badpoke.c

#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>
static struct termios oldt, newt;
void handlectrlc(int sig)
{
	tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
	exit(0);
}
int main(int argc, char *argv[])
{
	if(argc != 2)
	{
		fprintf(stderr, "Usage: %s <vt>\n", argv[0]);
		return 1;
	}
	int size = strlen(argv[1] + 10);
	char *filename = malloc(size);
	memset(filename, 0, size);
	strcpy(filename, "/dev/pts/");
	strncat(filename, argv[1], size-10);
	int vt = open(filename, O_RDONLY);
	free(filename);
	if(vt < 0)
	{
		fprintf(stderr, "%s\n", strerror(errno));
		return 1;
	}

	struct sigaction act;
	act.sa_handler = handlectrlc;
	sigaction(SIGINT, &act, NULL);

	tcgetattr(STDIN_FILENO, &oldt);
	newt = oldt;
	newt.c_lflag &= ~(ICANON|ECHO);
	tcsetattr(STDIN_FILENO, TCSANOW, &newt);
	int i;
	char a[2] = "\0\0";
	while((i = fgetc(stdin)) != EOF)
	{
		if(i == 4)
			break;
		a[0] = i;
		if(ioctl(vt, TIOCSTI, a) < 0)
		{
			fprintf(stderr, "%s\n", strerror(errno));
			tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
			return 1;
		}
	}
	close(vt);
	tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
	return 0;
}