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22.15. Win32::Registry

This module provides access to the
Windows Registry, the database that stores information about all
parts of your system and software. Many operating-system and
application behaviors are controlled by Registry data. The
Win32::Registry module gives you a way to access and update registry
information with Perl.

WARNING:
Always be careful when making changes to the registry. If vital
system information gets changed by mistake, your system could become
inoperable. Always make certain you have a backup of your registry
before you start making modifications.

The Registry module
automatically creates objects for the top-level registry trees. These
objects are created in the main:: namespace, and
each key that you open or create is accessed via one of these root
objects. The top-level objects are:

$HKEY_CLASSES_ROOT
$HKEY_CURRENT_USER
$HKEY_LOCAL_MACHINE
$HKEY_USERS
$HKEY_PERFORMANCE_DATA
$HKEY_CURRENT_CONFIG
$HKEY_DYN_DATA

If you are outside of the main (default) namespace, you should
package declare the keys, e.g., $main::HKEY_USERS.

The Open
method creates new key objects for subtrees or subkeys under another
open key object. Initially, a new key is opened from one of the main
key objects. For example:

use Win32::Registry;
$p = "SOFTWARE\Microsoft\Windows NT\CurrentVersion";
$HKEY_LOCAL_MACHINE->Open($p, $CurrVer) || die "Open $!";

This example creates a key object $CurrVer for the
CurrentVersion key for Windows NT. This key
contains several values for the current version of the operating
system. With the new key open, you can read or change the values it
contains (every key has at least one unnamed, default value), or open
and create subkeys. The Open method can create key
objects only for existing keys.

Registry values are represented in Win32::Registry functions by three
elements: the name of the value, the data type of the value, and the
value itself. There are several different data types for the values.
Win32::Registry defines the following constants for these types:

REG_SZ

String data

REG_DWORD

Unsigned four-byte integer

REG_MULTI_SZ

Multiple strings delimited with NULL

REG_EXPAND_SZ

Strings that expand (e.g., based on environment variables)

REG_BINARY

Binary data (no particular format is assumed)

22.15.1. Win32::Registry Methods

The following methods can be used on key objects, either on the
preopened main keys or subkeys that you have already opened.

$key->Create($newkey, name)

Creates a new key identified by
name and saves it as the object reference
named by $newkey. If
the key already exists, this function simply opens the key. New keys
can only be created one level below the key on which
Create is used.

$key->DeleteKey(subkey)

Deletes a subkey of the
current key. This function will delete all values in the subkey and
the subkey itself. A key cannot be deleted if it contains any
subkeys.

$key->DeleteValue(name)

Deletes a value identified
by name from the current key.

$key->GetKeys($listref)

Returns the names of the
subkeys of the current key to the list referenced by
listref.

$key->GetValues($hashref)

Returns the values contained
in the current key to the hash referenced by
hashref. Each registry value name is a
hash key, while the hash value is a reference to a three-element list
containing the name of the value, the data type, and the value.

$key->Load(subkey, filename)

Loads a registry file to the named
subkey from file
filename.

$parent->Open(keyname, $key)

Opens a registry key named in keyname and
saves it as the object reference named by
$key.
keyname is the name of a key relative to
the object on which Open is used
($parent).

$key->QueryKey($class, $subs, $vals)

Retrieves information about
the current key and returns it to the named scalar variables. The key
class is saved in the class variable (it
will be the null string " on Win95
since it doesn''t use key classes). The number of
subkeys is saved in the
$subs variable, and the
number of values in the current key is saved in
$vals.

$key->QueryValue(name, $var)

Returns the value of the
registry value specified by name and saves
it in the scalar variable
$var.

$key->Save(filename)

Saves the registry tree root and the
current key to a file, filename.

$key->SetValue(subkey, type, value)

Sets the default (unnamed)
value for the specified subkey of the key object on which
SetValue is used. The arguments are:

subkey

Name of the subkey

type

One of the type constants (listed above) describing the value

value

Value of the key

$key->SetValueEx(name, res, type, value)

Sets a value specified by
name in the current key (or creates the
value if it doesn''t already exist). The arguments
are:

res

A reserved argument for future use (use 0 as a
placeholder)

type

The data type constant (listed above) describing the value

value

The value of the key