/*
 * program to turn ON echo behavior of the terminal driver
 * idea:
	* open the device file
	* read the termios struct
	* use and operation to turn it (echo flag) on
		to turn it on:  use | with the mask
		#define ECHO	0000010
                                           v
		 M = 000 000 000 000 000 001 000	// the mask as bits
	        FL = 110 011 100 110 101 100 111
	       | M = 000 000 000 000 000 001 000	// the mask as bits
                     110 011 100 110 101 101 111

		info.c_lflag = info.c_flag | ECHO	// long version
		info.c_lflag |= ECHO			// equiv short version

		x = x + 3				// long version
		x += 3;

		x = x / 7
		x /= 7

		y = y * r
		y *= r

		To turn a bit on:

	* write the struct to the driver: using tcsetattr
	* close the device file
 */

#include <stdio.h>
#include <termios.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>

int main()
{
	/// * open the device file
	int fd = open( "/dev/tty", O_RDWR );	// connection to file

	// * read the termios struct
	struct termios tty;			// hold the settings
						// Q:  do we need to open the file?

	int retval = tcgetattr( fd, &tty );			// get the settings
	if ( retval == -1 ){				//  if error, then
		perror("getting settings");
		exit(1);
	}

	// * use and operation to turn it (echo flag) on
	tty.c_lflag |= ECHO;			// equiv short version

	// * write the struct to the driver: using tcsetattr
	retval = tcsetattr( fd, TCSANOW, &tty );
	if ( retval != 0 ){
		perror("Cannot update driver");
		exit(1);
	}

	// * close the device file
	close( fd );
	return 0;
}