Re: Sort hash with values

[sundialsvc4]

I think that I see the problem.   Ordinarily, you would be able to iterate over something like foreach ( sort keys(%IP_store) ) ..., but IP-address strings of varying lengths won’t sort correctly as strings.

The sort verb does allow for a subroutine to be specified, which must return a value that is less than, equal or greater than zero as appropriate, so we do have the mechanism by which to sort the strings the way we want:   as a left-to-right hierarchical collection of four integers.   So, let’s define a separate sub to do this ... something along these (untested) lines:

# 'sort' COMPARISON FUNCTION FOR IP-ADDRESSES.
sub ip_compare {
   # GRAB THE TWO ARGUMENTS PASSED BY 'SORT'
   my ($a, $b) = @_;

   # SPLIT THE IP-ADDRESSES INTO FOUR =STRINGS= BY
   # THE PERIOD CHARACTER.
   my ($a1, $a2, $a3, $a4) = split('\.', @$a);
   my ($b1, $b2, $b3, $b4) = split('\.', @$b);

   # TYPECAST EACH COMPONENT AS INTEGERS, THEN
   # USE INTEGER '<=>' OPERATOR TO COMPARE NUMBERS.
   # USE A STACK OF SHORT-CIRCUIT '||' OPS WHICH WILL
   # STOP AT (AND RETURN) THE FIRST NON-ZERO RESULT
   # IN THE CHAIN.
   return 
      (int($a1) <=> int($b1))
   || (int($a2) <=> int($b2))
   || (int($a3) <=> int($b3))
   || (int($a4) <=> int($b4));
}

And I would put that subroutine (when debugged), with its comments, into my program.   There are many ways to write it:   this one is reasonably clear.

Now we can do something like sort (ip_compare, keys(%ip_addr)), or something like that, and it should work.   You iterate over the returned list of keys and retrieve the values from the hash by key.

[AnomalousMonk]

# SPLIT THE IP-ADDRESSES INTO FOUR =STRINGS= BY
# THE PERIOD CHARACTER.
my ($a1, $a2, $a3, $a4) = split('.', @$a);

The split built-in function does not use single-quotes around a  /PATTERN/ argument to 'meta-quote' the argument: the  '.' in the above really is trying to split on "any character except newline". Use  '\.' to split on a literal period.

>perl -wMstrict -le
"my $s = 'a.bb.ccc.d';
 ;;
 my @ra = split '.', $s;
 print 'naked dot';
 printf qq{  '$_'} for @ra;
 print '@ra elements: ', scalar @ra;
 ;;
 @ra = split '\.', $s;
 print 'escaped dot';
 printf qq{  '$_'} for @ra;
"
naked dot
@ra elements: 0
escaped dot
  'a'  'bb'  'ccc'  'd'