while loop in matlab password GUI

Hi, i want to create a matlab program that will require the user to enter the username and password before they can gain access to the program. so far i have able to do it if the correct password is enter but i cannot get the program to loop corretly. i want if the user enter the wrong combination of password/username lets say maximum 3 times, the system will terminated. plz help me guys...waste a lot of time on doing this.

username1=*****;
password1=****;
username = upper(get(handles.edit1,'string'));
password = upper(get(handles.edit6,'string'));

if(strcmpi(username,username1))

      if (strcmpi(password,password1))
          disp('successfully log into the system');

     else
         close all
      end

else
       close all

end

Answer 1

[David Sanchez]

Two things: first, you should create a variable (global) called attempts, this variable is initialize at the beginning, right after the GUI is opened. The rest of the code:

% this goes in your login pushbutton callback function
username = get(handles.usrbox,'string');
password = get(handles.psswrdbox, 'string');
attempts = attempts + 1;
if strcmpi(username, username1)&&strcmpi(password,password1)
   disp('b')
elseif attempts == 3
   disp('a');
end

has to be placed on the callback function. Do you insert a login pushbutton? ( A button that has to be pushed in order to login ) If not, the code should be pasted on the edit box callback function (watch out! I guess you have two edit boxes, one for username and another for password, paste it on the password edit box callback ). I would advice to insert a login pushbutton, but that's up to you.

[Pat]

hi this code works..thank you so much for helping me:-)

Answer 2

[David Sanchez]

I hope following code is of help

username1 = 'xxx';
password1 = 'yyy';

attemps = 0;
while attemps < 4
    username = input('intoduce user name: ');
    password = input('intoduce password: ');
    if(strcmpi(username,username1))&&(strcmpi(password,password1))
        disp('successfully log into the system');
        return
    else
        attemps = attemps + 1;
    end
end

[Pat]

thank for your reply, i modified the code a bit to suit my gui. below shown the code that i made but when i try to enter false username and password, the count just go to 3 thus the a value is shown in command window. i just enter the username and password 1 time only. what is wrong with my code

username1= 'xxx';
password1= 'yyy';
attempt= 0;

while attempt < 3

      username = upper(get(handles.edit1,'string'));
      password = upper(get(handles.edit6,'string'));

      if(strcmpi(username,username1))&&(strcmpi(password,password1))
          disp('b');
          return

      else

          attempt = attempt + 1;

      end
  end

disp('a');

Answer 3

[David Sanchez]

Hi, since disp('a'); is outside the while loop, it will always be displayed. You can set a condition if to display 'a' only if 3 attempts were made

username1= 'xxx';
password1= 'yyy';
attempt= 0;

while attempt < 3
  username = upper(get(handles.edit1,'string'));
  password = upper(get(handles.edit6,'string'));
  if(strcmpi(username,username1))&&(strcmpi(password,password1))
     disp('b');
     return
  else
     attempt = attempt + 1;
  end
end
if attempt == 3
  disp('a');
end

I hope it helped you, do not forget to vote if so.

[Pat]

sir i have try the code that you suggested but unfortunately the problem still are there as matlab display the character 'a' although i had only test one fail attempt. i think there are problem in the loop itself as it seem does not wait for user to key in second and third fail attempt before exiting the loop.

Answer 4

[David Sanchez]

Hi, that's a bit awkward, with the code above, disp('a') only comes to work when attempt equals 3 ( if attempt == 3 ). I tested it myself and 'a' is only displayed after three unsuccessful attempts were made. You can try the following version too: ( adapt it for you GUI later, it is easier to debug code outside the GUI, once it works as you want, insert it in the GUI )

username1= 'xxx';
password1= 'yyy';
attempt= 0;

while attempt < 3
    username = input('intoduce user name: ');
    password = input('intoduce password: ');
  if(strcmpi(username,username1))&&(strcmpi(password,password1))
     disp('b');
     return
  else
     attempt = attempt + 1;
     if attempt == 3
          disp('a');
     end
  end
end

[Pat]

sir when i try to use your code it works as expected but as i use the code to my gui it produce same problem as 'a' is displayed although attemp ~= 3. does this mean i need to adjust a bit on my gui?

[Teja Muppirala]

But first change this:

    username = input('intoduce user name: ');
    password = input('intoduce password: ');

To this:

    username = input('intoduce user name: ','s');
    password = input('intoduce password: ','s');

to indicate the input is a string, otherwise you'll have to put quotes in your input to distinguish it from a variable.

[Pat]

mind to share anything that i need to do to adjust my gui to suit this code. i use two edit box, 1 for username input and the other one for the password input. i use this code for username/password input

    username = upper(get(handles.edit1,'string'));
    password = upper(get(handles.edit6,'string'));

Answer 5

[Teja Muppirala]

In your GUI case, the reason it displays 'a' after just one failed attempt is, this loop:

username1= 'xxx';
password1= 'yyy';
attempt= 0;
while attempt < 3
  username = upper(get(handles.edit1,'string'));
  password = upper(get(handles.edit6,'string'));
  if(strcmpi(username,username1))&&(strcmpi(password,password1))
     disp('b');
     return
  else
     attempt = attempt + 1;
  end
end
if attempt == 3
  disp('a');
end

runs 3 times instantly before you can even change the values in the edit boxes. I'm assuming this code is in some callback, like a pushbutton or something. You're going to need to check the password only once every time the user runs this callback function, and keep track of how many times they tried/failed. For example, you might store the variable attempt as 'Userdata' or use SETAPPDATA or something. Then increment it once everytime the user submits the password.

Answer 6

[David Sanchez]

Teja got it right, I think next code would be helpful ( it needs to be adapted to your GUI )

attempts = 0; % do not initialize this variable in pushbutton callback function
% this goes in your login pushbutton callback function
username = get(handles.usrbox,'string');
password = get(handles.psswrdbox, 'string');
attempts = attempts + 1;
if strcmpi(username, username1)&&strcmpi(password,password1)
   disp('b')
elseif attempts == 3
   disp('a');
end

[Pat]

sir where should i paste this code to? it is in the openingFcn or the edit box callback