Wrote a program that counts the number of lines in a text file.

It calculates the lines correctly, but after I added a check for a file read error, the program for some reason displays an error message 47 times, and then still displays the correct result (by the way, there are only 25 characters in the file (not counting any control characters like \ n) and 21 lines). What’s the problem?

# include & lt; stdio.h & gt;
int main () {
  FILE * file;
  file = fopen ("C: /c/fff.txt", "r");
  if (file == NULL) {
    puts ("Error opening file.");
  }
  int lines = 1;
  while (! feof (file)) {// loop counting the number of lines in the file
    if (feof (file) == 0) {// check for file reading error
      puts ("Error reading.");
    }
    if (fgetc (file) == '\ n') {
      lines ++;
    }
  }
  printf ("% i", lines);
  fclose (file);
  return 0;
}

Answer 1

The feof function checks if the end of the file has been reached. Returns 0 if not is reached and not zero otherwise.

Which means that the line if (feof (file) == 0) inside while (! feof (file)) is absolutely meaningless. If you go inside while , then the end of the file has not yet been reached.

Answer 2

As I understand it, the correct check for a file read error should look like this.

int c;
while (! feof (file)) {// loop counting the number of lines in the file
  c = fgetc (file);
  if (c == '\ n') {
    lines ++;
  }
}
if (c == EOF & amp; & amp; feof (file) == 0) {// check for file reading error
  puts ("Error reading");
}