asked on

How to turn off characters echoed to the screen from keyboard input

I'm writing a console application that requires the user to enter a password and I would like the program to not echo the input from the keyboard while they enter the password or, if possible, to echo a placeholder like a *.

So I guess like to learn either how to turn off character echo, or how to redirect the standard output.

If it's any help, it's going to be a windows program compiled on MSVC++ 6.0

jkr

Try

BOOL CheckPwd(int nTries,char *pszPwd,char *pszPrompt)
{
int nInput=CR;
int nScrOff=4;
int nOffset;
int nPwdLen;
char *acInBuf;
BOOL bCorrPwd=FALSE;

nPwdLen=strlen(pszPwd)*sizeof(char);

if (!(acInBuf=(char *)malloc(nPwdLen+2)))
{
printf("\n fatal: malloc() failed!\n\n");
abort();
}

memset(acInBuf,0,nPwdLen+2);

for (int i=0 ; i<nTries; i++)
{

printf("\n\n %s",pszPrompt);
fflush(stdout);
nOffset=0;
nScrOff=4;

while(CR!=(nInput=fgetc(stdin)))
{
*(acInBuf+nOffset)=(char)nInput;

if (!printf("%c",'*')
break;
fflush(stdout);

if (nOffset<=nPwdLen) nOffset++;

}

if (bCorrPwd=(!strcmp(pszPwd,acInBuf))) break;

};

free(acInBuf);
return(bCorrPwd);
}

Simply call it like

if (!CheckPwd(3,"mypassword","Password: "))
exit(-1);

which will allow 3 tries ;-)

brettmjohnson

If you are writing a console app, use getpass() defined in conio.h.
If you are writing a GUI app, use a normal edit field and create it with the ES_PASSWORD style.

jkr

>>If you are writing a console app, use getpass() defined in conio.h.

Not available on Win32.

ASKER CERTIFIED SOLUTION

Sys_Prog

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Sarpedon

ASKER

Thanks Sys_Prog.

JKR, You're code still output the text on the screen before outputting the *'s. Not sure if it was just my system.

Just one last thing, If I use getch() and output a * when they type a backspace is taken as a character and a * is output. Is there anyway for me to go backwards in the output?

Sys_Prog

Check for ascii value, if it is baskspace then do not output a *

Example

The following accepts char's in a while loop and stops on entering a escape
Does not print '*' for backspace

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

int main ( void ) {
      char ch ;

      while ( ( ch = getch() ) != 27 ) {
       if ( ch != 8 )
       printf ( "*" ) ;
}
      system ( "PAUSE" ) ;
}