I managed to create a hash data set with a subroutine,
my %check_ip = (
"data1" => $ip1,
"data2" => $ip2,
"data3" => $ip3
);
'data1' => '127.0.0.1',
'data2' => '192.168.0.1',
'data3' => '192.168.1.1'
This is a simple hash.
I am looking to put another key behind this, so that this would become a hash of hash, and look like
config1 =>
'data1' => '127.0.0.1',
'data2' => '192.168.0.1',
'data3' => '192.168.1.1',
What is the best way to do this?
To create a nested hash, you need a hash reference.
my %check_ip = (
data1 => $ip1,
data2 => $ip2,
data3 => $ip3,
);
my %config = ( config1 => \%check_ip );
#!/usr/bin/perl
use strict;
use warnings;
my $ip1='127.0.0.1';
my $ip2='192.168.0.1';
my $ip3='192.168.1.1';
my %check_ip = (
config1 => { "data1" => $ip1,
"data2" => $ip2,
"data3" => $ip3, },
);
Access like below:
print $check_ip{config1}{data1}; #output 127.0.0.1
Demo
Since a hash key can only have one value, the nested hash needs to be stored as a hash reference, which is what the curly braces {} are used for:
my %check_ip = (
config1 => { "data1" => $ip1,
"data2" => $ip2,
"data3" => $ip3, },
);
See perldoc perldsc for more information on Perl data structures.
Related
I am loading a config file, which ends up as an embedded hash, with Config::IniFiles. After that, I want to modify the resulting hash by, for some keys, bringing its values one level up. In the example below, I am aiming for this as a result:
$VAR1 = {
'max_childrensubtree' => '7',
'port' => '1984',
'user' => 'someuser',
'password' => 'somepw',
'max_width' => '20',
'host' => 'localhost',
'attrs' => {
'subattr2' => 'cat',
'topattr1' => 'cat',
'subattr2_1' => 'pt',
'subattr1' => 'rel'
},
'max_descendants' => '1000'
};
So for the keys params and basex at the highest level, I want to move its contents (key-value pairs) to the highest level - and remove the items themselves. In short:
(
a => {
'key1' => 'ok',
'key2' => 'hello'
}
)
turns into
(
'key1' => 'ok',
'key2' => 'hello'
)
The strange thing is that what I am trying to do does not work on a hash built from a read INI file, but it does work with a manually inserted hash. In other words, this works:
#!/usr/bin/perl
use utf8;
use strict;
use warnings;
use Data::Dumper;
my %ini = (
'params' => {
'max_width' => '20',
'max_childrensubtree' => '7',
'max_descendants' => '1000'
},
'attrs' => {
'topattr1' => 'cat',
'subattr1' => 'rel',
'subattr2' => 'cat',
'subattr2_1' => 'pt',
},
'basex' => {
'host' => 'localhost',
'port' => '1984',
'user' => 'someuser',
'password' => 'somepw'
}
);
&_parse_ini(\%ini);
sub _parse_ini {
my $ref = shift;
foreach (('params', 'basex')) {
foreach my $k (keys %{$ref->{$_}}) {
$ref->{$k} = $ref->{$_}->{$k};
}
delete $ref->{$_};
}
print Dumper($ref);
}
But this does not:
#!/usr/bin/perl
use utf8;
use strict;
use warnings;
use Data::Dumper;
use Config::IniFiles;
# Load config file
tie my %ini, 'Config::IniFiles', (-file => $ARGV[0]);
&_parse_ini(\%ini);
sub _parse_ini {
my $ref = shift;
foreach (('params', 'basex')) {
foreach my $k (keys %{$ref->{$_}}) {
$ref->{$k} = $ref->{$_}->{$k};
}
delete $ref->{$_};
}
print Dumper($ref);
}
The input ini file for this example would be:
[params]
max_width = 20
max_childrensubtree = 7
max_descendants = 1000
[attrs]
topattr1 = cat
subattr1 = rel
subattr2 = cat
subattr2_1 = pt
[basex]
host = localhost
port = 1984
user = admin
password = admin
I have been looking in the documentation and on SO for similar issues but have found none. It appears that the hashes are identical (Config::IniFiles doesn't seem to add something specific), so I have no idea why it works for 'manual' hashes, and not for read-in ones.
The two hashes are not identical at all, although they may appear to be from the point of view of the data they contain.
The first one is a regular hash. You can do whatever you like with it.
The second one is a tied hash. It becomes an object of Config::IniFiles, but with a hash like interface. So whilst it appears to be a hash, the package can override the methods for storing or fetching information in the hash however it likes.
In this particular case, it looks like Config::IniFiles will only store a new key value in the hash if the value is hash ref. So you can't flatten out the tied hash as you want. Instead you'll have to create a new hash and copy the data in to it to do what you want.
I've tried many different versions of using push and splice, but can't seem to combine two hashes as needed. Trying to insert the second hash into the first inside the 'Item' array:
(
ItemData => { Item => { ItemNum => 2, PriceList => "25.00", UOM => " " } },
)
(
Alternate => {
Description => "OIL FILTER",
InFile => "Y",
MfgCode => "FRA",
QtyAvailable => 29,
Stocked => "Y",
},
)
And I need to insert the second 'Alternate' hash into the 'Item' array of the first hash for this result:
(
ItemData => {
Item => {
Alternate => {
Description => "OIL FILTER",
InFile => "Y",
MfgCode => "FRA",
QtyAvailable => 29,
Stocked => "Y",
},
ItemNum => 2,
PriceList => "25.00",
UOM => " ",
},
},
)
Can someone suggest how I can accomplish this?
Assuming you have two hash references, this is straight-forward.
my $item = {
'ItemData' => {
'Item' => {
'PriceList' => '25.00',
'UOM' => ' ',
'ItemNum' => '2'
}
}
};
my $alt = {
'Alternate' => {
'MfgCode' => 'FRA',
'Description' => 'OIL FILTER',
'Stocked' => 'Y',
'InFile' => 'Y',
'QtyAvailable' => '29'
}
};
$item->{ItemData}->{Item}->{Alternate} = $alt->{Alternate};
The trick here is not to actually merge $alt into some part of $item, but to only take the specific part you want and put it where you want it. We take the Alternate key from $alt and put it's content into a new Alternate key inside the guts of $item.
Adam Millerchip pointed out in a hence deleted comment that this is not a copy. If you alter any of the keys inside of $alt->{Alternative} after sticking it into $item, the data will be changed inside of $item as well because we are dealing with references.
$item->{ItemData}->{Item}->{Alternate} = $alt->{Alternate};
$alt->{Alternate}->{InFile} = 'foobar';
This will actually also change the value of $item->{ItemData}->{Item}->{Alternate}->{InFile} to foobar as seen below.
$VAR1 = {
'ItemData' => {
'Item' => {
'ItemNum' => '2',
'Alternate' => {
'Stocked' => 'Y',
'MfgCode' => 'FRA',
'InFile' => 'foobar',
'Description' => 'OIL FILTER',
'QtyAvailable' => '29'
},
'UOM' => ' ',
'PriceList' => '25.00'
}
}
};
References are supposed to do that, because they only reference something. That's what's good about them.
To make a real copy, you need to dereference and create a new anonymous hash reference.
# create a new ref
# deref
$item->{ItemData}->{Item}->{Alternate} = { %{ $alt->{Alternate} } };
This will create a shallow copy. The values directly inside of the Alternate key will be copies, but if they contain references, those will not be copied, but referenced.
If you do want to merge larger data structures where more than the content of one key needs to be merged, take a look at Hash::Merge instead.
I am always confusing or don't know how to handle hash in perl.
So here is the problem,
Considering the whole thing, i am trying to change the key name in the below hash.
my %hash_new = {
'customername' => 'Lee & toys',
'employee_name' => 'Checngwang',
'customer_id' => 'X82349K',
'customer_address' => 'classic denver ranch, meadows drive',
'types' => 'category la',
};
my %selectCols = ('customername' => 'CUSTOMERNAME','employee_name' => 'EMP_NAME','customer_id' => 'cusid','customer_address' => 'cusaddr','types' => 'Typs');
my %new_hash = ();
foreach my $hash_keys (keys %hash_new){
my $newKey = $selectCols{$hash_keys};
$new_hash{$newKey} = $hash_new{$hash_keys};
}
print Dumper %new_hash;
Output of %new_hash is something like a key value combination of continuous string as below,
CUTOMERNAMELee & toysEMP_NAMEChecngwangcus_idX82349Kcusaddrclassic denver ranch, meadows driveTypscategory la
But instead of this, i need the hash like,
$VAR1 = {
'CUSTOMERNAME' => 'Lee & toys',
'EMP_NAME' => 'Checngwang',
'cusid' => 'X82349K',
'cusaddr' => 'classic denver ranch, meadows drive',
'Typs' => 'category la',
};
Please help me around this!
If I understood you correctly, then this works:
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my %hash_new = (
'customername' => 'Lee & toys',
'employee_name' => 'Checngwang',
'customer_id' => 'X82349K',
'customer_address' => 'classic denver ranch, meadows drive',
'types' => 'category la'
);
my %selectCols = (
'customername' => 'CUSTOMERNAME',
'employee_name' => 'EMP_NAME',
'customer_id' => 'cusid',
'customer_address' => 'cusaddr',
'types' => 'Typs'
);
my %new_hash = ();
foreach my $hash_keys (keys %hash_new){
my $newKey = $selectCols{$hash_keys};
$new_hash{$newKey} = $hash_new{$hash_keys};
}
print Dumper \%new_hash;
The only code I changed in your code was using () instead of {} in %hash_new and escaped the % in the Dumper statement. The % should be escaped because Dumper expects a reference, not a hash (that's true also for all other Perl variable types in use with Dumper).
Output:
$VAR1 = {
'Typs' => 'category la',
'cusaddr' => 'classic denver ranch, meadows drive',
'EMP_NAME' => 'Checngwang',
'cusid' => 'X82349K',
'CUSTOMERNAME' => 'Lee & toys'
};
Also, don't use confusing names like %hash_new and %new_hash. It's - well - confusing.
I'm using the PerlMonk example I found on:
Reading and Writing Perl Config Files
Configuration.pl:
%CFG = (
'servers' => {
'SRV1' => {
'IP' => 99.32.4.0,
'user' => 'aname',
'pswd' => 'p4ssw0rd',
'status' => 'unavailable'
},
'SRV2' => {
'IP' => 129.99.10.5
'user' => 'guest',
'pswd' => 'guest'
'status' => 'unavailable'
}
},
'timeout' => 60,
'log' => {
'file' => '/var/log/my_log.log',
'level' => 'warn',
},
'temp' => 'remove me'
);
It is working great, but the only issue is when reading and writing the HASH like configuration is being 'out of order'.
Is there a way to keep it TIED?
This important since the configuration file will be also edited manually, so I want the keys and values in the same order.
You could tie config variable before using it, so later hash keys will stay in same order as before,
use strict;
use warnings;
use Tie::IxHash;
tie my %CFG, 'Tie::IxHash';
%CFG = (
'servers' => {
'SRV1' => {
'IP' => '99.32.4.0',
'user' => 'aname',
'pswd' => 'p4ssw0rd',
'status' => 'unavailable'
},
'SRV2' => {
'IP' => '129.99.10.5',
'user' => 'guest',
'pswd' => 'guest',
'status' => 'unavailable'
}
},
'timeout' => 60,
'log' => {
'file' => '/var/log/my_log.log',
'level' => 'warn',
},
'temp' => 'remove me'
);
use Data::Dumper;
print Dumper \%CFG;
If you use JSON then you have the advantage that your software is safe from a malicious attack (or perhaps accidental corruption). JSON also has a simpler syntax than Perl data structures, and it is easier to recover from syntax errors.
Setting the canonical option will create the data with the keys in sorted order, and so generate the same output for the same Perl data every time. If you need the data in a specific order other than alphabetical then you can use the Tie::IxHash module as #mpapec describes in his answer.
Alternatively you can use the sort_by method from the Pure Perl version of the module that lets you pass a collation subroutine. That would let you prescribe the order of your keys, and could be as simple as using a hash that relates all the possible key values with a numerical sort order.
This program uses the sort_by method to reconstruct the JSON in the same order as the keys appear in your original hash. That is unlikely to be the order you want, but the mechanism is there. It works by looking up each key in a hash table to determine how they should be ordered. Any keys (like SVR1 and SVR2 here) that don't appear in the hash are sorted in alphabetical order by default.
use strict;
use warnings;
use JSON::PP ();
my %CFG = (
'servers' => {
'SRV1' => {
'IP' => '99.32.4.0',
'user' => 'aname',
'pswd' => 'p4ssw0rd',
'status' => 'unavailable'
},
'SRV2' => {
'IP' => '129.99.10.5',
'user' => 'guest',
'pswd' => 'guest',
'status' => 'unavailable'
}
},
'timeout' => 60,
'log' => {
'file' => '/var/log/my_log.log',
'level' => 'warn',
},
'temp' => 'remove me'
);
my %sort_order;
my $n = 0;
$sort_order{$_} = ++$n for qw/ servers timeout log temp /;
$sort_order{$_} = ++$n for qw/ IP user pswd status /;
$sort_order{$_} = ++$n for qw/ file level /;
my $json = JSON::PP->new->pretty->sort_by(\&json_sort);
print $json->encode(\%CFG);
sub json_sort {
my ($aa, $bb) = map $sort_order{$_}, $JSON::PP::a, $JSON::PP::b;
$aa and $bb and $aa <=> $bb or $JSON::PP::a cmp $JSON::PP::b;
}
generates this output
{
"servers" : {
"SRV1" : {
"IP" : "99.32.4.0",
"user" : "aname",
"pswd" : "p4ssw0rd",
"status" : "unavailable"
},
"SRV2" : {
"IP" : "129.99.10.5",
"user" : "guest",
"pswd" : "guest",
"status" : "unavailable"
}
},
"timeout" : 60,
"log" : {
"file" : "/var/log/my_log.log",
"level" : "warn"
},
"temp" : "remove me"
}
which can simply be saved to a file and similarly restored.
I dumped a data structure:
print Dumper($bobo->{'issues'});
and got:
$VAR1 = {
'155' => {
'name' => 'Gender',
'url_name' => 'gender'
}
};
How can I extract 155?
How about if I have:
$VAR1 = {
'155' => {'name' => 'Gender', 'url_name' => 'gender'},
'11' => {'name' => 'Toddler', 'url_name' => 'toddler'},
'30' => {'name' => 'Lolo', 'url_name' => 'lolo'}
};
I want to print one key, i.e. the first or second to see the value of the key?
So, based on the example you posted, the hash looks like this:
$bobo = {
issues => {
155 => {
name => 'Gender',
url_name => 'gender',
},
},
};
'155' is a key in your example code. To extract a key, you would use keys.
my #keys = keys %{$bobo->{issues}};
But to get the value that 155 indexes, you could say:
my $val = $bobo->{issues}{155};
Then $val would contain a hashref that looks like this:
{
name => 'Gender',
url_name => 'gender'
}
Have a look at perldoc perlreftut.
It is a key in the hash referenced by $bobo->{'issues'}. So you would iterate through
keys %{$bobo->{'issues'}}
to find it.