리눅스 C언어 프로그램 종료후 커널 stdout에 자료 남는것 지우는방법좀알려주세요 ㅠ

#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <termios.h>
#include <stdlib.h>
/* file descriptor for standard input */
#define STDIN 0
 
int main(int argc, char *argv[ ])
 
{	
   	struct timeval tval;	
    	fd_set readfds;	
    	tval.tv_sec = 5;	
  	tval.tv_usec = 800000;
	struct termios initial_settings, new_settings;
	FILE *input;
	FILE *output;
	input = fopen("/dev/tty", "r");
	output = fopen("/dev/tty", "w");
	if(!input || !output)
	{
		fprintf(stderr,"unable to open /dev/tty\n");
		exit(1);
	}
	tcgetattr(0, &initial_settings);
	new_settings = initial_settings;
	new_settings.c_lflag &= ~ICANON;
	new_settings.c_cc[VMIN] = 5;
	new_settings.c_cc[VTIME] = 0;
	if(tcsetattr(0, TCSANOW, &new_settings) !=0)
		fprintf(stderr,"could not set attributes\n");		
 
    	FD_ZERO(&readfds);	
    	FD_SET(STDIN, &readfds);	
    	/* don’t care about writefds and exceptfds: */	
    	select(STDIN+1, &readfds, NULL, NULL, &tval);	
    	if (FD_ISSET(STDIN, &readfds))		
		printf("\nA key was pressed lor!\n");	
    	else		
		printf("Timed out lor!...\n");
 
	tcsetattr(fileno(input),TCSANOW,&initial_settings);
	fflush(stdout);
	fflush(stdin);
    return 0;
 
}