Do I have to explicitly tell keys() that the hash in my hash of hashes is a hash?

donfreenut has asked for the wisdom of the Perl Monks concerning the following question:

I have a hash of hashes. It looks like this:

my %servers = (
    BOUVET => {
        ps3_path => '\\\\BOUVET\\resin-2.0.3\\doc\\ps3\\',
        resin_path => '\\\\BOUVET\\resin-2.0.3\\',
        contexts_path => '\\\\BOUVET\\resin-2.0.3\\doc\\ps3\\contexts\
+\',
        customizations => {
            some_key => 'some data',
            another_key => 'more data'
        }
    }
);
[download]

I want to get at all the key/value pairs in the customizations hash. I'm trying this:

foreach my $customization (keys $servers{BOUVET}{customizations}) {
        print "$customization\n";
    }
[download]

and Perl is telling me that:

Type of arg 1 to keys must be hash (not hash element) at C:\deployment\newscripts\deploy-internal.pl line 102, near "}) "

which isn't cool. Do I have to somehow tell the keys function that $servers{BOUVET}{customizations} is itself a hash?

Muchas gracias...

---
donfreenut

Comment on Do I have to explicitly tell keys() that the hash in my hash of hashes is a hash? Select or Download Code

Replies are listed 'Best First'.
Re: Do I have to explicitly tell keys() that the hash in my hash of hashes is a hash? by runrig (Abbot) on Dec 07, 2001 at 23:48 UTC
In short, the answer is 'yes': `foreach my $customization (keys %{$servers{BOUVET}{customizations}}) {` [download] The long answer, and recommended reading, is perldoc perlref, perldsc, perllol, and perlreftut (the last one comes with 5.6 so is not on this site).	[reply] [d/l]
Re: Do I have to explicitly tell keys() that the hash in my hash of hashes is a hash? by lestrrat (Deacon) on Dec 07, 2001 at 23:49 UTC
`%servers <- that's a hash $servers{ BOUVET } <- that's a ref to a hash $server{ BOUVET }{ customizations } <- that's another ref to a hash` [download] keys() expets a hash as its value, not a ref to a hash. so you need to dereference it: `keys %{ $server{ BOUVET }{ customizations } }` [download]	[reply] [d/l] [select]
Re: Do I have to explicitly tell keys() that the hash in my hash of hashes is a hash? by dragonchild (Archbishop) on Dec 07, 2001 at 23:48 UTC
Try doing something like: `foreach my $customization (keys %{$serverse{BOUVET}{customizations}}) +{` [download] You have a hashref, so you need to tell Perl to dereference the hashref. ------ We are the carpenters and bricklayers of the Information Age. Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.	[reply] [d/l]
Re: Do I have to explicitly tell keys() that the hash in my hash of hashes is a hash? by demerphq (Chancellor) on Dec 07, 2001 at 23:51 UTC
Yes you do need to explicitly tell keys its a hash. Annoying at times, but necessary. `use strict; use warnings; my $hash={a=>{b=>1},c=>{d=>1}}; foreach my $key (keys %$hash) { print "$key\n"; foreach my $subkey (keys %{$hash->{$key}}) { print "\t$subkey\n"; } }` [download] So theres the simple way and the complicated way... HTH Yves / DeMerphq -- This space for rent.	[reply] [d/l]