how do I remove the scanned number from the terminal so that I can't see it?

Question

I am trying to create a minigame to play with my friends, where someone puts a number, and then we have 10 tries to guess it. Unfortunately, we a number is scanned, it stays in the terminal, so everyone can read and cheat. I also tried to do something kinda dumb, which was use printf("\n\n\n\n\n\n\n\n\n\n\n\n\n...") with 29, but that way the code goes down and looks bad. Can anyone help me?

Answer 1

You didn't specify the platform (OS). In General there are several methods:

• Supressing echo via stty(): See https://stackoverflow.com/a/67709009/6607497
• Using getpass() (obsolete)
• Use terminal escape sequences (like ANSI) to Query the input at a specific line, then erase that line. See https://en.wikipedia.org/wiki/ANSI_escape_code for details.
• Learn to use curses. See http://heather.cs.ucdavis.edu/~matloff/UnixAndC/CLanguage/Curses.pdf for details
• How to disable echo in windows console?
• ANSI C No-echo keyboard input
• https://www.reddit.com/r/C_Programming/comments/64524q/turning_off_echo_in_terminal_using_c/
• https://social.msdn.microsoft.com/Forums/en-US/14220ac4-a557-4cea-b29d-f46222a36ef5/how-to-not-echo-the-input-of-consoleread
• http://www.cplusplus.com/forum/general/3570/
• https://falsinsoft.blogspot.com/2014/05/disable-terminal-echo-in-linux.html
• ...

Maybe you should have searched elsewhere first!

Answer 2

Probably the simplest thing (but certainly not the best)you can do is shell out to stty to manipulate the terminal database. Eg:

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

int
main(void)
{
        char b[32];
        printf("prompt: ");
        system("stty -echo");  /* Turn off echo */
        if( scanf("%31s", b) == 1 ){
                printf("\nyou entered %s\n", b);
        }
        system("stty echo");   /* Turn echo back on */
        return 0;
}

Note that this does not handle signals well, and your terminal may end up with a modified state.

Answer 3

If you use windows, you can specifies the maximum number of commands in the history buffer.:

system("doskey /listsize = 0");

In addition, You can simulate the keyboard shortcut ALT+F7 to clear the history.

See more for windows.

If you use Unix, you can clean the history:

system("history -c");

Answer 4

if you #include <stdlib.h>, system("cls"); should clear the terminal after the number is entered. I tried the game, its fun!