Help with keys...

[jtb1492]

Can sombody explain keys to me? I get that keys %hash returns an array with the key values. But how do I use keys when I have a hash of hashes? How do I find the second set of keys? I'm very new to perl so please be simple in you responses. Thanks, guys.

 

[TonyGroves]

A hash of hashes consists of an outer hash and many inner hashes. To get the keys of the outer hash, you would use:[tt]
@k=keys %outerhash;[/tt]
To get the keys of an inner hash, you would use:[tt]
@k=keys %{$outerhash{'innerhash'}};[/tt]
$outerhash{'innerhash'} represents the value of an element of $outerhash, but that value happens to be a hash, so you can then cast it as a hash by putting it inside %{...} and get its keys.

 

[mlibeson]

foreach $keylevel2 (keys %{$hash{$keylevel1}}) {
print $hash{$keylevel1}{$keylevel2}, "\n";
}


Michael Libeson

 

[KevinADC]

I get that keys %hash returns an array with the key values.

It depends on the context you use. If you use:

$num = keys %hash;

you get the number of keys in the hash,

if you use:

@keys = keys %hash;

you get a list of the value of the keys