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How to read and write registry keys in VC

Posted on 2003-03-17
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Last Modified: 2012-06-27
How can I read, write and make registrykeys?
Please make an example.
Thanks! :)
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Question by:TMM
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6 Comments
 
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Expert Comment

by:gj62
ID: 8154821
Sure - here's a link with complete source code for a Registry class that will do everything you need...

http://www.codeguru.com/system/registry_ult.shtml

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Expert Comment

by:jadams117
ID: 8155574
If using MS VC++ / MFC use SetRegistryKey() and GetProfileString(), WriteProfileString, GetProfileInt() and WriteProfileInt() from your CWinApp object
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Accepted Solution

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errorx666 earned 80 total points
ID: 8156686
   The registry is composed of keys and values organized in an hierarchical structure.  To referencing a key is very like referencing a file, you need to open it with the proper permissions and obtain a handle to that key (an HKEY).  The root of the registry is always a predefined key, these are constant but vary from different versions of Windows.  The current set of predefined keys as given by Microsoft is:
HKEY_CLASSES_ROOT
HKEY_CURRENT_CONFIG // Win95 / Win98 / WinME / WinNT4.0+
HKEY_CURRENT_USER
HKEY_DYN_DATA // Win95 / Win98 / WinME
HKEY_LOCAL_MACHINE
HKEY_PERFORMANCE_DATA // WinXP
HKEY_PERFORMANCE_NLSTEXT // WinXP
HKEY_PERFORMANCE_TEXT // WinXP
HKEY_USERS

    These predefined keys are declared in the standard Windows include, and can be used without explicitly opening them (with some restrictions).  To identify a key you need to give the handle (HKEY) of one of its parent members and a string specifying the relative path from that key and the key name (ie {HKEY_LOCAL_MACHINE."Software/MyCompany/MyProgram/Registration"}, or {hMyKey,"Registration"} ).  After you have successfully opened the key, you can use the handle in a number of functions to enumerate and modify either its subkeys or its values.

// Functions for opening and closing keys

LONG RegOpenKey(HKEY hKey, LPCTSTR lpSubKey, PHKEY phkResult);

LONG RegOpenKeyEx(HKEY hKey,LPCTSTR lpSubKey,DWORD ulOptions,REGSAM samDesired,PHKEY phkResult);

LONG RegCloseKey(HKEY hKey);

// Functions for creating and deleting keys

LONG RegCreateKey(HKEY hKey,LPCTSTR lpSubKey,PHKEY phkResult);

LONG RegCreateKeyEx(HKEY hKey,LPCTSTR lpSubKey,DWORD Reserved,LPTSTR lpClass,DWORD dwOptions,REGSAM samDesired,LPSECURITY_ATTRIBUTES lpSecurityAttributes,PHKEY phkResult,LPDWORD lpdwDisposition);

LONG RegDeleteKey(HKEY hKey,LPCTSTR lpSubKey);

// Functions for enumerating and querying keys

LONG RegEnumKey(HKEY hKey,DWORD dwIndex,LPTSTR lpName,DWORD cchName);

LONG RegEnumKeyEx(HKEY hKey,DWORD dwIndex,LPTSTR lpName,LPDWORD lpcName,LPDWORD lpReserved,LPTSTR lpClass,LPDWORD lpcClass,PFILETIME lpftLastWriteTime);

LONG RegQueryInfoKey(HKEY hKey,LPTSTR lpClass,LPDWORD lpcClass,LPDWORD lpReserved,LPDWORD lpcSubKeys,LPDWORD lpcMaxSubKeyLen,LPDWORD lpcMaxClassLen,LPDWORD lpcValues,LPDWORD lpcMaxValueNameLen,LPDWORD lpcMaxValueLen,LPDWORD lpcbSecurityDescriptor,PFILETIME lpftLastWriteTime);

    Values are the data associated with keys, they have names to identify them (or NULL for the default value of a key) and can be one of several flavors: REG_SZ (a NULL-terminated string, REG_DWORD (an unsigned long value), REG_BINARY (raw binary data [LPVOID]), REG_EXPAND_SZ (a NULL-terminated string containing environmental variables [use ExpandEnvironmentStrings]), REG_MULTI_SZ (an array of NULL-terminated strings).

// Functions to create or modify registry values

LONG RegSetValue(HKEY hKey,LPCTSTR lpSubKey,DWORD dwType,LPCTSTR lpData,DWORD cbData);

LONG RegSetValueEx(HKEY hKey,LPCTSTR lpValueName,DWORD Reserved,DWORD dwType,CONST BYTE *lpData,DWORD cbData);

// Function to delete registry values

LONG RegDeleteValue(HKEY hKey,LPCTSTR lpValueName);

// Functions to query and enumerate registry values

LONG RegQueryValue(HKEY hKey,LPCTSTR lpSubKey,LPTSTR lpValue,PLONG lpcbValue);

LONG RegQueryValueEx(HKEY hKey,LPCTSTR lpValueName,LPDWORD lpReserved,LPDWORD lpType,LPBYTE lpData,LPDWORD lpcbData);

LONG RegEnumValue(HKEY hKey,DWORD dwIndex,LPTSTR lpValueName,LPDWORD lpcValueName,LPDWORD lpReserved,LPDWORD lpType,LPBYTE lpData,LPDWORD lpcbData);

    You'll note that many of these functions take an excessive number of arguments, however most of these are optional (usually NULL can be given for pointers).  Here a simple program to create a registry key, write a value to it, then read that value back.

#include <windows.h>

int APIENTRY WinMain(HINSTANCE,HINSTANCE,LPSTR,int)
{
    HKEY hMyKey;
    DWORD BufferLength=10;
    char MyString[10];
    strcpy(MyString,"My string") // Set MyString
    RegCreateKey(HKEY_CURRENT_USER,"MyKey",hMyKey); // Create/open MyKey
    RegSetValueEx(hMyKey,"MyValue",REG_SZ,MyString,strlen(MyString)+1); // Store MyString
    ZeroMemory(MyString,10); // Clear MyString
    RegQueryValueEx(hMyKey,"MyValue",NULL,NULL,MyString,&BufferLength); // Load MyString
    RegCloseKey(hMyKey); // Close MyKey
    return 0;
};

     There are many more registry functions, this is a very deep topic.  I've tried to provide a brief overview of basic registry functionality.
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Expert Comment

by:errorx666
ID: 8156699
   Some slight errors in the code given.  Fixed here:

#include <windows.h>

int APIENTRY WinMain(HINSTANCE,HINSTANCE,LPSTR,int)
{
   HKEY hMyKey;
   DWORD BufferLength=10;
   char MyString[10];
   strcpy(MyString,"My string"); // Set MyString
   RegCreateKey(HKEY_CURRENT_USER,"MyKey",&hMyKey); // Create/open MyKey
   RegSetValueEx(hMyKey,"MyValue",NULL,REG_SZ,(LPBYTE)MyString,strlen(MyString)+1); // Store MyString
   ZeroMemory(MyString,10); // Clear MyString
   RegQueryValueEx(hMyKey,"MyValue",NULL,NULL,(LPBYTE)MyString,&BufferLength); // Load MyString
   RegCloseKey(hMyKey); // Close MyKey
   return 0;
};
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Author Comment

by:TMM
ID: 8168016
Thanks! It was very helpful;)!
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