How to build a Perl multidimensional array or hash? - arrays

Question

I have a set of CSV values like this:
device name, CPU value, frequency of CPU value, CPU in percentage
For example
router1,5,10,4
router1,5,1,5
router2,5,10,4
router2,5,2,5
router3,4,5,6
router3,7,6,5
I need to form a data structure like this:
array = {
router1 => [5,10,4],[5,1,5],
router2 => [5,10,4],[5,2,5],
router3 => [4,5,6],[7,6,5]
}
I need help in forming this data structure in Perl.
I have tried visualizing how to do this but am unable to do so. I would appreciate any help on this.
The end goal for me is to convert this into a JSON object.

Answer 1

This should get you started. It uses the DATA file handle so that I could embed the data in the program itself. I have used to_json from the JSON module to format the hash as JSON data. The statement $_ += 0 for #values converts the contents of #values from string to to numeric, to avoid quotation marks in the resultant JSON data.
use strict;
use warnings;
use JSON;
my %data;
while (<DATA>) {
chomp;
my ($device, #values) = split /,/;
$_ += 0 for #values;
push #{ $data{$device} }, \#values;
}
print to_json(\%data, { pretty => 1, canonical => 1 });
__DATA__
router1,5,10,4
router1,5,1,5
router2,5,10,4
router2,5,2,5
router3,4,5,6
router3,7,6,5
output
{
"router1" : [
[
5,
10,
4
],
[
5,
1,
5
]
],
"router2" : [
[
5,
10,
4
],
[
5,
2,
5
]
],
"router3" : [
[
4,
5,
6
],
[
7,
6,
5
]
]
}

Answer 2

Here is a simple solution which prints desired JSON object.
#!/usr/bin/env perl
use strict;
use warnings;
use 5.010;
my %hash;
while (my $line = <DATA>) {
chomp $line;
my ($device, #cpu_values) = split(/,/, $line);
my $cpu_token = join(",", #cpu_values);
$hash{$device} .= '[' . $cpu_token . '], ';
}
my #devices = keys %hash;
print "array = { \n";
foreach (sort #devices) {
print "$_ => [$hash{$_}]\n";
}
print "}\n";
__DATA__
router1,5,10,4
router1,5,1,5
router2,5,10,4
router2,5,2,5
router3,4,5,6
router3,7,6,5

Answer 3

In Perl you need to use references in the way of anonymous arrays and hashes to make multidimensional arrays, arrays of arrays, hashes containing hashes and anywhere in between. perlreftut should cover how to accomplish what you are trying to do. Here is an example I wrote the other day that could help explain as well:
print "\nFun with multidimensional arrays\n";
my #myMultiArray = ([1,2,3],[1,2,3],[1,2,3]);
for my $a (#myMultiArray){
for my $b (#{$a}){
print "$b\n";
}
}
print "\nFun with multidimensional arrays containing hashes\nwhich contains an anonymous array\n";
my #myArrayFullOfHashes = (
{'this-key'=>'this-value','that-key'=>'that-value'},
{'this-array'=>[1,2,3], 'this-sub' => sub {return 'hi'}},
);
for my $a (#myArrayFullOfHashes){
for my $b (keys %{$a}){
if (ref $a->{$b} eq 'ARRAY'){
for my $c (#{$a->{$b}}){
print "$b.$c => $c\n";
}
} elsif ($a->{$b} =~ /^CODE/){
print "$b => ". $a->{$b}() . "\n";
} else {
print "$b => $a->{$b}\n";
}
}
}