Question

I have a pointer to a char array. I want to increase it until it will not point at a digit / number (represented as a char in the char array).

For example, if pointer points to '2' in this char array:

['1'][' ']['2']['3']['4'][' '][' '][' ']['5']['6']['7']
            ^
         *pointer

I want to increase it until it will point at the first non-digit character – ' ':

['1'][' ']['2']['3']['4'][' '][' '][' ']['5']['6']['7']
                           ^
                        *pointer

I know I can do something like this:

while (*pointer == '0' || *pointer == '1' || *pointer == '2' || ...)
    pointer++;

return pointer;

but it’s pretty long and not elegant at all.

I thought I could use atoi(), which returns 0 when the pointer doesn’t point at a number:

while (atoi(pointer) != 0 || *pointer == '0') //while it still points at a number
    pointer++; //increase the pointer until it will not point at a number

return pointer;

But it doesn’t seem to work. Maybe it’s okay and I have a mistake somewhere else, but anyway I wanted to know:

Are there are any other (better) ways to check whether a pointer to a char array points at a digit / number and increase it until it will point at a non-digit character, in C?

Answer 1

You should probably use isdigit from ctype.h instead. Something like:

while (*pointer && isdigit(*pointer))
    pointer++;