无法正确将双数导入C程序

Question

I have a txt file formatted this way:

MyDepartureTown MyDestinationTown 123.45 Vehicle 12

I am trying to import the data into my C program. Here it is the code I am using to acheive just that:

void import_city_info(Grafo *G)
{
    char city_dep[20];
    char city_des[20];
    double km;
    char vehicle[12];
    int time;

    FILE *data_file = fopen("data/routes.txt", "r");
    if (data_file == NULL)
    {
        fprintf(stderr, "Errore. Impossibile aprire il file.\n");
        exit(EXIT_FAILURE);
    }

    while (5 == fscanf(data_file, "%s %s %f %s %d", &city_dep, &city_des, &km, &vehicle, &time))
    {
        printf("%2.3f\n", km);
        //more code...

    }
}

As I try to print out the double numbers, it outputs 0.00 . It's actually importing correctly all the data except the double. What am I doing wrong?

Answer 1

You are using a wrong specifier to read double . This will invoke undefined behavior. You need %lf .

while (5 == fscanf(data_file, "%s %s %lf %s %d", &city_dep, &city_des, &km, &vehicle, &time))
{