Parsing a char[] of integers into ints i

Question

I used fgets() to read input of a file into a

char buf[10];

the input of the file is

10,10,4,10

I want to iterate through the line and store each number in the char array as its own individual integer value but I am a little lost on how to do that. If someone could point me in the right direction I'd really appreciate it, thanks!

Use a bigger buffer. `Input "10,10,4,10\n"` needs at least 12 bytes to save as a _string_. Post true code used. — chux - Reinstate Monica, Oct 15 '21 at 03:08
You might want to have a look at [`sscanf`](https://en.cppreference.com/w/c/io/fscanf). — Aconcagua, Oct 15 '21 at 03:09
Or [strtok](https://man7.org/linux/man-pages/man3/strtok.3.html) and [atoi](https://man7.org/linux/man-pages/man3/atoi.3.html). — Jeff Holt, Oct 15 '21 at 03:11
Even more size is needed for a potential additional "10" in place of the "4". — Yunnosch, Oct 15 '21 at 03:11
For array sizes powers of 2 are recommendable anyway – 16 or 32, if numbers with more than 2 digits are involved (or more numbers). — Aconcagua, Oct 15 '21 at 03:22

score 0 · Answer 1 · answered Oct 16 '21 at 18:57

There are different approaches to do this. If you are learning C, I would recommend writing your own by-hand solution and after understanding how it works, use some standard library functions like strtok as @Jeff Holt said.

The easiest approach is to create a variable which will be the current number which we are reading and iterate over the buf array and at each step check if the current character is a number or not.

See this question about converting characters to integers.

So the result will be something like that:

const int size = 10;

char buf[size];
// fill buf, but be sure that input is less than 10 characters

//create array for result
char result[size];
int result_size = 0;

//can also be char, but if input numbers are big enough, it might overflow
int current_value = 0;

for (int i = 0; i < size; i++) {
    if (buf[i] >= '0' && buf[i] <= '9') {
        //convert to int and add to current_value      
    } else {
        //store parsed integer
        result[current_size] = current_value;
        current_size++;
        current_value = 0;
    }
}

Parsing a char[] of integers into ints i

1 Answers1