File writing in C

Question

I'm trying to write data into a file using C. I wrote the below code.

#include<stdio.h>

void main(){

    FILE *f1;
    char c;

    printf("Data Input\n\n");
    f1 = fopen("INPUT", "w");

    while((c = getchar()) != EOF)   putc(c, f1);

    fclose(f1);

    printf("\nData Output\n\n");
    f1 = fopen("INPUT", "r");

    while((c=getc(f1)) != EOF)  printf("%c", c);
    fclose(f1);

}

But the code is behaving abnormally. The below pic is the output.

I had to enter EOF three times to make it work. I don't understand why this is happening. Is there any error in my code? I'm using Dev-C++ 5.6.3

Thanks in advance.

**Note:** `void main()` is an anachronism. The proper definitions of `main()` are `int main (void)` and `int main (int argc, char **argv)`. You will also see the equivalent, and proper, `int main (int argc, char *argv[])`. There are non-standard OS specific parameter extensions, e.g. `char **envp`, but those should not be used for portable code. — David C. Rankin, Mar 10 '17 at 14:26
Why do you use `putc` to write to f1, but `printf` to write to stdout? It would be more consistent to use `putc(c, stdout)` — William Pursell, Mar 10 '17 at 14:27

score 1 · Answer 1 · answered Mar 10 '17 at 14:20

1

If char is unsigned on your platform it cannot store EOF and the comparison will never become true.

Change

char c;

to

int c;

answered Mar 10 '17 at 14:20

Klas Lindbäck

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File writing in C

1 Answers1