C fscanf从不返回EOF

Question

int findMaxAndMinValues(FILE *file)
{
    int current_number, max_number = INT_MIN, min_number = INT_MAX;
    rewind(file);
    while ( fscanf(file, "%d", &current_number)!=EOF )
    {
        printf("%d \n", current_number);
        if (current_number > max_number) max_number = current_number;
        if (current_number < min_number) min_number = current_number;       
    }
    printf("Max: %d, Min: %d\n", max_number, min_number);
    return 0;
}

So this works fine if the text file is only full of numbers (and spaces/newlines accordingly). But if I have a character in it, it starts looping just the last number it read before encountering the character. This is the text file:

1
2
3 4 5
16 
12312
hello  

And the result is just 12312 every line updating endlessly.
Side question: is there a better way to find min/max values of numbers in a text file? Rather than fscanf with %d? EDIT:Thanks to the answer, here's how I fixed it:

int findMaxAndMinValues(FILE *file)
{
    int current_number, max_number = INT_MIN, min_number = INT_MAX;
    int temp;
    rewind(file);
    while ( (temp=fscanf(file, "%d", &current_number))!=EOF )
    {
        if (!temp) { fgetc(file); }
        else {
            printf("%d \n", current_number);
            if (current_number > max_number) max_number = current_number;
            if (current_number < min_number) min_number = current_number;
        }
    }
    printf("Max: %d, Min: %d\n", max_number, min_number);
    return 0;
}

Answer 1

Read the man page. fscanf() can return other values besides EOF . In particular, if a conversion fails — in particular, if fscanf() encounters a non-numeric character — it will return zero to indicate that nothing was read.

You need to act on this information. Otherwise it will return zero the next time as well. And the time after that, ad infinitum.

Answer 2

The reason your code loops indefinitely if the program input contains a non-number is that fscanf() does not consume input it fails to match, but neither does it return EOF in the event of a matching failure. EOF is returned only in the event that the end of the input is reached before either a successful conversion is performed or a matching failure occurs, or if a read error occurs. (A read error is an I/O error -- quite a different thing from a matching failure .) When your particular program experiences a matching failure, it just loops back around and tries reading the very same input (left waiting to be read) again.

One way to solve the problem would be to compare fscanf() 's return value with the number of items expected (1), and break from the loop if you see anything else, whether EOF , 0 , or whatever:

while ( fscanf(file, "%d", &current_number) == 1 ) // ...

Your program would then stop reading numbers when it encounters a non-number; if you instead wanted it to skip non-numbers then that could be done, too, but it would be a bit more complicated.