Buffered input

[BlaX]

Hello everyone,
I was trying this very simple piece of code on my Linux machine (running ubuntu 9.10)

#include <stdio.h>

int main(void){
	char c;
	
	while((c=getchar())!=EOF)
	putchar(c);
	
	return 0;
}

When I run this program and input

test<CTRL+D>

i get the my input back

testtest

how is this possible ? The input is buffered, meaning that input should be available to the function after pressing enter ENTER button

Also after running the program and by just pressing <CTRL+D> the program is exiting. Shouldn't it exit after pressing the enter button? Because it is after pressing the enter key the input will be read by the getchar() ?

Thank you

[Dino]

Did you consider that your output might be buffered too?

[BlaX]

I didn't get you.
Can you please explain what is happening ?

[Dino]

What is happening is you are posting twice in the same forum for the same topic and sending private messages to get help. Impatient, are we?

[BlaX]

Oh you replied in the Linux thread. What do you mean my output is buffered?

I added fflush(stdout) under putchar(c) and the results are the same.

so the code is now

#include <stdio.h>

int main(void){
	int c;
	
	while((c=getchar())!=EOF){
	putchar(c);
	fflush(stdout);}
	
	printf("\nha\n");
	return 0;
}

No i dont think it is buffered, because when i input for example 123 and i press enter it gets printed after pressing.

[BlaX]

Let me clarify what I said in my first post, and where my problem is

Let me again explain to you what my problem is.

When I input test<ENTER>, test gets printed on the other line

test
test

Continuing, inputing test<pressing CTRL+D> i get the same thing next to it

test<CTRL+D>test

Pressing <CTRL+D>

it exits the program.

Shouldn't typing test<CTRL+D> do nothing ? Meaning it should wait for the ENTER button to be pressed to read the input ?

[nadroj]

"CTRL+C" is a special character to send an interrupt to the program, usually causing it to exit. "CTRL+D" is another special character, read about it here Definition: end-of-transmission character or elsewhere. So pressing this key may be like the program getting an "EOF" which is why the program would exit.

[laserlight]

I have merged the two threads. Please do not repeat your threads again. There is no need to message people to ask them to look at your thread.

[jeffcobb]

Yeah why are you hitting people up in private messages and cross-posting? This is not the way to get help. It seems folks are trying to help you and you are not accepting the help being offered...

As for your question I am not getting what you don't understand about the code you wrote...you cannot figure out why the while() loop broke? You set the condition yourself by watching for an EOF character, then supplying it...

[BlaX]

All right. My mistake.
As for my question, i know pressing CTRL-D should signal EOF. But my question is, when I input a word, like test for exmple and press CTRL-D, it gets automatically outputed like

(what happens in console, italic is the output)

$./test
test<CTRL+D>test

123<ENTER>
123
<CTRL+D>
PROGRAM EXITS

My question is, knowing that getchar() uses buffer, meaning, all what is input will be available to it after pressing ENTER, why is it that when i type test<CTRL+D> without pressing enter i get test as output and i can continue inputting... so what is CTRL+D doing here? What is wrong ?
Thank you

[Salem]

It means that if there is data already in the buffer, that buffer is considered "complete" without having to press return.

Similarly, you might just get the buffer if you type in a lot of data without pressing return.

ctrl-d returning EOF is only special when there is NO data in the buffer to begin with.