Reading integers from a text file and adding them (C)

Question

I am a beginner in C programming. I am currently preparing for an exam and I'm stuck on a program. The task is to read from a text file and make the sum of the integers inside it. The file also contains characters. I have tried this as a solution, and it is nearly correct, but it sometimes adds an integer too many times.

void calculate(char* file_name) {
    FILE* file;
    int sum = 0;
    int number;

    file = fopen(file_name, "r");
    char c;

    while ((c = fgetc(file)) != EOF) {
    if (fscanf(file, "%d", &number)) {
        printf("The number is %i\n  ", number);
        sum = suma + number;
    }   
    }   
    fclose(file);
    printf("The sum is %i\n", sum);
}

For example, the text in the file is:

         asdd12 ddd15 dddgh51hh3
         3adb jk !!!*

The sum should be 84 for this file, but it prints 87. Is my method completely wrong or should I just change something in the code?

Thank you in advance for your help.

Answer 1

... should I just change something in the code?

while((c=fgetc(file))!=EOF) does nothing with c and so loses a potential character of numeric input.

if( fscanf(file, "%d", &number)) is a problem as is gets fooled when end-of-file occurs as fscanf() returned non-zero and so code thinks a number was read.

Instead try a 3-way branch. Use the result value from fscanf() to guide the next steps.

int conversion_count;
do {
  conversion_count = fscanf(file, "%d", &number);
  if (conversion_count == 1) {
    // scanf() found an `int`
    printf("The number is %i\n  ", number);
    sum = sum + number;
  } else if (conversion_count == 0) {
    // scanf() failed to finf an `int`.
    // Offending non-numeric input remains in `file`.
    // Read non-numeric input character and quietly toss it.
    fgetc(file); // 
  }
} while (conversion_count != EOF);

Alternative: Robust code would read a line of text with fgets() and strtol() to look for integers.