How to know when a user opens a file associated with my application?

[snow 56767]

I have a problem that I don't really know how to phrase, so I'll put it in an example:

My application writes a file to a user's hard-drive, the user then, on another day perhaps, double-clicks the file to open it. This file is associated with my application, and I need to open this file but I don't know what the full path to the file was. How can I find out what file the user opened that then launched my application?

Also, this may affect the answer (or not, I don't know) but I am using QT 4.6.2
on Windows compiling with MinGW (I can switch to MSVC 9 if necessary)

[kbw]

It's passed as a command line argument.

[o1vk4iN6]

User needs to set file association to your program in windows.

[LB]

From Wikipedia: http://en.wikipedia.org/wiki/Main_function#C_and_C.2B.2B
Define your main function like this:

int main(int argc, char *argv[])
{
    //...
}

argc is the number of arguments, and argv is an array of character arrays. The first character array is always the pathname of your program, the rest are arguments which in your case are the filenames opened with your application. You can rename argc and argv to any name you want; they're just parameters as with any other function.