Read a line from file in C and extract the number of input

Question

I have a file input.dat. In this file, there are 3 lines:

1 2 3
5 7 10 12
8 9 14 13 15 17

I am going to read one of the three li

Answer 1

the loop while (sscanf(line, "%d ", &number)) keeps parsing the first number in the line.

You should use strtol instead:

#include 
#include 

#define STRING_SIZE 2000

int main() {
    FILE *fp = fopen("in.dat", "r");
    char line[STRING_SIZE];
    int lcount = 0, nline = 1;

    if (fp != NULL) {
        while (fgets(line, STRING_SIZE, fp) != NULL) {
            if (lcount == nline) {
                char *p = line, *q;
                int count = 0;
                for (;;) {
                    long val = strtol(p, &q, 0);    // parse an integer
                    if (q == p) {
                        // end of string or not a number
                        break;
                    }
                    // value was read into val. You can use it for whatever purpose
                    count++;
                    p = q;
                }
                printf("%d\n", count);
                break;
            } else {
                lcount++;
            }
        }
        fclose(fp);
    }
    return 0;
}