Java - The system cannot find the file specified when using ProcessBuilder directory()

Question

I'm trying to run a child process in Java while using ProcessBuilder's directory() method. However, whenever I use the directory() method, the program fails, saying the file was not found. However, the file is present in the working directory.

Process process = new ProcessBuilder("firefox")
                    .directory(new File("C:\\Program Files\\Mozilla Firefox"))
                    .inheritIO()
                    .start();

Output:

Could not start server due to java.io.IOException: Cannot run program "firefox" (in directory "C:\Program Files\Mozilla Firefox"): CreateProcess error=2, The system cannot find the file specified

When I ommit the directory() method and create a ProcessBuilder like: new ProcessBuilder("C:\\Program Files\\Mozilla Firefox\\firefox"), it works fine and firefox.exe launches successfully.

This happens both on Windows and Linux.

I've already tried several versions of the launch command (like firefox, firefox.exe, ./firefox, ./firefox.exe) but with no success.

Answer 1

Figured it out

I didn't realize that the directory() method only sets the working directory for the new child process and you still need to provide a full path for the executable you want to run.

In this case, the following code would work:

Process process = new ProcessBuilder("C:\\Program Files\\Mozilla Firefox\\firefox")
                    .directory(new File("C:\\Program Files\\Mozilla Firefox"))
                    .inheritIO()
                    .start();