RegQueryValueEx

This function retrieves the type and data for a specified value name associated with an open registry key.

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_CLASSES_ROOT
  • HKEY_CURRENT_USER
  • HKEY_LOCAL_MACHINE
  • HKEY_USERS

• lpValueName
  [in] Pointer to a string containing the name of the value to query. If this parameter is NULL or an empty string, the function retrieves the type and data for the keys unnamed value. A registry key does not automatically have an unnamed or default value. Unnamed values can be of any type.

• lpReserved
  [in] Reserved; set to NULL.

• lpType
  [out] Pointer to a variable that receives the type of data associated with the specified value. The value returned through this parameter will be one of the following:

  Value	Description
  REG_BINARY	Binary data in any form.
  REG_DWORD	A 32-bit number.
  REG_DWORD_LITTLE_ENDIAN	A 32-bit number in little-endian format. This is equivalent to REG_DWORD.
  	In little-endian format, a multi-byte value is stored in memory from the lowest byte (the little end) to the highest byte. For example, the value 0x12345678 is stored as (0x78 0x56 0x34 0x12) in little-endian format.
  REG_DWORD_BIG_ENDIAN	A 32-bit number in big-endian format.
  	In big-endian format, a multi-byte value is stored in memory from the highest byte (the big end) to the lowest byte. For example, the value 0x12345678 is stored as (0x12 0x34 0x56 0x78) in big-endian format.
  REG_EXPAND_SZ	A null-terminated string that contains unexpanded references to environment variables (for example, %PATH%).
  REG_LINK	A Unicode symbolic link. Used internally; applications should not use this type.
  REG_MULTI_SZ	An array of null-terminated strings, terminated by two null characters.
  REG_NONE	No defined value type.
  REG_RESOURCE_LIST	A device-driver resource list.
  REG_SZ	A null-terminated string.

  The lpType parameter can be NULL if the type is not required.

• lpData
  [out] Pointer to a buffer that receives the values data. This parameter can be 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 REG_EXPAND_SZ type, then lpcbData will also include the size of the terminating null character.

  The lpcbData parameter can be NULL only if lpData is NULL.

  If the buffer specified by lpData parameter is not large enough to hold the data, the function returns the value ERROR_MORE_DATA, and stores the required buffer size, in bytes, into the variable pointed to by lpcbData.

  If lpData is NULL, and lpcbData is non-NULL, the function returns ERROR_SUCCESS, and stores the size of the data, in bytes, in the variable pointed to by lpcbData. This lets an application determine the best way to allocate a buffer for the values data.

Return Values

ERROR_SUCCESS indicates success. A nonzero error code defined in Winerror.h indicates failure. To get a generic description of the error, call FormatMessage with the FORMAT_MESSAGE_FROM_SYSTEM flag set. The message resource is optional; therefore, if you call FormatMessage it could fail.

Remarks

The key identified by hKey must have been opened with KEY_QUERY_VALUE access. To open the key, use the RegCreateKeyEx or RegOpenKeyEx function.

Windows CE supports only the Unicode version of this function.

Requirements

Note   This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.

See Also

RegCreateKeyEx, RegEnumKeyEx, RegEnumValue, RegOpenKeyEx, RegQueryInfoKey

 Last updated on Tuesday, July 13, 2004

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