How to stop reading a txt file at the end of it - c

Question

I'm writing a C program which reads a text file line by line with a certain format to it.
I made a do { ... } while(!feof(file)); loop but it always loops one too many times. This is an issue because I have made it so that when my program expects to read something but gets nothing, it throws an error, so now it is throwing an error every time because it reaches the end of the file at the top of my loop.
I figured this is because the eof flag is triggered only once you try to fscanf something but there is nothing there. How can I fix this problem? Putting a final fscanf at the bottom doesn't work because if it's not at the end of the file, it will mess all the readings up and shift everything by one.
do {
read = fscanf(/*...*/);
if (read != 1)
{
return -1;
}
// Read grades
read = fscanf(/*...*/);
if (read != 3)
{
return -1;
}
// Read student kind
int student_kind = 0;
read = fscanf(/*...*/);
if (read != 1)
{
return -1;
}
if (student_kind < 0 | student_kind > 2)
{
printf("Invalid student kind");
return -1;
}
SCIPER sciper_teammate = 0;
read = fscanf(/*...*/);
if (read != 1)
{
return -1;
}
} while (!feof(file));

Answer 1

Since you are using fscanf():
ISO/IEC 9899:2017
§ 7.21.6.2 - 16 - The fscanf function returns the value of the macro EOF if an input failure occurs before the first conversion (if any) has completed. Otherwise, the function returns the number of input items assigned, which can be fewer than provided for, or even zero, in the event of an early matching failure.
EOF is a macro with the value of -1, by itself it's not distinguishable as for the reasons why it occurs.
For this distinction § 7.21.6.2 - 19 recommends the use of feof() for end-of-file and ferror() for I/O error:
EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
#include<stdio.h>
/*...*/
int count; floatquant;
charunits[21], item[21];
do {
count = fscanf(stdin, "%f%20sof%20s", &quant, units, item);
fscanf(stdin,"%*[^\n]"); //here discarding unread characters in the buffer
} while(!feof(stdin) && !ferror(stdin));
This should work in your case but personaly. I don't like this approach since if you input less values than what fscanf is expecting this will fail, normaly resulting in an infinite loop.
My approach when reading formated input, is to check the inputed values.
For a sample input of 2 integers you can do something like:
Live sample
#include <stdio.h>
int main()
{
int a, b;
FILE* file;
if(!(file = fopen("file.txt", "r"))){
return 1;
}
while(fscanf(file, "%d %d", &a, &b) == 2){ //read each 2 integers in the file, stop when condition fails, i.e. there are nothing else to read or the read input is not an integer
printf("%d %d\n", a, b);
}
}
This addresses all input failures and will end the cycle for I/O error, for EOF and for bad inputs.