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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.

Open

$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).



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