CODEWITHSUNDEEP
cfile-ioeof
Kakarotto
Kakarotto

Reputation: 65

How to use EOF to read all data from file

I'm learning about file i/o in C language and I wrote this program that reads a file, and then for every even number found, it has to print * to the screen.

My problem is that my program keeps printing * forever.

I have tried different ways,some from this website, but I can't seem to understand how to read until end of a text file using EOF.

I want to learn how to read a text file until the end of the file please. How do I read until the end of a text file? EOF in C.


int main(void)
 {

     int num;
     FILE *ifp;

     ifp = fopen("numbers.txt", "r" );

     if(ifp == NULL)
     {
         exit(1);
     }

     do
     {
         fscanf(ifp, "%d", &num);       

            if(num%2 == 0)

                {
                printf("*\n");
                }
        } while(num != EOF);


    fclose(ifp);

    return 0;
}

Upvotes: 1

Views: 435

Answers (4)

Joseph Pilliner
Joseph Pilliner

Reputation: 71

It's doing this because while(num != EOF) is testing whether int num, the number read from the file, is EOF, rather than whether the end of file has been reached.

To test whether the EOF flag has been set on FILE *ifp, use while(!feof(ifp)) instead.

Upvotes: 0

Catch22
Catch22

Reputation: 401

Have you tried this:

while (!feof(ifp)) {
   if (fscanf(ifp, "%d ", &num) > 0) {
      if(num % 2 != 0) // For every odd number.
                {
                printf("*\n");
                }
   }
}

Upvotes: 0

Shubham
Shubham

Reputation: 1153

Instead, you should try while loop.

#include <stdio.h>
#include <stdlib.h>

int main(void)
 {

     int num;
     FILE *ifp;

     ifp = fopen("numbers.txt", "r" );

     if(ifp == NULL)
     {
         perror("Read");
         exit(1);
     }

     while(fscanf(ifp, "%d ", &num) != EOF)
     {

         if(num % 2 != 0) // For every odd number.

                {
                printf("*\n");
                }
     }
    fclose(ifp);

    return 0;
}

Upvotes: 0

0___________
0___________

Reputation: 67546

you need to check the result of the scanf

     do
     {
         int result;
         result = fscanf(ifp, "%d", &num);       
         if(result == EOF) break;

         if(result != 1) 
         {
             printf("scanf error\n");
             break;
         }
         if(num%2 == 0)
         {
              printf("*\n");
         }
      } while(1);

Upvotes: 2

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