Summary

Symptoms

When setting an environment variable during the installation, such as with the Environment Variables view, the new or updated variables do not appear during the installation process, for example, when a custom action may try to access the variables.

Cause

This behavior is due to how environment variables are handled by the Windows operating system and the Microsoft Windows Installer engine. Environment variables set during the installation are not available until the installation exits.

Workaround

Due to this limitation, it is not possible to launch a custom action during the installation and be able to access the new or updated environment variables. A process would need to be launch after the installation process has exited to receive the new variables.

Additional Information