fcl-registry is an FCL unit that provides access to the Windows registry. It is cross-platform. How? In non-Windows operating systems it creates a reg.xml file. For example, under non-Windows operating systems it creates the per user XML file (HKEY_CURRENT_USER) reg.xml in the /home/[user]/.config/application_name/ directory; the global XML file (HKEY_LOCAL_MACHINE) reg.xml is created in the /etc/application_name/ directory which is invariably a read-only location unless you are the root or Admin user.
RootKey: registry hive where you want to start accessing the registry. Examples: HKEY_LOCAL_MACHINE, HKEY_CURRENT_USER
Key: the path to the "directory" that contains individual data. This is a bit counter-intuitive but a holdover from compatibility with earlier versions of the registry.
Name/value: the actual name/value pairs in the Key "directory". Each key can have a default value, whose name is (an empty string).
Example that tries to get a value:
uses ... registry... var CompileCommand: string=''; Registry: TRegistry; begin Registry := TRegistry.Create; try // Navigate to proper "directory": Registry.RootKey := HKEY_LOCAL_MACHINE; if Registry.OpenKeyReadOnly('\SOFTWARE\Classes\InnoSetupScriptFile\shell\Compile\Command') then CompileCommand:=Registry.ReadString(''); //read the value of the default name finally Registry.Free; // In non-Windows operating systems this flushes the reg.xml file to disk end; end;
Accessing 64 bit and 32 bit registry views
If you have 64 bit Windows, the registry is split up into a 64 bit and 32 bit (compatibility) part. By default, if you run a 32 bit process, you see the 32 bit part; if you run a 64 bit application, you see the 64 bit part.
You can also access the 32 bit part from 64 bit applications and vice versa. From MSDN
- KEY_WOW64_64KEY: Access a 64-bit key from either a 32-bit or 64-bit application.
- KEY_WOW64_32KEY: Access a 32-bit key from either a 32-bit or 64-bit application.
These keys are defined in the registry unit so you can just use them: eg in the registry object's Access property, like this:
Registry := TRegistry.Create; Try Registry.Access:=Registry.Access or KEY_WOW64_64KEY;
or in the registry.create call, eg:
TRegistry.Create(KEY_READ or KEY_WOW64_64KEY);
Depending on what you want to read/write in the Windows registry, you may need administrator rights and elevation (Windows Vista+). Please see Use manifest file to set execution level