> I don't understand this line:
$ips{$source_ip}->{$dest_ip}++;
> how can you access and increment something that doesnt exist?
Fancy name: autovivification - perl, w/ your best interests at heart
(generally) knows what you want to do, so it automagically creates the
source_ip hash entry (if it doesn't exist), creates the anon-hash (ditto),
adds a dest_ip key (ibid) and sees the incr. op, so set a value to zero
and increments it - bingo
$ips{$source_ip}->{$dest_ip}++;
if ( $ips{$source_ip}->{$dest_ip} == 1 ) {
print "First time $source_ip has sent $dest_ip packets!\n";
}
On the other hand, autoV works for increment, but you should see a warning
(you are using -w/strict right?) if you try::
if ( $ips{$source_ip}->{$dest_ip} == 0 ) {
print "First time $source_ip has sent $dest_ip packets!\n";
}
$ips{$source_ip}->{$dest_ip}++;
Here, if it *is* the first time, as dest_ip doesn't exist, you'll see:
Use of uninitialized value in numeric eq (==) at ....
In this case:
unless ( $ips{$source_ip}->{$dest_ip} ) {
print "First time $source_ip has sent $dest_ip packets!\n";
}
$ips{$source_ip}->{$dest_ip}++;
gets around that as there's no compare - basically you're checking for
truth, existence or non-zero.
Make any sense?
a
Andy Bach, Sys. Mangler
Internet: [EMAIL PROTECTED]
VOICE: (608) 261-5738 FAX 264-5932
Hardware, n.:
The parts of a computer system that can be kicked.
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