user input echo off

This is a discussion on user input echo off within the C Programming forums, part of the General Programming Boards category; I have a program where it accepts user input in a password style, and I don't want to have their ...

  1. #1
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    user input echo off

    I have a program where it accepts user input in a password style, and I don't want to have their password show up on the screen as they type it. How would I accomplish this? I was talking to a few friends and they said something about some asm shellcode redirecting the keyboard output elsewhere, but where I would find such shellcode, baffles me.
    If this is NOT the solution that I seek, please help as well.

  2. #2
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    #include <conio.h>

    int getch();

    FAQ

  3. #3
    Code Goddess Prelude's Avatar
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    >How would I accomplish this?
    Depends on your system. Quite a few Windows compilers support getch and some form of conio.h. On Unix or Linux systems you can fake it using something like this:
    Code:
    #include <termios.h>
    #include <unistd.h>
    
    int setecho(int fd, int onoff)
    {
        struct termios t;
    
        if (tcgetattr(fd, &t) == -1)
            return -1;
    
        if (onoff == 0)
            t.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL);
        else
            t.c_lflag |= (ECHO | ECHOE | ECHOK | ECHONL);
    
        if (tcsetattr(fd, TCSANOW, &t) == -1)
            return -1;
    }
    Code:
    setecho(STDIN_FILENO, 0);
    
    /* Read password */
    
    setecho(STDIN_FILENO, 1);
    My best code is written with the delete key.

  4. #4
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    On Unix systems you can also use getpass from <unistd.h>:
    Code:
    #include <unistd.h>
    
    int main(void)
    {
        char *p;
        p = getpass("Password: ");
    }
    $ENV: FreeBSD, gcc, emacs

  5. #5
    template<typename T> threahdead's Avatar
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    Originally posted by cc0d3r
    On Unix systems you can also use getpass from <unistd.h>:
    Code:
    #include <unistd.h>
    
    int main(void)
    {
        char *p;
        p = getpass("Password: ");
    }
    the function getpass() is obsolete and should not be used anymore.

    better do something like
    Code:
    system("stty -echo"); /* switch echo off */
    system("stty echo"); /* switch it on again */

  6. #6
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    Originally posted by threahdead
    the function getpass() is obsolete and should not be used anymore.
    Can you provide a little more info on that?
    $ENV: FreeBSD, gcc, emacs

  7. #7
    & the hat of GPL slaying Thantos's Avatar
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    Yea and the system() command is sooo great

  8. #8
    Obsessed with C chrismiceli's Avatar
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    --------------------------------------------------------------------------------
    Originally posted by threahdead
    the function getpass() is obsolete and should not be used anymore.

    --------------------------------------------------------------------------------



    Can you provide a little more info on that?
    is says so right in its own man pages!!

  9. #9
    Comment your source code! Lynux-Penguin's Avatar
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    fine... no system...
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <sys/types.h>
    
    
    int spawn(char* program, char** arg_list)
    {
      pid_t child_pid;
      child_pid = fork();
      if(child_pid!=0) //parent process
        return child_pid;
      else //child process (exec_only)
      {
        execvp(program,arg_list);
        fprintf(stderr,"an error has occured in execvp\n");
        abort();
      }
    }
    int main()
    {
      char* list1 = {"stty","-echo",NULL}; //OFF list
      char* list2 = {"stty","echo",NULL}; //ON list
      /* prompt code here */
      spawn("stty",list1); //turn echo off
      /* place code here */
      spawn("stty",list2); //turn echo on
      return 0;
    }
    Asking the right question is sometimes more important than knowing the answer.
    Please read the FAQ
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  10. #10
    Code Goddess Prelude's Avatar
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    >is says so right in its own man pages!!
    Not mine, I use the latest stable version of FreeBSD.
    My best code is written with the delete key.

  11. #11
    End Of Line Hammer's Avatar
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    Originally posted by Prelude
    >is says so right in its own man pages!!
    Not mine, I use the latest stable version of FreeBSD.
    From "IEEE Std 1003.1, 2003 Edition"
    The following features, marked legacy or obsolescent in the base documents, are not carried forward into IEEE Std 1003.1-2001. Other features from the base documents marked legacy or obsolescent are carried forward unless otherwise noted.

    From XSH5, the following legacy interfaces, headers, and external variables are not carried forward:

    advance(), brk(), chroot(), compile(), cuserid(), gamma(), getdtablesize(), getpagesize(), getpass(), getw(), putw(), re_comp(), re_exec(), regcmp(), regex(), sbrk(), sigstack(), step(), ttyslot(), valloc(), wait3(), <re_comp.h>, <regexp.h>, <varargs.h>, loc1, __loc1, loc2, locs
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

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