Retrieving Data from the Registry

To retrieve data from the registry, an application typically enumerates the subkeys of a key until it finds a particular one and then retrieves data from the value or values associated with it. An application can call either the RegEnumKey or RegEnumKeyEx function to enumerate the subkeys of a given key. RegEnumKeyEx returns a subkey and its class, but RegEnumKey returns only the subkey, not the class.

To retrieve detailed data about a particular subkey, an application can call the RegQueryInfoKey function. The RegGetKeySecurity function retrieves a copy of the security descriptor protecting a key.

An application can use the RegEnumValue function to enumerate the values for a given key, and the RegQueryValue or RegQueryValueEx function to retrieve a particular value for a key. An application typically calls RegEnumValue to determine the value names and then RegQueryValueEx to retrieve the data for the names.

RegQueryValue and RegQueryValueEx differ in how they treat unexpanded references to environment variables. If an unnamed value contains an unexpanded environment variable (for example, %PATH%), RegQueryValue expands the variable into the storage buffer provided as one of its parameters. RegQueryValueEx, however, does not expand these references. (Applications can also use the ExpandEnvironmentStrings function to expand environment variables.)

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