C, read from file into array, number by number

Question

void readfromFile() {

    FILE *myFile;
    myFile = fopen("matrikel.txt", "r");

    //read file into array
    int numberArray[12];
    int i;

    if (myFile == NULL) {
        printf("Error Reading File\n");
        exit (0);
    }

    for (i = 0; i < 12; i++) {
        fscanf(myFile, "%d,", &numberArray[i] );
    }

    for (i = 0; i < 1; i++) {
        printf("Number is: %d\n\n", numberArray[i]);
    }

    fclose(myFile);
}

"matrikel.txt" contains

808098822790

The number seems to be too long for the int numberArray[12], when running the code it prints a random number. When cutting some of the single integers from the end of the number it works, the maximum length seems to be 9.

I'm not quite sure but shouldn't the fscanf in the first for loop print one single digit number into each cell of numberArray[]?

You use the format "%d," for reading the numbers, that expects each number to have a comma after it. Perhaps you want to read each digit separately instead? Then I suggest you read each digit as a character instead, and then convert that character to its corresponding int value instead. — Some programmer dude
– Some programmer dude, Commented Jan 11, 2018 at 12:28
@Someprogrammerdude Okay, sounds like what I was wanting to do, but how can I? I was told to use an array, can I read each digit as a char into an array? — nb99
– nb99, Commented Jan 11, 2018 at 12:31
Why not read each digit, as a character, into a char variable? Then convert it (by doing e.g. char_variable - '0') and store that value in the int array you have? — Some programmer dude
– Some programmer dude, Commented Jan 11, 2018 at 12:33
I'm still not quite sure how to get it done, what I just tried didn't work. I will take a look at your idea when I have time, later today. Thanks for the idea :) — nb99
– nb99, Commented Jan 11, 2018 at 12:43

LucaLumetti · Accepted Answer · 2018-01-11 12:48:16Z

5

A format specifier for scanf follows this prototype: %[*][width][length]specifier So, with %1d you will read a single number each time. But would be more simple to read each number as a char with fgetc(myFile);

 for (i = 0; i < 12; i++) {
     int c = fgetc(myFile);
     if(c == EOF)
        break;
     numberArray[i] = c - '0';
 }

edited Jan 11, 2018 at 12:48

answered Jan 11, 2018 at 12:43

LucaLumetti

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1 Comment

nb99 Over a year ago

I will look into your post later, thanks for providing me with some answers

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