Iterate over complex JSON

Northwood128 has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks! I'm new to Perl, and I was given the task of writing a new Nagios plug-in. I have a JSON file with the description of several services we need to check (via curl). Here is a sample of how the JSON file looks

{
    "services": [
        {
            "service": "serviceName1",
            "site": "www.example1.com",
            "uri": "http://www.url.com/index.html",
            "option": [
                {
                    "name": "option-a",
                    "server": "server-a",
                    "servers": ["server-a1", "server-a2", "server-a3",
+ "server-a4", "server-a5", "server-b6"]
                },
                {
                    "name": "option-b",
                    "lbvserver": "server-b",
                    "servers": ["server-b1", "server-b2", "server-b3",
+ "server-b4", "server-b5", "server-b6"]
                }
            ]
        },
        {
            "service": "serviceName2",
            "site": "www.example2.com",
            "uri": "http://www.url2.com/index.html",
            "option": [
                {
                    "name": "option-a",
                    "server": "server-a",
                    "servers": ["server-a1", "server-a2", "server-a3",
+ "server-a4", "server-a5", "server-b6"]
                },
                {
                    "name": "option-b",
                    "lbvserver": "server-b",
                    "servers": ["server-b1", "server-b2", "server-b3",
+ "server-b4", "server-b5", "server-b6"]
                }
            ]
        }
     ]
}
[download]

I managed myself to put that into a variable $config using the JSON module. Now, this is the portion of code that's not working.

my @service = $config->{'services'};
    foreach $oneservice (@service){
       print $oneservice{'service'};
    }
[download]

I don't want to actually print "serviceName1", or "serviceName2". I'm trying to get to the "servers" key inside "option". The thing is that I'm missing something. When i run this, i get this

Global symbol "%oneservice" requires explicit package name at ./script
+.pl line 102.
Execution of ./script.pl aborted due to compilation errors
[download]

I've read a lot about iterating on hashes and arrays, but I'm blocked by the complexity of the JSON. Why it tells me about %oneservice if I declared it as $oneservice?

Comment on Iterate over complex JSON Select or Download Code

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Re: Iterate over complex JSON by LanX (Saint) on Nov 23, 2014 at 02:04 UTC
nested data structure work with references and you need to dereference them explicitely in Perl. please try (untested) `my $service = $config->{'services'}; foreach $oneservice (@$service){ print $oneservice->{'service'}; }` [download] see `perlref` for details about references and `perldsc` for nested data structures HTH! :) Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :)}	[reply] [d/l]
Re^2: Iterate over complex JSON by Northwood128 (Initiate) on Nov 24, 2014 at 19:20 UTC
I'll try this. Thanks!! :)	[reply]
Re: Iterate over complex JSON by Anonymous Monk on Nov 23, 2014 at 01:41 UTC
add `use diagnostics;` to get better error messages; you asked for the free help of strict and warnings but you're not Coping with Scoping yet, see these links and my I've read a lot about iterating on hashes and arrays, but I'm blocked by the complexity of the JSON. Why it tells me about %oneservice if I declared it as $oneservice? Because you skipped reading perlintro. Because `%foo` is accessed as `$foo{bar}` but $baz is accessed as `$baz->{bar}`. See also References quick reference	[reply] [d/l] [select]
Re^2: Iterate over complex JSON by Northwood128 (Initiate) on Nov 24, 2014 at 19:18 UTC
Thanks for the advice!	[reply]