getting the sort keys from a hash - perl

Question

This is the data dumper of \%spec_hash.
It is sorted by group which is a national exchange - and symbol.
foohost:~/walt $ vi /tmp/footoo
$VAR1 = {
'ARCX' => {
'IACI' => 1,
'MCHP' => 1,
},
'AMXO' => {
'YUM' => 1,
'SYK' => 1,
},
'XISX' => {
'FCEL' => 1,
'GPS' => 1,
}
};
I was trying to sort by keys these two hashes but cannot. For debugging purposes I really want to see what is getting pumped out of these hashes
foreach my $exch (sort keys %spec_hash) {
foreach my $exch (sort keys %{$spec_hash{$exch}}) {
If I comment out the dumper and try a regular sort :
#print Dumper(\%spec_hash) ;
foreach my $exch (sort keys %spec_hash) {
#foreach my $exch (sort keys %{$spec_hash{$exch}}) {
print "key: $exch, value: $spec_hash{$exch}\n"
}
this i what I get :
key: AMXO, value: HASH(0x9cc88a4)
key: ARCX, value: HASH(0x9cd6f1c)
key: XISX, value: HASH(0x9cbd5f0)
and trying to print this prints nothing at all :
foreach my $exch (sort keys %{$spec_hash{$exch}}) {
print "key: $exch, value: $spec_hash{$exch}\n"
}

Answer 1

If I understand correctly,
for my $exch (sort keys %spec_hash) {
for my $sym (sort keys %{ $spec_hash{$exch} }) {
print "Exchange: $exch, Symbol: $sym\n";
}
}
You want to loop over every symbol, but they are grouped by exchange, so you must first loop over the exchanges.

Answer 2

Data::Dumper doesn't sort its output by default.
Try adding $Data::Dumper::Sortkeys = 1; to your script.
use strict;
use warnings;
use Data::Dumper;
my %hash = (
'ARCX' => { 'IACI' => 1, 'MCHP' => 1, },
'AMXO' => { 'YUM' => 1, 'SYK' => 1, },
'XISX' => { 'FCEL' => 1, 'GPS' => 1, },
);
print do {
local $Data::Dumper::Sortkeys = 1;
Dumper \%hash;
};
Outputs:
$VAR1 = {
'AMXO' => {
'SYK' => 1,
'YUM' => 1
},
'ARCX' => {
'IACI' => 1,
'MCHP' => 1
},
'XISX' => {
'FCEL' => 1,
'GPS' => 1
}
};
Note: This can be modified to include a sort subroutine that you define