How to create a hash of arrays or hash of hashes - perl

Question

I have a file named Jobs.conf which contains:
JobName: A
JobSize: 100
JobArrival:1
JobExe:100
JobName: B
JobSize: 100
JobArrival:2
JobExe:100
JobName: C
JobSize: 100
JobArrival:3
JobExe:100
JobName: D
JobSize: 100
JobArrival:4
JobExe:100
Is it possible to read this file so each Job is stored in an array and then the 4 arrays are stored in a hash? Would it make more sense to store this as a hash of hashes and is that possible?

Answer 1

The key is to set $/ (the input record separator) properly:
This influences Perl's idea of what a "line" is. Works like awk's RS
variable, including treating empty lines as a terminator if set to the
null string (an empty line cannot contain any spaces or tabs). You may
set it to a multi-character string to match a multi-character
terminator, or to undef to read through the end of file. Setting it
to "\n\n" means something slightly different than setting to "",
if the file contains consecutive empty lines. Setting to "" will
treat two or more consecutive empty lines as a single empty line.
Setting to "\n\n" will blindly assume that the next input character
belongs to the next paragraph, even if it's a newline.
Then we just take advantage of how the records are laid out by split-ing directly into a hash reference:
use strict;
use warnings;
use Data::Dump;
local $/ = "";
my #jobs;
while (<DATA>) {
push(#jobs, {split(/:\s*|\n/)});
}
dd(\#jobs);
__DATA__
JobName: A
JobSize: 100
JobArrival:1
JobExe:100
JobName: B
JobSize: 100
JobArrival:2
JobExe:100
JobName: C
JobSize: 100
JobArrival:3
JobExe:100
JobName: D
JobSize: 100
JobArrival:4
JobExe:100
Or just:
my #jobs = map { {split(/:\s*|\n/)} } <DATA>;
Output:
[
{ JobArrival => 1, JobExe => 100, JobName => "A", JobSize => 100 },
{ JobArrival => 2, JobExe => 100, JobName => "B", JobSize => 100 },
{ JobArrival => 3, JobExe => 100, JobName => "C", JobSize => 100 },
{ JobArrival => 4, JobExe => 100, JobName => "D", JobSize => 100 },
]
An array of hashes (the previous example) would be my preference, but if you wanted a hash of hashes, you'd need to modify the code slightly:
my %jobs;
while (<DATA>) {
my %temp = split(/:\s*|\n/);
$jobs{delete($temp{JobName})} = \%temp;
}
dd(\%jobs);
Output:
{
A => { JobArrival => 1, JobExe => 100, JobSize => 100 },
B => { JobArrival => 2, JobExe => 100, JobSize => 100 },
C => { JobArrival => 3, JobExe => 100, JobSize => 100 },
D => { JobArrival => 4, JobExe => 100, JobSize => 100 },
}