Thread: Confused with -> while(getchar() != newline);

Hi
I don't understand the code

int c, j;
while(scanf("%i", &j) != 1)
while((c = getchar()) != '\n')
;

I read alot of topics and comments about getchar() function and i knew that
getchar() is just a function gets the first character of the line the user entered

Here in our example i understood that the code locks the console screen until the user
hit the enter key ...but when i run the program
->in case i typed 1 the console freezes
and in case i typed anything but 1 the console freezes too ?!

Why ..
could you please explain ..
i'm new with c so be simple as you can ..
thanks

scanf(), fscanf()
%i is just like %d and scanf is returning the number of values assigned to variables
the second while statement is executed until '\n' is encountered. This is the newline character. Or Enter

I understand the scanf() function
and i know that the '\n' means new line but i don't understand the while loop code in total here

I can't reproduce your problem with the code that you posted.

don't care about the whole code
i'm just asking about getchar() function in the while loop


while((c = getchar()) != '\n')
;


what does this specific code mean?
thanks

I'm just concerned because you wrote this:

Here in our example i understood that the code locks the console screen until the user
hit the enter key ...but when i run the program
->in case i typed 1 the console freezes
and in case i typed anything but 1 the console freezes too ?

which told me that you thought the code was doing something wrong.

Yeah I can explain what that line does. It calls getchar() until it returns a newline; when the newline is read, the loop will break. It is the operative code in your explanation here:

i understood that the code locks the console screen until the user
hit the enter key

I would say that the console is "waiting for input" but whatever floats your boat.


I'm really confused as to how you could write that explanation and ask about it, but I hope that you're clear.

Originally Posted by grumpy

In terms of mechanics, it keeps calling getchar() and storing the result in c, until the result is a '\n'.

In terms of net effect, it gobbles characters from standard input until a newline ('\n') is encountered, and leaves a '\n' character in c.

It can also be simplified to this...

Code:

while (getchar() != '\n');

Just a way of finding the end of the current line.

Thanks for all of you guys
I'm really grateful for your interesting

Let me tell you that i'm new with C so let me say what i understood from all your answers

Code:

int main(void)
{
	char c ;
	while((c = getchar()) != '\n');
	printf("Enter a number");
	return 0;
}

**It calls getchar() until it returns a newline

** when the newline is read, the loop will break

**that means when the user hit the enter key and a newline is read the loop will break and the
"Enter a number" will be printed on the screen .

**Then the user can type any thing on the console ... right ?

I'm not sure because when the "Enter a number " appears on my console the console freezes and i can't type any thing .. why?

"Enter a number" will be printed on the screen .

**Then the user can type any thing on the console ... right ?

The program..as it is now.. just exists after asking for the input.

I'm working on ubuntu 11.04