C Disable command-line input

Question

I'm creating a ncurses program which reads system-wide keystrokes using AppKit. To clear the wall of text that accumulates on the command line while I run the program I execute this line of code before exiting the program.

while((c = getch()) != '\n' && c != EOF) {}

My question is if there is a more efficient way to solve this. For example disabling command line input while the program executes.

Edit:

I ran some tests and my problem seems to be rooted in usleep and not ncurses or AppKit. Here is an example:

#include <unistd.h>

int main() {
    usleep(5000000);
    return 0;
}

Answer 1

Try tcflush(STDIN_FILENO, TCIFLUSH) before exit().

---

According to tcflush(3):

int tcflush(int fd, int queue_selector);

tcflush() discards data written to the object referred to by fd but not transmitted, or data received but not read, depending on the value of queue_selector:

TCIFLUSH : flushes data received but not read.
TCOFLUSH : flushes data written but not transmitted.
TCIOFLUSH: flushes both data received but not read, and data written but not transmitted.

Answer 2

curses provides a function for this, called flushinp:

The flushinp routine throws away any typeahead that has been typed by the user and has not yet been read by the program.

Your two program fragments do not show this, but the ncurses manual page's section on initialization suggests that you turn off echo (by curses) initially:

initscr(); cbreak(); noecho();

Whether you do that or not, curses actually puts the terminal into raw mode and chooses whether to echo characters typed while your program is running in curses mode.

The first fragment, using getch is a curses function. ncurses attempts to read all input characters into its own buffer, and processes them at the rate your program needs. The flushinp call tells it to discard that buffered input. By the way, your code should use ERR for the check rather than EOF, although for most implementations of curses those are the same numeric value.

When your program stops curses mode (using endwin), it puts the terminal back to the modes where it was initially, i.e., echoing buffered input.

The other fragment of code is not a curses application. The terminal stays in cooked mode (echoing, buffered), and that accumulates in the terminal driver, unread by your program. On exit from the program, the next program (or your shell) gets a chance to read that.

As suggested (rather implied) if your program is not running in curses mode when it exits, you could use the POSIX termios call tcflush to discard the input pending on the terminal, which is what ncurses does (see source).