An injector of command into tty, found by me somewhere in the internets and prettified a bit.

ttyc.c

#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>

#include <fcntl.h>
#include <sys/stat.h>
#include <sys/ioctl.h>

#include <string.h>
#include <unistd.h>

void print_help(char *prog_name) {
	printf("Usage: %s [-n] DEVNAME COMMAND\n", prog_name);
	printf("Usage: '-n' is an optional argument if you want to push a new line at the end of the text\n");
	printf("Usage: Will require 'sudo' to run if the executable is not setuid root\n");
	exit(1);
}

struct option {
	const char *name;
	int         has_arg;
	int        *flag;
	int         val;
};

int main (int argc, char *argv[]) {
	char* cmd;
	char* eol="\n";
	int i;
	int fd;
	int newline = 0;
	int mem_len = 0;
    
	int     opt;        /* Option argument container */

	while((opt = getopt(argc, argv, "n")) != -1) {
		switch((char)opt) {
		case 'n':
			newline=1;
			break;
		case '?':
			if(isprint(optopt))
				/* Unknown option */
				fprintf(stderr, "Unknown option `-%c'.\n", (char)optopt);
			else
				/* Non-character option */
				fprintf(stderr, "Unknown option character `\\x%x'.\n", (unsigned int)optopt);
			return 1;
		default:
			abort();
		}
	}

	if(optind >= argc) {
		printf("Usage: %s [-n] DEVNAME COMMAND\n", argv[0]);
		printf("Usage: '-n' is an optional argument if you want to push a new line at the end of the text\n");
		printf("Usage: Will require 'sudo' to run if the executable is not setuid root\n");
		return(1);
	}

	if((fd = open(argv[optind],O_RDWR)) == -1) {
		perror("open DEVICE");
		return 1;
	}

	for ( i = optind+1; i < argc; i++ )
		mem_len += strlen(argv[i])+1;
		
	cmd = malloc(mem_len);
	
	for ( i = optind+1; i < argc; i++ ) {
		strcat(cmd, argv[i]);
		if ( i != argc)
			strcat(cmd, " ");
	}

	for (i = 0; cmd[i]; i++)
		ioctl (fd, TIOCSTI, cmd+i);
	if (newline != 0)
		ioctl (fd, TIOCSTI, eol);
	close(fd);
	free(cmd);
	return 0;
}