How to convert String to int in C

I have following thing which i wanted to convert to int.

char *ptr; // this can point to variable length of string

int balance = functionToConverIntoint(ptr)

So is there any such function in C 开发者_开发知识库"functionToConverIntoint" which can do this job?

Check out strtol() and strtoul().

You want to avoid atoi() as it does not have a good way of distinguishing between a string of "0" and an invalid number.

Yes. atoi is a basic one with very limited error handling capability; strtol is a better one.

There's also sscanf().

balance = atoi(ptr)