Search duplicates in Hash of Hash - perl

Question

i cant resolv this in my mind, its too much to me, perhaps someone can help me:
#Hosts = ("srv1","db1","srv2","db3","srv3","db3","srv3","db4","srv3","db5");
my $count = #Hosts;
$count= $count / 2;
my %hash;
$i = 0;
$ii = 1;
$j = 0;
$jj = 0;
while ($jj < $count) {
$hash{$j}{$Hosts[$i]} = $Hosts[$ii];
$i = $i + 2;
$ii = $ii +2;
$j++;
$jj++
}
print Dumper(\%hash);
Output:
$VAR1 = {
'4' => {
'srv4' => 'db3'
},
'1' => {
'srv2' => 'db3'
},
'3' => {
'srv3' => 'db3'
},
'0' => {
'srv1' => 'db1'
},
'2' => {
'srv3' => 'db3'
}
'5' => {
'srv3' => 'db5'
}
};
I Know this i ugly code, i dont know how to do that better, what i need to do is find douple servers and douple dbs, and put the positions and the string of the duplicates in an array ore something like that, i want to generate a Nagvis Map file out of that.
The Icinga Config file contains am Member string like this:
members srv1, db1, srv2, db3, srv3, db3, srv3, db3, srv4
It has pairs server, db, server, db, here is a sample of the Nagvis Config:
define host {
object_id=5e78fb
host_name=srv1
x=237
y=122
}
define service {
object_id=30646e
host_name=srv1
service_description=db1
x=52
y=122
}
define host {
object_id=021861
host_name=srv2
x=237
y=217
}
define service {
object_id=a5e725
host_name=srv1
service_description=db2
x=52
y=217
}
Thanks in advance

Answer 1

You need to clarify exactly what you want. It's very difficult to tell by your description.
And, your code is in very poor condition. Indenting loops and if statements like this:
while ($jj < $anzahl) {
$hash{$j}{$Hosts[$i]} = $Hosts[$ii];
$i = $i + 2;
$ii = $ii +2;
$j++;
$jj++
}
Makes your code much easier to understand. You also use generic names. What data is stored in #array? Is it a list of systems. Call it #systems. What is $i and $jj suppose to represent? What do you want $hash{$j}{$Hosts[$i]} to represent?
You should always, always, always add the following lines to the top of your program:
use strict;
use warnings;
If you use strict, you must declare all of your variables with my. This makes sure you don't do things like have #array in one place and #Hosts in another. These two lines will catch about 90% of your errors.
I don't know if you want a list of all the DB system that connect to the various servers or if you want a list of the various servers that connect to the DB systems. Therefore, I'll give you both.
I am guessing that your #array is a list of all of your machines and databases in one list:
use strict;
use warnings;
use feature qw(say); # Allows me to use "say" instead of "print"
use Data::Dumper;
my #systems = qw( # The qw(...) is like putting quotes around each word.
svr1 db1 # A nice way to define an array...
srv2 db3
srv3 db3
srv3 db4
srv3 db5
);
my %db_systems; # Database systems with their servers.
my %servers; # Servers with their database systems.
for (;;) { # Loop forever (until I say otherwise)
my $server = shift #systems;
#
# Let's check to make sure that there's a DB machine for this server
#
if ( not #systems ) {
die qq(Cannot get database for server "$server". Odd number of items in array);
}
my $database = shift #systems;
$servers{$server}->{$database} = 1;
$db_systems{$database}->{$server} = 1;
last if not #systems; # break out of loop if there are no more systems
}
say "Servers:" . Dumper \%servers;
say "Databases: " . Dumper \%db_systems;
This produces:
Servers:$VAR1 = {
'srv3' => {
'db4' => 1,
'db3' => 1,
'db5' => 1
},
'svr1' => {
'db1' => 1
},
'srv2' => {
'db3' => 1
}
};
Databases: $VAR1 = {
'db4' => {
'srv3' => 1
},
'db3' => {
'srv3' => 1,
'srv2' => 1
},
'db5' => {
'srv3' => 1
},
'db1' => {
'svr1' => 1
}
};
Is this close to what you want?
Addendum
Hi this is working!! Now i need to understand how to access the Values to print them in my file. This hash of hash thing is kind off ruff to mee. Thanks for that quick Help!
You need to read the Perl tutorial on References and the Perl Reference Page on References.
In Perl, all data is scalar which means that variables talk about single values. In other programming languages, you have structures or records, but not Perl.
Even arrays and hashes are nothing but collections of individual bits of data. What happens when you need something a bit more complex?
A reference is a memory location of another Perl data structure. You could have references to scalar variables like $foo, but that wouldn't do you much good in most circumstances. Where this is helpful is when you have a reference pointing to an array or a hash. This way, you could have much more complex structures that can be used to represent this data.
Imagine an array of ten items ($foo[0] to $foo[9]). Each entry in the array is pointing to another array of ten items. There are now 101 separate arrays being referenced here. We can treat them as a single structure, but it's important to remember that they are separate arrays.
I have a reference to an array at $foo[0]. How do I get access to the array itself? I do what is known as a dereference. To do that, I use curly braces with the right sigil in front. (The sigil is the $, #, or % you see in front of Perl variables:
$foo[0]; # Reference to an array
my #temp = #{ $foo[0] }; # Dereferencing.
my $temp[0]; # Now I can access that inner array
Having to use a temporary array each time I have to dereference it is rather clumsy, so I don't have to:
$foo[0]; # Reference to an array
my $value = ${ $foo[0] }[0]; # Getting the value of an item in my array reference
You can see that last is a bit hard to read. Imagine if I have a hash of a hash of an array of items:
my $phone = ${ ${ ${ $employee{$emp_number} }{phone} }[0] }{NUMBER};
It's a bit unwieldy. Fortunately, Perl allows you a few shortcuts. First, I can nest the references and use the default precedence:
my $phone = $employee{$emp_number}{phone}[0]{NUMBER};
I prefer using the -> notation:
my $phone = $employee{$emp_number}->{phone}->[0]->{NUMBER};
The arrow notion is cleaner because it separates the parts out, and it reminds you these are references!. and, not some complex structure data structure. This helps remind you when you have to do a dereference such as when you use the key, pop, or push commands:
for my $field ( keys %{ $employee } ) { # Dereference the hash
say "Field $field = " . $employee{$emp_number}->{$field}
if ( not ref $employee{$emp_number}->{$field} );
}
Look up the ref to see what it does and why I am only interested in printing out the field if ref returns an empty string.
By now, you should be able to see how to access your hash of hashes using the -> syntax:
my $db_for_server = $servers{$server}->{$database};
And you can use two loops:
for my $server ( keys %servers } {
my %db_systems = %{ $servers{$server} }; # Dereferencing
for my $db_system ( keys %db_systems } {
say "Server $server has a connection to $db_systems{$db_system}";
}
}
Or, without an intermediate hash...
for my $server { keys %servers } {
for my $db_system ( keys %{ $servers{$server} } ) {
say "Server $server has a connection to " . $servers{$server}->{$db_system};
}
}
Now, go out there and get a good book on Modern Perl. You need to learn good programming techniques like using good variable names, indenting, and using strict and warnings in order to help you write better programs that are easier to decipher and support.