Question

I am writing a program in which stdin is read into a buffer, then processed. The vast majority of these items that need to be processed are strings (or well, character arrays). However, I do have one item that needs to be read in as a character array and then converted to int for ease of use in the future.

for(i=0; i<n; i++){
    num[i] = buff[(i)];
    printf("%c", num[i]);
}

convert = atoi(num);

So I know for sure that the correct group of characters is being read into num because the printf for that is correct. However, when I try to print convert I end up getting 0, and I’m very perplexed as to what I’m doing wrong. I know that the 0 return means that a valid conversion could not be performed, but I don’t know what’s making it invalid. Any tips?

EDIT: Sorry for not including these before >_<

n is the number of chars in the buff array
buff is the buffer array stdin is read into

Answer 1

atoi is a function that gives you no means to analyze error conditions. On top of that, it produces undefined behavior in overflow situations. Don’t ever use atoi (or atof or anything from ato... group) in real-life programs. It is practically useless.

To perform string-to-number conversions use strtol (and other functions from strto... group).

Now, what is inside your num at the moment you call your atoi? Is your num properly zero-terminated?