Since this is for your System Programming course, I won't give you the exact answer here, but I can definately give you enough to help
"..teach a man to fish.."
cjf, myself, and others discussed this briefly on the CB soon after it was posted, and I gave up a few ideas on how to solve this. First a few key questions have to be asked:
- Will you have access to create character devices on the target machine?
- Will you be able to rebuild a kernel or reboot the kernel on the target machine?
- Can you run a daemon on the user machine, global to all processes?
- Are you limited to using pure perl? Or can you use C also?
With this, you could begin to construct several plans of attack:
- Write a kernel module (does not require a reboot, but requires sufficient access to load it into userspace) which will log all calls through the kernel keyboard driver to a file via normal kernel printk() mechanisms.
- Create a character device in /dev that you can peek from and write to a file (requires root access to create devices)
- Set up a userspace daemon that polls for input, a 'shim' between keyboard driver and input application.
- Work with Inline::C and integrate it with your perl code
Some other modules you may be able to use at your disposal are:
- Net::Daemon to create your daemon process in userspace.
- IPC::open3 to allow you to open a process for for reading/writing/error reporting
- Standard pipe() function for opening and dealing with your system calls..
- The source to xev, the X Event Interface could give you some ideas also
