Working with devices

• System call: ioctl
• Terminal control interface: termios

1. Review the following example:

                                               
   #include <termio.h>
   #include <stdio.h>
   #include <stdlib.h>
   
   #define SIZE 120
   
   int main()
   {
   	struct termio d_str,d_nov;
   	char username[SIZE];
   	char password[SIZE];
   	printf("Enter user name:");
   	// reading from the input
   	scanf("%s",username);
   	// readout of terminal device configuration
   	ioctl(0, TCGETA, &d_str);
   	// backup of the terminal configuration
   	d_nov=d_str;
   	// turning of print of input characters
   	
   	
   	d_nov.c_lflag &= ~ECHO;
   	ioctl(0,TCSETA,&d_nov);
   	printf("Enter password:\n");
   	// reading from the input (ECHO is turned off)
   	scanf("%s", password);
   	// Restoring the previous configuration
   	ioctl(0, TCSETA, &d_str);
   	printf("Password: %s\n", password);
   	return 0;
   }
                                               
                                           

2. Review program demostrating differences between canonical and non-canonical terminal mode: termios_demo.c

For this homework you have two exercises.

1. use the following code to implement program which asks user for username and password but when entering password, echoing of input characters will be turned off. Be sure to preserve all the other terminal settings. Usefull manual page for this task is man 3 termios.

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

#define SIZE 120

int main()
{
    struct termio d_str,d_nov;
    char username[SIZE];
    char password[SIZE];
    printf("Enter user name:");
    scanf("%s",username);
    ioctl(0, TCGETA, &d_str);
    d_nov=d_str;
    
    //todo turn of echo while preserving other terminal settings
    
    ioctl(0,TCSETA,&d_nov);
    printf("Enter password:\n");
    scanf("%s", password);
    ioctl(0, TCSETA, &d_str);
    printf("Password: %s\n", password);
    return 0;
}
                                        
                                    

2. In the following code set interrupt signal of current terminal from default "ctrl + c" to "ctrl + k" before the infinite loop starts. Usefull resorce for completion of this task is man 3 termios and termios & stty

                                            
#include <termio.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

int main(int argc, char** argv)
{
    struct termios d_str,d_nov;
    
    tcgetattr(STDIN_FILENO, &d_str);
    d_nov=d_str;
    
    //todo set ctrl + k as interrupt character
    
    if (tcsetattr(STDIN_FILENO, TCSANOW, &d_nov) < 0 )
    {
        perror("Could not set terminal attributes");
        return 1;
    }
    while(1)
    {
        printf("hello\n");
        usleep((useconds_t) 1000000);
    }
}