c - Get scanf to quit when it reads a newline?

Question

If I input 5 5 at the terminal, press enter, and press enter again, I want to exit out of the loop.

int readCoefficents(double complex *c){
    int i = 0;
    double real;
    double img;
    while(scanf("%f %f", &real, &img) == 2)
        c[i++] = real + img * I;


    c[i++] = 1 + 0*I; // most significant coefficient is assumed to be 1
    return i;
}

Obviously, that code isn't doing the job for me (and yes, I know there is a buffer overflow waiting to happen).

scanf won't quit unless I type in a letter (or some non-numeric, not whitespace string). How do I get scanf to quit after reading an empty line?

Answer 1

Use fgets to read console input:

   int res = 2;
   while (res == 2) {
       char buf[100];
       fgets(buf, sizeof(buf), stdin);
       res = sscanf(buf, "%f %f", &real, &img);
       if (res == 2)
           c[i++] = real + img * I;
   }
   c[i++] = 1 + 0*I; // most significant coefficient is assumed to be 1
   return i;