How to change the actual argument passed to a function in C?

Question

I want to change the actual argument passed to a function and not a copy of it. For example:

char str[] = \"This is a string\";

I want to c

Answer 1

To change a string passed to a function in-place, use a regular pointer. For example:

void lower_first_char(char *str)
{
    *str = tolower(*str);
}

After this function executes, the first character of the passed string will be changed to lowercase.