Access the Keys of a Hash Reference Without a For Loop

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

Hello Monks,

I have been needing your help a lot lately. This is a followup question to Is Using Threads Slower Than Not Using Threads?. I am trying to optimize my code to deal with a large list of ip addresses against a large text file.

Could you please school me on how to access the keys of a hash reference without using a for loop? I thought exists $ipsAll->{key}) was the way, but that appears to be how to access the values of the keys.

use warnings;
use strict;
use Regexp::Common qw /net/;

my $fw_file = 'tmp.log';

my @allIps = qw(10.8.1.5 10.8.1.6 10.8.1.7);
my %ipsMatch = map {$_ => 1} @allIps;
my @infectedIps = check_fw_logs(\%ipsMatch, $fw_file);

sub check_fw_logs { 

 # Sample Line to match
 Oct 31 23:58:12 x.x.x.x Oct 31 2010 23:58:14: 
<br>%PIX-5-106100: access-list INBOUND denied udp 
<br>outside/10.158.53.2(12143) -> dmz/192.168.19.11(53)
<br> hit-cnt 8 300-second interval [0x6be0682a, 0x0]
 
 my $ipsAll, $file = @_;
 my (@infectedIps);

 open (FILE, $file) or croak("Can't open $file: $!\n");
 while(<FILE>){
  my $sub = substr($_, 105, 40);
  if ($sub =~ /(\d+\.\d+\.\d+\.\d+)\(?:\d+\) -> 
outside\/(\d+\.\d+\.\d+\.\d+)/ && exists $ipsAll->{$1}){
    push(@infectedIps,$1);
  }
 }
 return @infectedIps;
}
[download]

Thanks,
Dru

Perl, the Leatherman of Programming languages. - qazwart

Comment on Access the Keys of a Hash Reference Without a For Loop Select or Download Code

Replies are listed 'Best First'.
Re: Access the Keys of a Hash Reference Without a For Loop by umasuresh (Hermit) on Nov 01, 2010 at 17:47 UTC
I am not sure if this is what you are looking for: `my @keys = keys %{$hash_ref};` [download]	[reply] [d/l]
Re: Access the Keys of a Hash Reference Without a For Loop by wink (Scribe) on Nov 01, 2010 at 18:28 UTC
exists $ipsAll->{$key} will return 1 (true) if the key exists. If you need to get a list of the keys, umasuresh's answer is what you want. Also, be careful about using exists on nested hash references, since the -> operator will create intervening values. `my %hash = ('foo' => 'foo'); my $ref = \%hash; print exists $ref->{'foo'}; #Prints 1 (true) print exists $ref->{'bar'}->{'baz'}; #Prints nothing (false) print exists $ref->{'bar'}; #Prints 1 (true)` [download]	[reply] [d/l]
Re^2: Access the Keys of a Hash Reference Without a For Loop by Dru (Hermit) on Nov 01, 2010 at 18:44 UTC
Thanks wink, I was just about to post to say I realized my code was actually correct and it will print out 1 (meaning it's true) if there was a match, basically what you said. Thanks, Dru Perl, the Leatherman of Programming languages. - qazwart	[reply] [d/l]
Re: Access the Keys of a Hash Reference Without a For Loop by Jim (Curate) on Nov 01, 2010 at 17:58 UTC
#!perl use strict; use warnings; my $state_capital_of; $state_capital_of->{'Alabama'} = 'Montgomery'; $state_capital_of->{'Alaska'} = 'Juneau'; $state_capital_of->{'Arizona'} = 'Phoenix'; $state_capital_of->{'Arkansas'} = 'Little Rock'; $state_capital_of->{'California'} = 'Sacramento'; print "$state_capital_of->{'Alabama'}\n"; print "$state_capital_of->{'Alaska'}\n"; print "$state_capital_of->{'Arizona'}\n"; print "$state_capital_of->{'Arkansas'}\n"; my $state = 'California'; print "$state_capital_of->{$state}\n" if exists $state_capital_of->{$state}; [download] This prints Montgomery Juneau Phoenix Little Rock Sacramento	[reply] [d/l]


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Access the Keys of a Hash Reference Without a For Loop

Montgomery Juneau Phoenix Little Rock Sacramento