                                                      
+                         'fedlab',
                                                                      
+                         'local'
                                                                      
+                       ]
                                                                      
+          }, 'Net::DNS::DomainName' ),
                                                             'label' =
+> []
                                                           }, 'Net::DN
+S::DomainName1035' )
                                       }, 'Net::DNS::RR::A' ),
                                bless( {
                                         'type' => 1,
                                         'class' => 1,
                                         'ttl' => 3600,
                                         'owner' => bless( {
                                                             'origin' 
+=> $reply->{'answer'}[0]{'owner'}{'origin'},
                                                             'label' =
+> []
                                                           }, 'Net::DN
+S::DomainName1035' ),
                                         'rdlength' => 4,
                                         'address' => '+�2F'
                                       }, 'Net::DNS::RR::A' ),
                                bless( {
                                         'rdlength' => 4,
                                         'owner' => bless( {
                                                             'origin' 
+=> $reply->{'answer'}[0]{'owner'}{'origin'},
                                                             'label' =
+> []
                                                           }, 'Net::DN
+S::DomainName1035' ),
                                         'ttl' => 3600,
                                         'type' => 1,
                                         'class' => 1,
                                         'address' => '+�2H'
                                       }, 'Net::DNS::RR::A' )
                              ],
                  'status' => 34176,
                  'replyfrom' => '192.168.10.98'
                }, 'Net::DNS::Packet' );


Host names found......
        garytest_dup3
        garytest.fedlab.local
        garytest_dup2.fedlab.local
        garytest_dup4.fedlab.local
        garytest_dup


IP Address Found found......
        192.168.50.71
        192.168.50.70
        192.168.50.72
[download]

Comment on Net::DNS answer count Select or Download Code

Replies are listed 'Best First'.
Re: Net::DNS answer count by kcott (Archbishop) on Apr 08, 2023 at 22:19 UTC
G'day g_speran, The values of both answer keys (`$query->{answer}` & `$reply->{answer}`) are arrayrefs. Counting the number of elements in an arrayref is very simple: `$ perl -E 'my $answer = [qw{x y z}]; say 0+@$answer;' 3` [download] You might benefit from reading "perldsc - Perl Data Structures Cookbook". — Ken	[reply] [d/l] [select]
Re^2: Net::DNS answer count by g_speran (Scribe) on Apr 08, 2023 at 23:55 UTC
So I got the code to work by doing the following: Is there a better way to do this with the code originally posted? `my $query = $resolver->query($target_ip, 'PTR'); my @answer = $query->answer; print "Total # of Hostnames found: ", scalar(@answer), "\n";` [download]	[reply] [d/l]
Re^3: Net::DNS answer count by kcott (Archbishop) on Apr 10, 2023 at 06:37 UTC
"Is there a better way to do this with the code originally posted?" In essence, no. You want the value of `@answer` in the loop just after reporting the count, so it makes sense to assign '`my @answer =`' once and then reuse the value. If you're asking specifically about the `print` statement, what you have is fine. There are multiple ways of doing this and, for the most part, it would come down to personal style more than anything else. I tend to favour '`0+@array`' over '`scalar(@array)`'; but that's just me. Here's a handful of different ways you could do this: `$ perl -E ' my @answers = qw{x y z}; say "Total: ", scalar(@answers); say "Total: ", 0+@answers; say "Total: @{[scalar @answers]}"; say "Total: @{[0+@answers]}"; ' Total: 3 Total: 3 Total: 3 Total: 3` [download] [See "discussion of @{[...]}" (from a few days ago) if you're unfamiliar with that construct.] In the main, your code is fine. There's one subtlety of which few are aware (or fully understand) — don't feel too bad about this slip-up by yourself. :-) The loop variable in a `for` loop is lexically scoped to that loop. Other references to variables of the same name outside the loop are different variables. Consider these (and note that I had to turn off `strict` for demonstration purposes): `$ perl -E ' #use strict; use warnings; { my $i; for $i (1,2,3) { say $i; } say $i // "undefined"; } { for my $i (1,2,3) { say $i; } say $i // "undefined"; } { for $i (1,2,3) { say $i; } say $i // "undefined"; } { my $i = q{completely different $i}; for $i (1,2,3) { say $i; } say $i // "undefined"; } ' 1 2 3 undefined 1 2 3 undefined 1 2 3 undefined 1 2 3 completely different $i` [download] With `strict` enabled, the `$i` outside the loop is problematic: `$ perl -E ' use strict; use warnings; for my $i (1,2,3) { say $i; } say $i // "undefined"; ' Global symbol "$i" requires explicit package name (did you forget to d +eclare "my $i"?) at -e line 9. Execution of -e aborted due to compilation errors.` [download] There is an anomaly with this. I consider it to be a bug in Perl and probably the cause of much confusion. If you don't declare the loop variable with `my`, `strict` complains: `$ perl -E ' use strict; use warnings; for $i (1,2,3) { say $i; } ' Global symbol "$i" requires explicit package name (did you forget to d +eclare "my $i"?) at -e line 5. Global symbol "$i" requires explicit package name (did you forget to d +eclare "my $i"?) at -e line 6. Execution of -e aborted due to compilation errors.` [download] unless you've previously declared a different variable with the same name with `my` in an outer scope: `$ perl -E ' use strict; use warnings; my $i; for $i (1,2,3) { say $i; } say $i // "undefined"; ' 1 2 3 undefined` [download] Declaration after the loop still raises an error with the loop variable: `$ perl -E ' use strict; use warnings; for $i (1,2,3) { say $i; } my $i; say $i // "undefined"; ' Global symbol "$i" requires explicit package name (did you forget to d +eclare "my $i"?) at -e line 5. Global symbol "$i" requires explicit package name (did you forget to d +eclare "my $i"?) at -e line 6. Execution of -e aborted due to compilation errors.` [download] Here's a very quick review of the remainder; bear in mind that much of this comes down to style as opposed to corrections: Using a plural for arrays generally reads better: `$answer` vs. `@answers`. Also, `@answer` could be a simple typo but `strict` won't pick up that you really meant `$answer`. Although `$object->method` is valid syntax, `$object->method()` is clearer in my opinion. You generally want chomp instead of chop. Don't bother `chomp`ing when the next line is `print` (now requiring that the newline be added back again). In other words, don't write all of this: `chomp $line; print $line, "\n";` [download] when this would've sufficed: `print $line;` [download] `for` and `foreach` are synonymous. Using the former promotes (good) laziness. Consistent code layout improves readability. What you have isn't terrible; although, I do see indentations of 2, 4, 5 & 8 characters. — Ken	[reply] [d/l] [select]
Re^4: Net::DNS answer count by g_speran (Scribe) on Apr 10, 2023 at 13:21 UTC