cin.getline - flushing input stream

Martyr

How do some of you using cin.getline do away with excess characters.
I have this problem where i get a name of person from the console,
something like below, and the max size of input buffer is 20 bytes.

	for(int i = 0; i < 3; i++)
	{
		gotoxy(1,7); cout << "Enter user number " << (i + 1) << ":";
		cin.getline(user_struct[i].user_name,20,'\n');
	}

The problem is that, if the person enters 30 characters, the
next call to cin.getline returns those 10 characters after the first 20.
I want to avoid this.

Is there some way to flush these out of the input stream, do away with them?
before the next call?
I asked some programmer already, and he says "its not important",
i think maybe because he didn't know.
but i'd like to know anyway.

daymobrew

Two options (though I don't know much istream):
1) Make the streamsize (2nd param) bigger than the data will ever be.
Then extract the required chars from that (strncpy or the like).

2) istream::ignore (Extracts characters from input stream and discards them)
http://www.cplusplus.com/ref/iostream/istream/ignore.html
Looks like you can read chars up to the specified EOL char ('\n' presumably).
This will 'eat' the unwanted chars.

Of course, both of these solutions will suffer from buffer overflow errors if too much data is thrown at them.

jessy

look into the function fflush();

Martyr

Thanks for input lads.
I looked around for info on this.

Some suggestions were to repeatedly use getchar() or cin.getc()
until a newline..but i didn't think this was much good.

fflush() doesn't work apparently.
i tried something like fflush(stdin);

I found that cin.sync() was best solution to problem.
you just call it afterwards and it clears any excess characters
in the istream.

char buffer[5]

cin.getline(buffer,5);
cin.sync();