Solved

How to hide the typed characters

Posted on 2001-09-03
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Last Modified: 2013-12-03
I want to accept the password,so don't want to display the characters.How do I hide this ,I am using C ang Gcc to compile.
Using getch() gives a peculiar error.Says two other library functions are undefined.
Help.
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Question by:rasaraja
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9 Comments
 
LVL 5

Expert Comment

by:garboua
ID: 6453629
why don't you use pam?
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LVL 51

Expert Comment

by:ahoffmann
ID: 6456131
see ioctl()
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Author Comment

by:rasaraja
ID: 6459249
Would you kindly be a bit more descriptive?What's pam ?
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LVL 5

Expert Comment

by:bryanh
ID: 6468955
I assume you're reading the password from a regular tty (terminal; virtual console; X pseudo-tty; whatever).  What causes what you type to display on the terminal is the tty line discipline (basically, a device driver) in the kernel.  You can change this default setting with a command 'stty -echo" (and view the current settings with 'stty -a').  Do a 'man stty' and play around with it.

Stty turns echoing on and off by issuing a TCSETATTR ioctl, via the tcsetattr() library function.  Man tcsetattr (or better, read the GNU C library user's guide) for details.  Your program can turn echoing off with a tcsetattr(), read the password, then turn echoing back on.

As for why getch() doesn't work for you, that's another question and you need to provide more details.  It works for me.

I know little about pam -- I have found it only to be a pain in the butt.  However, it provides library functions that handle the turning off of echoing and many other things.  If it's not too complicated for what you're doing, it might be the right way to go and garboua can give you more information.




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Author Comment

by:rasaraja
ID: 6469299
HI bryanh,

It would be great if u can tell me how I can use getch.I am ready tp provide all the details you require.
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LVL 5

Expert Comment

by:bryanh
ID: 6471233
What library does the compiler (or whatever) complain about being undefined?  Could you post the exact error messages?
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Accepted Solution

by:
acarna earned 50 total points
ID: 6478212
Hi!
Also you could use the getpass() function:

#include <stdlib.h>

char *getpass(const char *prompt);


Note that "getpass" truncates the typed password to at most eight characters.


Regards.

Ariel.
0
 

Author Comment

by:rasaraja
ID: 6481258
Acarna,this is exactly what I was looking for.But it does not seem that getpass() truncates to 8 chars.
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Expert Comment

by:acarna
ID: 6481440
Oh, yes! If you are using a modern Unix maybe the function don't truncate the string but the primitive and old getpass(), you can be sure truncate the data.
Have this in mind in matters as portability.

Regards.
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