FreeKB - Perl (Scripting) Hash (lock_keys lock_values)
Perl (Scripting) - Hash (lock_keys lock_values)

In Perl, there are 3 different kinds of hashes.

  • A regular hash, which is defined by the % and ( ) characters - %hash = ( );
  • A reference hash, which is defined with the $ and { } characters = $hash = { };
  • A hash array, which is defined with the % and [ ] characters - %hash = [ ];

 

Let's say you have the following hash. In this example, the foo key in the hash is empty.

my %hash = ( 'foo' => '' );

 

A value can be appended to the employee key, like this.

$hash{foo} = "bar";

 

Dumper can be used to display the structure of the hash.

use Data::Dumper;
print Dumper \%hash;

 

Now, the employee key contains a value of John Doe.

$VAR1 = {
           'foo' => 'bar'
        };

 

The lock_keys and lock_value subroutines can be used to lock the key, so that the value in the key cannot be modified.

use Hash::Util qw (lock_keys unlock_keys lock_value unlock_value);

 

In this example, every key in the hash is locked, so that no keys can be added, modified, or removed. 

lock_keys (%hash);

 

The value with the employee key is locked, so that the value cannot be modified or removed.

lock_value(%hash, "foo");

 

Attempting to modify the value of a locked key value pair . . .

$hash{foo} = "Hello World";

 

. . . will produce the following.

Modification of a read-only value attempted

 

The value can be unlocked.

unlock_value(%hash, "foo");

 

Every key in the hash can be unlocked, so that keys can be added, modified, or removed. 

unlock_keys (%hash);


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