How can I set PATH variable using QT?

Question

How can I get and set PATH variable using QT 4.8? I know I can get PATH variable values using getenv from the STL but don't know how to set it using STL or any Qt based method?

If QT has a function for it, I would like to know and use it rather than going and using Windows API for it.

Answer 1

Thanks to my friend Mr. Toosi, you can set environment variable for current process using qputenv("key", "value") and get it using qgetenv("key").
This works on Qt 5.5.0 too :)

Answer 2

You can use setenv from stdlib.h to set PATH to a new value.

setenv("PATH","/new/path/value",1)

However, this is a non-standard extension to the standard headers, and will only affect sub-processes spawned by the calling process. In order to change environment variables for all new processes spawned, a system-specific method must be used. For windows, the PATH variable can be changed in the

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment

registry key. This will make sure the PATH is set for all new processes, and will apply over a reboot.

Answer 3

I worked with the Registry value using this code:

Include:

#include <windows.h>

To read:

QSettings setting( "HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Control\\Session Manager\\Environment", QSettings::NativeFormat );
QString pathVal = setting.value("Path", "no-path").toString();

To write:

setting.setValue( "Path", path );
SendMessageA( HWND_BROADCAST, WM_SETTINGCHANGE, 0, (LPARAM)"Environment" );

This way I get the actual Path value without reloading the program and write the value broadcasting the change to all processes.

Couldn't realize first how to use SendMessage from this answer:
How to modify the PATH variable definitely through the command line in Windows.
I thought I should create a Win32 app in Visual Studio and then send this message inside of it.

But this function should be called just after the registry changed. So I could edit the registry value manually and then press a button which called the SendMessageA and the Path updated.

---

BTW, there is SendMessage macro which calls SenMessageW function but it didn't work and the Path didn't change. Don't know what the A means but it changes the variable.