In C how to get number of items in array of pointers to char strings

Question

I want to implement the following function to print the contents of several char strings which are referenced through a pointer array. How can I determine how

Answer 1

There is no built-in way to do this as C does not track the number of elements in an array for you like this.

You have a couple of options:

1. Pass the number of items in the array.
2. Set the last item to NULL so the code knows when it's reached the end. (This is kind of how C strings are handled.)
3. Otherwise modify your data structures to track the number of items in the array.

Answer 2

You cannot pass arrays as function arguments in C. Array names decay to pointers to their first element when used as a function argument, and you must separately specify the number of available array elements.

(In the context of a function parameter type, T[] and T* and T[12] are identical, so your function paramter might as well be char ** arr.)

Like so:

void printCharArray(char ** arr, size_t len) { /* ... */ }

int main()
{
    char * arr[10] = { "Hello", "World", /* ... */ };

    printCharArray(arr, sizeof(arr)/sizeof(*arr));
}

(Alternatively you can supply a "first" and a "one-past-the-end" pointer, which might be a bit more natural.)

Answer 3

If you set the element after the last valid element to null then you can do:

void printCharArray(char *arr[]){

    for (int i=0; arr[i] != NULL; i++) {
        printf("Array item: [%s]",arr[i]);
    }

}

Answer 4

void printCharArray(char *arr[]) {
    int length = sizeof(arr) / sizeof(char*); /* this does not give correct 
                                                 number of items in the pointer array */
    for (int i=0;i<=length; i++) {
        printf("Array item: [%s]",arr[i]);
    }
}

int main()
{
    char * arr[10] = { "Hello", "World", /* ... */ };
    printCharArray(arr); 
}

Answer 5

first I declared y as a global var. htmTags is a *char[]. then in main()

y = 0;
while( htmTags[y] ) {
        y++;
}

I did not add null at the end of array. provides actual count of array elements

or this works too for (y=0;htmTags[y];y++) ;