converting a string into a double

Question

I am looking for a way to get floating point input from a user.

My way of going about this is to use a self-made getstrn function and plug that into another function which would convert the string into a double.

My safe get string:

void safeGetString(char arr[], int limit){
    int c, i;
    i = 0;
    c = getchar();
    while (c != '\n'){
        if (i < limit -1){
            arr[i] = c;
            i++;
        }
        c = getchar();
    }
    arr[i] = '\0';
}

What would be the best way to write this get_double function?

Answer 1

Try the strtod function:

char *end;
double num = strtod(arr, &end);

The end will point after the last char that was processed. You can set the second to NULL if you don't care about that. Or you can use atof: atof(str) is equivalent to strtod(str, (char **)NULL).

But you should care, since you can check if the input is malformed:

if (*end != '\0')
  // Handle malformed input