get first char from *char[] variable in C

Question

i want to get the first character of a string (char[]) in C.

unsigned int N;
unsigned int F;
unsigned int M;
char C;
int main (int argc, char *argv[]){
    if (argc!=5){
        printf("Invalid number of arguments! (5 expected)\n");
        exit(-1);
    }
    N = atoi(argv [1]);
    F = atoi(argv [2]);
    M = atoi(argv [3]);
    C = (char) argv[4]; //this way gives a wrong char value to variable C

The code above gives me the warning: cast to pointer from integer of different size.

EDIT: as pointed in comments, argv is char *[], not char[].

Solution 1

There are two main ways to do this. The first is to simply dereference the pointer.

C = *argv[4];

You can also do it via array subscript, which implicitly adds an offset to the pointer before dereferencing it.

Be sure to check whether it's null first, and so on. In general, you need to be careful when dealing with pointers.

Solution 2

argv[4] is a char array. You need to dereference that array to obtain a single element from it

C = *(argv[4]);

Comments

[Daniel Fischer]

I guess the argc != 5 test counts as checking the validity in this case.