How to find out with which parameter the program is launched?

Question

Windows

Hey toaster.
You've helped me before, I hope you can help me this time too.
The situation is as follows: program 1 starts program 2 with some parameter (after all, it can only pass some information to it with a parameter, right?). How to find out which one?
OS - Windows, PL - C#

Answer 1

Thanks to those who answered. Process Monitor helped with the problem.

Answer 2

No programming language or OS specified. Therefore - GetCommandLine().
PS. Command line options are far from the only IPC method. There are at least Pipe, Socket, Shared Memory.