HOWTO: Propagating Environment Variables to the System

 Last reviewed: May 27, 1997
Article ID: Q104011
The information in this article applies to:
  • Microsoft Win32 Application Programming Interface (API) included with: - Microsoft Windows NT versions 3.5, 3.51, 4.0

SUMMARY

User environment variables can be modified by editing the following Registry key: 

   HKEY_CURRENT_USER \
         Environment
System environment variables can be modified by editing the following Registry key: 

   HKEY_LOCAL_MACHINE \
               SYSTEM \
    CurrentControlSet \
              Control \
      Session Manager \
          Environment
Note, however, that modifications to the environment variables do not result in immediate change. For example, if you start another Command Prompt after making the changes, the environment variables will reflect the previous (not the current) values. The changes do not take effect until you log off and then log back on.

To effect these changes without having to log off, broadcast a WM_SETTINGCHANGE message to all windows in the system, so that any interested applications (such as Program Manager, Task Manager, Control Panel, and so forth) can perform an update.

MORE INFORMATION

For example, on Windows NT, the following code fragment should propagate the changes to the environment variables used in the Command Prompt: 

   SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 0,
    (LPARAM) "Environment", SMTO_ABORTIFHUNG,
    5000, &dwReturnValue);
None of the applications that ship with Windows 95, including Program Manager and the shell, respond to this message. Thus, while this article can technically be implemented on Windows 95, there is no effect except to notify third-party applications. The only method of changing global environment variables on Windows 95 is to modify the autoexec.bat file and reboot.

Keywords : kbui UsrMisc kbui
Version : 3.1 3.5 3.51 4.0
Platform : NT WINDOWS
Issue type : kbinfo

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Last reviewed: May 27, 1997
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