C / C++ / MFC

7-Nov-01 11:50

A while back I posted this question here but no one replied. Let me try again...

I have a console app which prompts the user for a user id and password. The problem is that I don't know how to prevent the password from being displayed as the user types it. I'm using good old cin to retrieve it, like this:

cout << "Password: ";
 
char szPassword[80];
cin.getline(szPassword, sizeof(szPassword));

Is there a way to hide what the user types or perhaps mask it somehow?

Thanks,
Alvaro

C^hris L^osinger7-Nov-01 12:02

C^hris L^osinger

7-Nov-01 12:02

char c = 0;
while (c!=' ')
{
   if(kbhit())
   {
      c=getch();
      printf("*");
   }
}

-c

POKE 808,234

Alvaro Mendez7-Nov-01 12:17

7-Nov-01 12:17

Thanks for the quick answer Chris. Now, to throw a monkey wrench into the solution: it has to compile and run on both Windows and UNIX. Is there an equivalent to kbhit on UNIX?

Thanks again,
Alvaro

Nish Nishant7-Nov-01 13:57

Nish Nishant

7-Nov-01 13:57

Alvaro

In windows you can do this :-

while((c=_getch())!='\n')
{
      printf("*");
      s[i++]=c;
}
s[i]='\0';

For Linux/Unix you'll need to write your own _getch() function.

You can do this with not too much difficulty

(1)First open /dev/tty
(2)use ioctl to change keyboard device parameters [there is some flag to prevent echoing]
(3)Then read one character
(4)use ioctl to set echo back
(5)Now close /dev/tty

I am sorry I couldnt actually put the code here, but if you have access to a unix box you can lookup ioctl and /dev/tty in the man pages and figure out a way.

Regards
Nish

Sonork ID 100.9786 voidmain

Michael P Butler7-Nov-01 22:01

Michael P Butler

7-Nov-01 22:01

Unix/Linux does haven't a getch()!

I'd have thought with all those open source programmers they could get round to doing one of the most basic input functions. I'd have though getch() would have been part of the standard c library.

Michael Smile | :)

Nish Nishant7-Nov-01 22:23

Nish Nishant

7-Nov-01 22:23

Thats cause in Linux they dont take passwords from the keyboard. They put it in a file and put the file in /etc and chown it to root and chmod it to 000

Nish

Sonork ID 100.9786 voidmain

Alvaro Mendez8-Nov-01 5:28

8-Nov-01 5:28

Nish,

Thanks for your reply. I got it working on Windows, which by the way requires me to look for '\r' instead of '\n'. Now I'm trying UNIX but I'm lost:

(1)First open /dev/tty how? with fopen?
(2)use ioctl to change keyboard device parameters [there is some flag to prevent echoing] could not find such flag.
(3)Then read one character how? with fgetc?
(4)use ioctl to set echo back again, I don't know how
(5)Now close /dev/tty I imagine with fclose, but then what, repeat for the next character?

Thanks for your help,
Alvaro

Alvaro Mendez8-Nov-01 6:16

8-Nov-01 6:16

Well, I got it working so that it doesn't show any characters. It's not as pretty as the masked solution, but it's easier and it works. Here's the code for the method, in case someone's interested:

string getPrompt(const char* szPrompt, bool bShow = true)
{
	cout << szPrompt << ": ";
 
	char szResponse[80];
 
	if (bShow)
		cin.getline(szResponse, sizeof(szResponse));
	else
	{
		#ifdef _WIN32
			int iPos = 0;
			for (int c = 0; (c = getch()) != '\r'; )
			{      
				if (c == '\b')
				{
					if (iPos > 0)
						iPos--;
				}
				else if (isprint(c) && iPos < sizeof(szResponse) - 1)
					szResponse[iPos++] = c;
			}
			szResponse[iPos] = 0;
		#else
			system("stty -echo");
			cin.getline(szResponse, sizeof(szResponse));
			system("stty echo");
		#endif
	}

	return szResponse;
}

Thanks for your assistance.
Alvaro

Joaquín M López Muñoz7-Nov-01 12:20

Joaquín M López Muñoz

7-Nov-01 12:20

Not within iostream, I think. You'll have to capture keystrokes with _getch() and print out the asterisks yourself (handling backspaces is a little tricky, also).

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Loops and MFC?

7-Nov-01 11:16

How do i use loops in MFC?
Whenever i use a for loop my MFC program freezes!

thanks Smile | :)

Stan Shannon7-Nov-01 11:24

Stan Shannon

7-Nov-01 11:24

Could you post your code?

"But, daddy, that was back in the hippie ages..." My twelve year old son - winning the argument.

"Stan, you are an intelligent guy who responds in meaningful ways" Paul Watson 16/10/01

7-Nov-01 11:31

heres the code

do
{
if ((x % counter == 0) && (y % counter == 0))
{
x = x / counter;
y = y / counter;
}
counter -= 1;
}
while (counter > 0);

7-Nov-01 11:38

wait.

i figured it out
it was because i was using INT_MAX

how do i use INT_MAX in MFC without crashing or is there an other way?

Alvaro Mendez7-Nov-01 11:59

7-Nov-01 11:59

What do you mean it's because of INT_MAX. Do you mean you're looping INT_MAX times??? That would explain it!

If you don't give your window the ability to process messages (such as mouse clicks) while the loop is running, it will freeze. Write yourself a little function like this:

void AMS_ProcessMessages()
{
	for (MSG msg; ::PeekMessage(&msg, NULL, 0, 0, PM_REMOVE); )
	{
		::TranslateMessage(&msg);
		::DispatchMessage(&msg);
	}
}

And call it inside your loop. That should, if nothing else, prevent your window from freezing.

Regards,
Alvaro

7-Nov-01 14:30

i used INT_MAX for my intial counter value.

int counter = INT_MAX;

and then decreasing the coutner by 1 each time the loop processes