fscanf - I don't know what I'm doing wrong here

Question

 char id;
 int num, r;
 if (argc != 2) {
   printf("error\n");
   exit(1);
 }

 FILE *file = fopen(argv[1], "r");
 if (file == NULL) {
   printf("error\n");
   exit(1);
  }

  while ((r = fscanf(file, "%c\t%d", &id, &num)) != EOF) {
    if(r == 2) {
      printf("id: %c, value: %d\n", id, num);
    }
    else if (r!=2) {
      printf("bad input\n");
    }
  } 

The file I'm trying to read looks like:

i 10

i 12

d 10

d 12

(The character/integer are tab separated). My output is:

id: i, value: 10

bad input

id: i, value: 12

bad input

id: d, value: 10

bad input

id: d, value: 12

bad input

WHAT am I doing wrong? "Bad input" should ONLY be printed if the file is incorrectly formatted. The file above demonstrates a properly formatted file. I don't understand how r == 2 and r != 2 at the same time (both conditions are somehow met).

Answer 1

Use

while((r = fscanf(file, " %c\t%d", &id, &num)) != EOF)  //Whitespace before %c 

Might solve your problem. Because when you use

fscanf(file, "%c\t%d", &id, &num)

Then it leaves a newline character which is consumed in the next iteration. As your next iteration your id get \n and num gets the character.

But when you put extra white space before %c which tells fscanf() to ignore whitespaces(including Tab, space or newline). Thus your fscanf() gets two parameter(character and number).

Answer 2

Please change

while ((r = fscanf(file, "%c\t%d", &id, &num)) != EOF) {

to

 while ((r = fscanf(file, "%c\t%d\n", &id, &num)) != EOF) {

Adding \n at the end in fscanf.

In your file, lines are terminated with \n. In next read it does not go well.