Thread: Dereferencing double pointers

Hello!

I have a variable that points to a character, i.e.

Code:

char* ptr = &characterInArray;

Now I want to send the adress of the ptr-variable into a function so I can modify where it points, but my problem is that I don't know how I am supposed to check the adress before what ptr points to. I have tried this for example:

Code:

if (**(ptr - 1) == token)
    //Do something;

How should I proceed?

EDIT: To clearify, if ptr points to a character in an array I want to check the previous value in the array by using the pointer.