: The last_lowest is the last value written out to the file.
: The tmp value is the current value plucked from the list.
: My hope by going through all the values and picking every one that
: is larger than the last smallest one, the next one will be grabbed.
:
: By the way, I can't get Perl's sort function to do the right thing
: exactly either.
:
: my @sorted_ips=sort {$a <=> $b} @ip_list;
:
: This command sorts the first octet correctly, but not the second,
: third, or fourth octets. The numbers are in binary format when
: sort is run on them.
You have said in several posts that you want to sort them in binary
order. I'm really not sure what that means, but I understand you to
mean that you wish to use the integer representation for sorting
your prefixes.
You could (as somebody had pointed out earlier) use the Net::IP
module, which provides quite a few features. If you want only
sorted IPs, there are some venerable tools at your disposal. I
would suggest using the inet_aton call to turn the IP into a number.
#! /usr/bin/perl
#
# -- sort IPs by integer representation
use strict;
use Socket;
my @ips = readline(STDIN); # -- slurp
chomp(@ips);
@ips =
map { $_->[1] } # -- get second list elem
sort { $a->[0] <=> $b->[0] } # -- sort on first list elem
map { [ unpack( "N", inet_aton( $_ ) ), $_ ] } # -- make IP an integer
@ips;
print join("\n",@ips),"\n";
# -- end of file
Above is a so-called Schwartzian transform on a small list of IPs
(up to a few hundred thousand should be trivial. I ran the above on
a set of 15 million IPs I had sitting around which required about
9GB of RAM to run. The above snippet will not win any efficiency
prizes, but it should accomplish what you want.
: I don't undersand the special syntax on the sort command, but I
: suspect that I need something different there.
: The beauty of the sort function, if it will work, is that I can
: replace an entire function that is fairly long in comparison.
: This is why I'm using perl after all, it is supposed to be
: designed to do this sort of thing.
The usage of $a and $b in the sort function isn't intuitive--you
could say it's almost weird, but it is pretty powerful. If you
haven't already, try 'perldoc -f sort'. There are quite a few
examples.
-Martin
--
Martin A. Brown
http://linux-ip.net/
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