Why EOF(end of file) isn't working at the end of a line without a '\n' before it?

Question

So I started to learn C using the ANSI C book. One of the early exercises in the book is to write a program that takes text input and prints every word on a new line, simple enough. So i did:

#include <stdio.h>

#define IN 1
#define OUT 0

 main() { 

    int c;
    int state;

    state = OUT;

    while((c = getchar()) != EOF){
        if(c != ' ' && c != '\n' && c != '\t'){
            state = IN;
        }else if(state == IN){
            state = OUT;
            putchar('\n');
        }
        if(state == IN)
            putchar(c);
    }

     getchar();
 }

The thing is that while the program works fine it won't break from the while loop if I enter EOF(Ctrl+Z on windows) as the last char of a line or in the middle of it.

So I found an answer here.

What I learned is that the (Ctrl+Z) char is some sort of signal to end the stream and it must be on a new line for getchar() to return EOF. While this is all good and it kinda helped I really want to know why is it necessary for the EOF to be on its own line?

See this answer http://stackoverflow.com/questions/4358728/end-of-file-eof-in-c?rq=1 — Jayesh Bhoi, Jun 30 '14 at 12:02
We had a similar question a few weeks ago, and I couldn't find any references for this. But as far as I remember it for most UNIX-like terminals, `^D` flushes the input buffer and if it is flushed, EOF is sent; a newline also flushes the buffer. Maybe that's the same for Windows (with `^Z` instead of `^D`)? — mafso, Jun 30 '14 at 12:12
Also note, that your last `getchar();` never can read anything (the last `getchar` call returned `EOF` when you exited the loop). — mafso, Jun 30 '14 at 12:13
@mafso The last `getchar()` is there to keep the console open and nothing more. — Dima Maligin, Jun 30 '14 at 12:18
And this works (just out of curiosity, I'm unfamiliar with the Windows console)? — mafso, Jun 30 '14 at 12:21
@Jayesh Well my understanding of your comment was that you linked to a post that answers my question, maybe I misunderstood. — Dima Maligin, Jun 30 '14 at 12:31

hugomg · Accepted Answer · 2014-06-30T12:17:43.840

The problem you are having is related to your command line terminal and has nothing to do with the end of file marker itself. Instead of sending characters to the program as you type them, most terminals will wait until you finish a whole line before sending what you type to the program.

You can test this by having the input come from a text file instead of being typed by hand. You should be able to end the input file without a newline without any problems.

./myprogram.exe < input.txt

By the way, the answer you linked to also points out that EOF is not a character that is actually in your input stream, so there is no way for it to come "before" a "\n". EOF is just the value that getchar returns once there are no characters left to be read.

Yes I understood that `EOF` is not a char what i didn't get is why cant I use(Ctrl+Z) at the end of a line ti signal `getchar()` to return `EOF`, your answer makes since and now I can relax and advance through the book without breaking my brain over that issue! Thank you. — Dima Maligin, Jun 30 '14 at 12:23

score 3 · Answer 2 · edited May 23 '17 at 10:26

When reading from a tty device (such as stdin for a program running in a console or terminal window) the terminal is in so-called cooked mode. In this mode, some level of line editing facilities are provided, allowing the user to backspace and change what has been typed.

The characters that are typed are not returned to the program until after return has been pressed.

It is possible to do this by placing the terminal in 'raw' mode. Unfortunately it seems this is not well standardised though, so it is somewhat system specific. The answers to this question have some examples for various platforms.

Why EOF(end of file) isn't working at the end of a line without a '\n' before it?

2 Answers2

Linked