RegQueryValueEx
A version of this page is also available for
4/8/2010
This function retrieves the type and data for a specified value associated with an open registry key.
A remote application interface (RAPI) version of this function exists called CeRegQueryValueEx (RAPI).
Syntax
LONG RegQueryValueEx(
HKEY hKey,
LPCWSTR lpValueName,
LPDWORD lpReserved,
LPDWORD lpType,
LPBYTE lpData,
LPDWORD lpcbData
);
Parameters
hKey
[in] Handle to a currently open key or any of the following predefined reserved handle values:HKEY_LOCAL_MACHINE
HKEY_CLASSES_ROOT
HKEY_CURRENT_USER
HKEY_USERS
- lpValueName
[in] Pointer to a string containing the name of the value to query. If this parameter is set to NULL or an empty string, the value queried is the value named "Default".
- lpReserved
[in] Reserved. Set to NULL.
lpType
[out] Pointer to a variable that receives the type of data associated with the specified value. The following table shows possible values.Value Description REG_BINARY
Specifies binary data in any form.
REG_DWORD
Specifies a 32-bit number.
REG_DWORD_BIG_ENDIAN
Specifies a 32-bit number in big-endian format.
In big-endian format, a multibyte value is stored in memory from the highest byte to the lowest byte. For example, the value 0x12345678 is stored as
(0x12 0x34 0x56 0x78)in big-endian format.REG_DWORD_LITTLE_ENDIAN
Specifies a 32-bit number in little-endian format. This is equivalent to REG_DWORD.
In little-endian format, a multibyte value is stored in memory from the lowest byte to the highest byte. For example, the value 0x12345678 is stored as
(0x78 0x56 0x34 0x12)in little-endian format.REG_EXPAND_SZ
Specifies a null-terminated string that contains unexpanded references to environment variables. For example,
%PATH%.REG_LINK
Specifies a Unicode symbolic link. Used internally. Applications do not use this type.
REG_MULTI_SZ
Specifies an array of null-terminated strings, terminated by two null characters.
REG_NONE
No defined value type.
REG_RESOURCE_LIST
Specifies a device-driver resource list.
REG_SZ
Specifies a null-terminated Unicode string.
This parameter can be set to NULL if the type is not required.
- lpData
[out] Pointer to a buffer that receives value data. This parameter can be set to NULL if the data is not required.
lpcbData
[in, out] Pointer to a variable that specifies the size, in bytes, of the buffer pointed to by the lpData parameter. When the function returns, this variable contains the size of the data copied to lpData.If the data has the REG_SZ, REG_MULTI_SZ or the REG_EXPAND_SZ type, this function checks for a terminating null character. If one is not found, the string is stored with a null terminator. This parameter also includes the size of the terminating null character.
This parameter can be set to NULL only if lpData is set to NULL.
If the buffer specified by lpData is not large enough to hold the data, including a null terminator for string data, the function returns ERROR_MORE_DATA and stores the required buffer size, in bytes, to the variable pointed to by this parameter.
If lpData is set to NULL, and this parameter is non-NULL, the function returns ERROR_SUCCESS and stores the size of the data, in bytes, in the variable pointed to by this parameter. This enables an application to determine the best way to allocate a buffer for value data.
Return Value
ERROR_SUCCESS indicates success. A nonzero error code defined in Winerror.h indicates failure. To get a generic description of the error, call the FormatMessage function with the FORMAT_MESSAGE_FROM_SYSTEM flag set. The message resource is optional, so FormatMessage might fail.
Requirements
| Header | winreg.h |
| Library | coredll.lib |
| Windows Embedded CE | Windows CE 1.0 and later |
| Windows Mobile | Windows Mobile Version 5.0 and later |
See Also
Reference
Registry Functions
RegCreateKeyEx
RegEnumKeyEx
RegEnumValue
RegOpenKeyEx
RegQueryInfoKey