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I'm making somewhat like an othello game. I receive a file that contains strings, and i have to read and process them, making the board as it goes. Example of the file received:

  1. Alejandro,B
  2. Federico,N
  3. B
  4. D6
  5. C4
  6. G5

then i would convert the characters to numbers, so it can fit in the int board[8][8] i use

I was expecting that when it reaches the EOF it would get out of the loop, but instead it never stops the loop and keeps reapeting the last line with the printf. This is in the main function:

while( EOF != 1 && *error != 1)
    {
        tomaJugada(&fp,jugada);  //takes 1 line of the file
        toupper(jugada[0]);      
        int columna = convierte_a_int(jugada[0])-1;  //converts the letter to a number
        int fila =  (jugada[1]-'0')-1;               //converts the char number to int number
        printf("columna %i, fila %i \n",columna, fila);   
    }

This is the auxiliary function:

void tomaJugada(FILE** fp, char jugada[])
{    
    fgets(jugada,5,*fp);
    jugada[2] = '\0';
    //jugada[strcspn(jugada, "\n")] = 0;
}

I have seen people using thi:

int ch = getc(fp);
  while (ch != EOF){...

but it would consumme data that i need to use, maybe i'm using it wrong?

Resumming: i want to use all the data in the file, reach de EOF, and end the loop. How can i put the condition for the EOF?

I hope i explained myself well, i appreciate any help

dumping the core
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    What is `EOF != 1` supposed to do? That will always be true. `EOF` doesn't change and is usually defined as `-1`. – Ted Lyngmo Jan 10 '23 at 15:15
  • `EOF != 1` - what is this? `EOF` is a defined symbol, that is usually comparing to `-1`. This condition is always true. – Eugene Sh. Jan 10 '23 at 15:15
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    `while(tomaJugada(&fp,jugada)) { ... }` would be a sounder loop, where `tomaJugada` returns `true` or `false` depending on if it successfully read and parsed a line. – Ted Lyngmo Jan 10 '23 at 15:19

1 Answers1

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EOF in c is just a constant (typically -1), EOF != 1 would always evaluate to the same (that is guaranteed to be true as EOF will always be negative). What you need to do is to check if fgets returns null pointer (that is in the tomaJugada function) and when that happens, then either an error occurred or you've reached the end of the file. To disambiguate between the two you could use the feof function for instance.

Ivaylo Strandjev
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    A `NULL` pointer returned from `fgets` means that either EOF or an error occurred, and you need to use `feof` and/or `ferror` to distinguish between these cases. – Bodo Jan 10 '23 at 15:21
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    yes, actually good point, a null pointer may be returned when an error occurs too – Ivaylo Strandjev Jan 10 '23 at 15:22
  • Yes, I pointed out that the inequality will always be true, but the value of EOF is typically -1. I will expand on this – Ivaylo Strandjev Jan 10 '23 at 15:29
  • @Bodo Checking `feof()` has an [advantage](https://stackoverflow.com/a/53274876/2410359) over checking `ferror()`. When the _error indicator_ is set before `fgets()` and an end-of-file occurs, `ferror()` and `feof()` both return true, even though the `NULL` return is due to end-of-file. – chux - Reinstate Monica Jan 10 '23 at 15:44
  • Thanks to all for answering and pointing out solutions. Have a great day! – dumping the core Jan 10 '23 at 17:40