Sort Hosts File With Perl

Recently I had to sort more than 100 thousand hosts alphabetically. The tricky part was that these were domains, and I wanted to sort them by top-level domain. Before you can use the script you need to install Domain::PublicSuffix.

The following perl script can do that. Just paste all the host names inside the script file as shown in the example below:

my @hosts = (

'zzztech.com',
'www.zzztech.com',
'zzzzzz.com',
'www.zzzzzz.com',

);

sort_hosts.pl

use feature qw( say state );
use Domain::PublicSuffix qw( );

sub get_sort_key {
  my ($host) = @_;
  $host =~ s/\.\z//;
  state $dps = Domain::PublicSuffix->new();
  $dps->get_root_domain($host)
  or die "$host: ".$dps->error();

  my @name= split /\./, substr($host, 0, -length($dps->suffix())-1);
  my @suffix = split /\./, $dps->suffix();
  return join '.', reverse @suffix, @name;
}

my @hosts = (

 'zzztech.com',
 'www.zzztech.com',
 'zzzzzz.com',
 'www.zzzzzz.com',

);

my @sorted_hosts = 
map s/^[^\0]*\0//r,
sort
map get_sort_key($_)."\0".$_,
@hosts;

say for @sorted_hosts;

Execute it with:

perl sort_hosts.pl

The sorted results will be displayed in the tty. To pipe to a new file type:

perl sort_hosts.pl > My_Sorted_Hosts.txt