How to run a process from memory/RAM as the "current working directory"

Question

In Java 6 on Windows, I am interested in performing the following task, but really not sure how to go about it.

1. I want to take a zip file
2. unzip its contents into a spot in memory/RAM
3. Create a Java Process that will run a .EXE file that exists within that ZIP file
4. That .EXE must be run while the current working directory is that location in the RAM
5. I will then need to put another file into that same "current working directory" location space in the RAM.

I know it sounds weird, but it will actually make something much more efficient by doing it this way, so if its possible, it would be great to know.

Answer 1

It sounds difficult, and it will definitely require a lot of stuff that cannot be done in pure Java.

On Linux, I think you would need to do the following:

• Create and mount a "tmpfs" - https://unix.stackexchange.com/questions/66329/creating-a-ram-disk-on-linux

• Unzip the ZIP file into the tmpfs

• Run the .exe using ProcessBuilder ... which allows you to set the child processes current directory.

• etcetera

• Unmount the "tmpfs" when you've done.

The commands for creating the "ram disk" file system will be OS specific, and may require root / administrator privilege.

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It is unclear whether doing this will be more efficient than using a temporary directory in the file system. I wouldn't attempt this unless there was a clearly demonstrated need for a solution that it more efficient; i.e. unless you've tried using a temporary directory and found that it is too slow.

Bear in mind that:

• much (maybe most) of the work of unpacking the ZIP file has to be done either way you do it, and

• in the conventional case your .exe will probably be reading the files from the expanded ZIP out of the OS'es in-memory disk-block cache (on Linux).