如何从C中的.txt文件读取数字

Question

How can you make it so the program reads only the numbers in a string from a .txt file? This is so you can then store them and use them for later transformations.

I think I know how to do it if it were numbers only, like if you had a file that had "0.3 0.4":

fscanf(fp, "%f %f\n", &x, &y);

Or if it were a string that was always the same in each line. Example, in a file, there's several lines like this one: "sin(0.348889)=0.341854". Then to read the numbers you'd only have to do something like this:

fscanf(fp, "sin(%f)=%f\n", &x, &y);

But how do you do you do it when the strings are not always the same? How to read certain numbers from that file? I know this is way too much to ask, but reading the book isn't helping me and I already tried searching in the internet, so I decided to take the shot..

Answer 1

You can skip not numbers from string by reading chars. Something like this:

int n;
float number;
errno = 0;
while (!errno) {
    n = fscanf(fp, "%f", &number);
    if (n == 1) {
        /* do something with number */
    } else {
        char c;
        n = fscanf(fp, "%c", &c);
        if (n != 1) { /* EOF */
            break;
        }
    }
}