Programmatically adding a directory to Windows PATH environment variable

Question

I\'m writing a Win32 DLL with a function that adds a directory to the Windows PATH environment variable (to be used in an installer).

Looking at the environment vari

Answer 1

It turns out there really isn't anything new under the sun. This has already been done before, at least once. By me. I created a DLL very much like what you describe for exactly the same purpose (for use in modifying the path from an NSIS installer). It gets used by the Visual Leak Detector installer.

The DLL is called editenv.dll. The source is available at github. I just tested the installer and it updated the system PATH environment variable, no problem. Based on what you've written, I don't see anything that stands out as being wrong. I also don't see anything obvious that's missing. But it may be worth a look at the editenv.dll source (you'd be most interested in EnvVar::set() in EnvVar.cpp, and possibly the pathAdd() and pathRemove() C APIs in editenv.cpp).

Answer 2

I have a program which calls the same Win32 API to yours to update the environment, and it works fine.

One thing to be careful of is how you are opening up the command prompt.

If you open up the command prompt by doing this:

Start -> Run -> cmd.exe

then the environment in the prompt shows that the new variable is set.

However, I also have a programmable function key on my keyboard which I have set to run the cmd.exe process. If I open a command prompt via that function key and then type env, it doesn't show the variable as being set.

I'm not sure why it works differently, but it must have something to do with the way the cmd.exe process is launched (although both are running under my user name, not SYSTEM).

How are you opening up the command prompt?