check windows registry key existence

[mentalmushroom]

Hi there! I'd like to know whether it is possible to find out if a registry key exists by the means of QSettings. I was trying to use QSettings::contains, but it doesn't work.

QSettings reg("HKEY_LOCAL_MACHINE\\Software\\VideoLan", QSettings::NativeFormat);	
bool exists = reg.contains("VLC");

QSettings reg("HKEY_LOCAL_MACHINE\\Software\\VideoLan", QSettings::NativeFormat);	
bool exists = reg.contains("VLC");

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[JohannesMunk]

Could it be that "VLC" is a subkey and not a value? Does this work?

QSettings reg("HKEY_LOCAL_MACHINE\\Software\\VideoLan\\VLC", QSettings::NativeFormat);    
bool exists = reg.contains("Default");

QSettings reg("HKEY_LOCAL_MACHINE\\Software\\VideoLan\\VLC", QSettings::NativeFormat);    
bool exists = reg.contains("Default");

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Joh

[mentalmushroom]

Yes, VLC is a subkey and not a value. But I thought QSettings::contains is intended to be used for keys. Your code works, but I can't check key the way you said, because actually I don't need registry keys to be created (QSettings will create key if "HKEY_LOCAL_MACHINE\\Software\\VideoLan\\VLC" doesn't exist), therefore I need to use somethings like:

QSettings reg("HKEY_LOCAL_MACHINE", QSettings::NativeFormat);	
bool exists = reg.contains("Software\\VideoLan\\VLC");

QSettings reg("HKEY_LOCAL_MACHINE", QSettings::NativeFormat);	
bool exists = reg.contains("Software\\VideoLan\\VLC");

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or

QSettings reg("HKEY_LOCAL_MACHINE", QSettings::NativeFormat);	
bool exists = reg.contains("Software\\VideoLan\\VLC\\Default");

QSettings reg("HKEY_LOCAL_MACHINE", QSettings::NativeFormat);	
bool exists = reg.contains("Software\\VideoLan\\VLC\\Default");

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Or I don't know how to do it in a better way. But anyway this doesn't work.

[JohannesMunk]

Well no idea. As this is highly platform dependent anyway, why don't you use winapi directly?

#ifdef Q_OS_WIN
#include "windows.h"
#endif
 
    bool existsAndSuccess = false;
#ifdef Q_OS_WIN
    HKEY hKey;
    existsAndSuccess  = (RegOpenKeyExW(HKEY_LOCAL_MACHINE, L"Software\\VideoLan\\VLC", 0, KEY_READ, &hKey) == ERROR_SUCCESS);
#endif
    qDebug() << existsAndSuccess;

#ifdef Q_OS_WIN
#include "windows.h"
#endif

    bool existsAndSuccess = false;
#ifdef Q_OS_WIN
    HKEY hKey;
    existsAndSuccess  = (RegOpenKeyExW(HKEY_LOCAL_MACHINE, L"Software\\VideoLan\\VLC", 0, KEY_READ, &hKey) == ERROR_SUCCESS);
#endif
    qDebug() << existsAndSuccess;

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Maybe somebody else knows how to do this with QSettings properly?

Joh

[mentalmushroom]

yes, i ended up with this approach. but later i use qsettings anyway (because it is easier), therefore i thought to use qsettings for this check also and, generally, i was interested whether it is possible. ok, thank you.